I was having a casual conversation with Patricia from Costa Rica who lives at some altitude (5,000 feet, wet Cloudforest) where highs are in the 18-22C range and lows are around 10C, which is relatively close to what we get here during the growing season, including our nightly drizzle and fog. She said that roystonea regia is one of the fastest palms she has. She struggles with other heat loving species that thrive in the lowlands but barely stay alive for her.

Yet the NZ folks tell me roystonea don't grow much for them.

So do roystonea really need hot days and humid nights to grow well? Must say I am quite confused at this point in the contradictory reports.

Don't forget the radically different hours of sunlight and the angle of the sunlight between your location (and NZ) and hers. I don't know exactly how the energy in a leaf is "absorbed," but for solar cells the angle is a critical part of the equation.

Don't forget the radically different hours of sunlight and the angle of the sunlight between your location (and NZ) and hers. I don't know exactly how the energy in a leaf is "absorbed," but for solar cells the angle is a critical part of the equation.

Hi Axel, Hi DypsisDean,

It's clear. Days last 12 hours year round in Costa Rica, with the sun always near the zenith. They are only 9h30 long in Santa Cruz in December, with low sun, poor, pale sun rays.

Besides, even if Patricia has the same average minimum temperature as yours, she probably never experiences near freezing nights. If a royal has a few almost freezing nights, but a very long hot summer like it happens in California, it works.

If it has no long super hot summer, but days which are never short and no near-freezing nights at all, it may work too.

But I'm sure that you understand that you combine all the negative elements: no hot summer, short winter days, low sun and a lot of too-cold nights, including some with near-freezing temperatures (anything below 40°F is cold for a truly tropical climate plant).

Concerning the fact that she has a lot of cloudy weather, mist, fog, etc., don't forget that some of the sun-rays go through it all. Especially if they come down vertically. This is why you can easily heat your water even on a cloudy day, above all in the tropics.

Soil temperature is another important element. Patricia's soil must stay around 62°F (17°C) and only drop to 60°F occasionally. Yours probably goes down to 50°F if not less in winter. This plays also a big big role. She hasn't got any Californian winter.

Still, I would try again if I was you, and provide it with the hottest spot in the property. Experience is the best way to have complete answers. R. borinqueana is another good one to try. Jim in Los Altos kept it alive for a while. Many talented gardeners have excellent result with Bismarkia near SF, so I imagine that one day or another, one of you guys will make it with royals too!

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

If a royal has a few almost freezing nights, but a very long hot summer like it happens in California, it works.

Oups, that was a slip of the keyboard (or possibly my neurons). I meant: "If a royal has a few almost freezing nights, but a very long hot summer as it happens in Florida, it works."

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

It's still a mystery to me. Forget Winter for a second, I can't even get a mm of growth on a roystonea bourinquea in my summer conditions with soil temps well above 62F days fully sunny 70-80F and 52-56F at night. Jim in Los altos lives in the heart of Silicon Valley, lows are much warmer in the Summer.

My parajubaea, ceroxylon, rhopies, hedycepes, kentia, chamadorea,livistona and even dypsis all grow like weeds. I am very pleased with dypsis. Bismarckia and sabals are about the same in speed, very very slow here, which is no surprise. I may be growing the first bonzai bismarckia. But My bourinquea does absolutely nothing.

Roystonea are my wife's favorite palm. I may dump bourinquea and try a Regia.

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

It's still a mystery to me. Forget Winter for a second, I can't even get a mm of growth on a roystonea bourinquea in my summer conditions with soil temps well above 62F days fully sunny 70-80F and 52-56F at night. Jim in Los altos lives in the heart of Silicon Valley, lows are much warmer in the Summer.

My parajubaea, ceroxylon, rhopies, hedycepes, kentia, chamadorea,livistona and even dypsis all grow like weeds. I am very pleased with dypsis. Bismarckia and sabals are about the same in speed, very very slow here, which is no surprise. I may be growing the first bonzai bismarckia. But My bourinquea does absolutely nothing.

Roystonea are my wife's favorite palm. I may dump bourinquea and try a Regia.

royals need LOTS of water. If you dig a hole in sand and don't heavily amend with organics and water copiously in your bone dry summers, it makes sense, little or no growth. Royals grow in swamps or on riverbanks in florida, and mine need lots of water to grow well. If I was going to grow a royal in your high drainage sandy soil(as I understand it) I would make a big hole and amend heavily with organics and some clay. then I would water liberally, and that means dripper plus hose during the hot season. I soak my royals with a hose 2x a week in our dry spring. I have a 6" tall plastic berm driven into the ground around the root zone and flood inside it(40-45 mins of hose). I may remove the berm this year as the roots have expanded. If you had a heavy clay soil it would be much easier...

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

It's still a mystery to me. Forget Winter for a second, I can't even get a mm of growth on a roystonea bourinquea in my summer conditions with soil temps well above 62F days fully sunny 70-80F and 52-56F at night. Jim in Los altos lives in the heart of Silicon Valley, lows are much warmer in the Summer.

My parajubaea, ceroxylon, rhopies, hedycepes, kentia, chamadorea,livistona and even dypsis all grow like weeds. I am very pleased with dypsis. Bismarckia and sabals are about the same in speed, very very slow here, which is no surprise. I may be growing the first bonzai bismarckia. But My bourinquea does absolutely nothing.

Roystonea are my wife's favorite palm. I may dump bourinquea and try a Regia.

Sorry Axel, I can't forget winter for a second. Simply because long winters and cool soils induce complete lethargy. It takes ages for a tropical, heat loving plant to come back from chill induced lethargy. Patricia hasn't got heat. Fine. But she hasn't got long chilly winters and, by consequence, no lethargy!

Even if your soil is around 62°F right now, this only happens during a short warm season. It would take a long season like this to finally stimulate a good growth after an extended dormancy. The problem with your climate (and Tasmania, NZ, Northern Spain, etc) is that when tropical species eventually start to show a modest sign of growth, the summer is already ending. It's late August or September, and the cool season is back again (or will soon be).

This is why so many species languish for ages in such climates and almost do not grow at all.

Of course, there are some surprises and exceptions.

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

It's still a mystery to me. Forget Winter for a second, I can't even get a mm of growth on a roystonea bourinquea in my summer conditions with soil temps well above 62F days fully sunny 70-80F and 52-56F at night. Jim in Los altos lives in the heart of Silicon Valley, lows are much warmer in the Summer.

My parajubaea, ceroxylon, rhopies, hedycepes, kentia, chamadorea,livistona and even dypsis all grow like weeds. I am very pleased with dypsis. Bismarckia and sabals are about the same in speed, very very slow here, which is no surprise. I may be growing the first bonzai bismarckia. But My bourinquea does absolutely nothing.

Roystonea are my wife's favorite palm. I may dump bourinquea and try a Regia.

royals need LOTS of water. If you dig a hole in sand and don't heavily amend with organics and water copiously in your bone dry summers, it makes sense, little or no growth. Royals grow in swamps or on riverbanks in florida, and mine need lots of water to grow well. If I was going to grow a royal in your high drainage sandy soil(as I understand it) I would make a big hole and amend heavily with organics and some clay. then I would water liberally, and that means dripper plus hose during the hot season. I soak my royals with a hose 2x a week in our dry spring. I have a 6" tall plastic berm driven into the ground around the root zone and flood inside it(40-45 mins of hose). I may remove the berm this year as the roots have expanded. If you had a heavy clay soil it would be much easier...

Totally agree. I water my oleracea almost everyday day and they never grew as fast as they did when the irrigation pipe broke and leaked. They like to have their feet flooded, swampy, marshy...

The same can be said about all Roystoneas.

Sonofrans is right, they are heavy feeders: organic material, micro-elements, macro-elements, amino-acids. And they need LOTS of water to be really happy. At least when you grow them outside their typical range, as it is the case here in the Canaries.

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

It's still a mystery to me. Forget Winter for a second, I can't even get a mm of growth on a roystonea bourinquea in my summer conditions with soil temps well above 62F days fully sunny 70-80F and 52-56F at night. Jim in Los altos lives in the heart of Silicon Valley, lows are much warmer in the Summer.

My parajubaea, ceroxylon, rhopies, hedycepes, kentia, chamadorea,livistona and even dypsis all grow like weeds. I am very pleased with dypsis. Bismarckia and sabals are about the same in speed, very very slow here, which is no surprise. I may be growing the first bonzai bismarckia. But My bourinquea does absolutely nothing.

Roystonea are my wife's favorite palm. I may dump bourinquea and try a Regia.

Sorry Axel, I can't forget winter for a second. Simply because long winters and cool soils induce complete lethargy. It takes ages for a tropical, heat loving plant to come back from chill induced lethargy. Patricia hasn't got heat. Fine. But she hasn't got long chilly winters and, by consequence, no lethargy!

Even if your soil is around 62°F right now, this only happens during a short warm season. It would take a long season like this to finally stimulate a good growth after an extended dormancy. The problem with your climate (and Tasmania, NZ, Northern Spain, etc) is that when tropical species eventually start to show a modest sign of growth, the summer is already ending. It's late August or September, and the cool season is back again (or will soon be).

This is why so many species languish for ages in such climates and almost do not grow at all.

Of course, there are some surprises and exceptions.

year round growing season is going to matter a lot. Hawaii has this, but less heat than florida. There is also a big difference in the length of growing season in socal vs florida(longer). I'll bet that Axel's santa cruz location, which has quite a few 90F+ days(30C), gets hotter than a 5k elevation in costa rica, just not nearly as long a growing season. royals grow pretty quickly in Arizona if watered well, no over night humidity to speak of. I think the long cool winters are going to be the biggest hurdle to fast growth. And yet that santa cruz location seems like one of the warmer ones in the bay area, it seems warmer than my coastal OC location at 750'.

It's still a mystery to me. Forget Winter for a second, I can't even get a mm of growth on a roystonea bourinquea in my summer conditions with soil temps well above 62F days fully sunny 70-80F and 52-56F at night. Jim in Los altos lives in the heart of Silicon Valley, lows are much warmer in the Summer.

My parajubaea, ceroxylon, rhopies, hedycepes, kentia, chamadorea,livistona and even dypsis all grow like weeds. I am very pleased with dypsis. Bismarckia and sabals are about the same in speed, very very slow here, which is no surprise. I may be growing the first bonzai bismarckia. But My bourinquea does absolutely nothing.

Roystonea are my wife's favorite palm. I may dump bourinquea and try a Regia.

royals need LOTS of water. If you dig a hole in sand and don't heavily amend with organics and water copiously in your bone dry summers, it makes sense, little or no growth. Royals grow in swamps or on riverbanks in florida, and mine need lots of water to grow well. If I was going to grow a royal in your high drainage sandy soil(as I understand it) I would make a big hole and amend heavily with organics and some clay. then I would water liberally, and that means dripper plus hose during the hot season. I soak my royals with a hose 2x a week in our dry spring. I have a 6" tall plastic berm driven into the ground around the root zone and flood inside it(40-45 mins of hose). I may remove the berm this year as the roots have expanded. If you had a heavy clay soil it would be much easier...

Totally agree. I water my oleracea almost everyday day and they never grew as fast as they did when the irrigation pipe broke and leaked. They like to have their feet flooded, swampy, marshy...

The same can be said about all Roystoneas.

Sonofrans is right, they are heavy feeders: organic material, micro-elements, macro-elements, amino-acids. And they need LOTS of water to be really happy. At least when you grow them outside their typical range, as it is the case here in the Canaries.

Chill induced lethargy is an interesting idea. How does It explain roystonea thriving in higher Winter chill inland SoCal locations? Or even Norcal? There's one in Gilroy in norcal (1200 hours chill annually) that is growing fine and specimens in San Jose also grow well. They get frost burn in the Winter but by Sept they are thriving full crown palms.

All this still doesn't explain the 'lethargy" I see here.

Hi Axel, I believe I've witnessed what others are calling lethargy here. I'm in a similar situations to our NZ growers and yourself; I'll see quite a few cold nights (sub 40F/4C) every winter, but not really anything cold enough to kill a subtropical/tropical palm like a royal outright.

My Dypsis pembana is a perfect representation of what others are calling lethargy. I bought a 200mm pot sized plant (I think what you guys call a 5 gallon...?) from Queensland 2 years ago. I acquired the palm in January, and in the 4 months left of our growing season it powered along, growing 2 full new fronds and a new spear. The D. pembana then came to a complete halt in that July, and by September it was starting to show the negative effects of our long cool winter. As it entered the next growing season it has 2 mostly healthy new fronds and a spear that was on its way. From October to January or perhaps even February, the spear had grown a couple of inches at best. The new spear is now still in the process of opening, as the palm has now completely halted again this winter.

The growth over the same time frame one year later was roughly 1/5 of the rate of the year before. This is what others are calling lethargy and I agree with the reasons for it that others have stated. I cant explain why the Nor Cal specimen hasn't experienced this other than that it may now be more hardened to the winter than it once was. Climates with slightly warmer summers will tend to snap subtropical palms out of their lethargy quicker than climates with cooler summers. Its the reason (I believe) why Dypsis lutescens, decaryi, Roystonea regia, Wodyetia, Bismarkia and others thrive in Adelaide while here they just survive most of the time. Equally the same difference applies between us and Tassie. Chambeys, Cyphophoenix, Kentiopsis, many Dypsis and others thrive here while in Tassie there isn't quite enough summer heat to kick them out of the winter lethargy.

Hi Axel, I believe I've witnessed what others are calling lethargy here. I'm in a similar situations to our NZ growers and yourself; I'll see quite a few cold nights (sub 40F/4C) every winter, but not really anything cold enough to kill a subtropical/tropical palm like a royal outright.

My Dypsis pembana is a perfect representation of what others are calling lethargy. I bought a 200mm pot sized plant (I think what you guys call a 5 gallon...?) from Queensland 2 years ago. I acquired the palm in January, and in the 4 months left of our growing season it powered along, growing 2 full new fronds and a new spear. The D. pembana then came to a complete halt in that July, and by September it was starting to show the negative effects of our long cool winter. As it entered the next growing season it has 2 mostly healthy new fronds and a spear that was on its way. From October to January or perhaps even February, the spear had grown a couple of inches at best. The new spear is now still in the process of opening, as the palm has now completely halted again this winter.

The growth over the same time frame one year later was roughly 1/5 of the rate of the year before. This is what others are calling lethargy and I agree with the reasons for it that others have stated. I cant explain why the Nor Cal specimen hasn't experienced this other than that it may now be more hardened to the winter than it once was. Climates with slightly warmer summers will tend to snap subtropical palms out of their lethargy quicker than climates with cooler summers. Its the reason (I believe) why Dypsis lutescens, decaryi, Roystonea regia, Wodyetia, Bismarkia and others thrive in Adelaide while here they just survive most of the time. Equally the same difference applies between us and Tassie. Chambeys, Cyphophoenix, Kentiopsis, many Dypsis and others thrive here while in Tassie there isn't quite enough summer heat to kick them out of the winter lethargy.

This is very interesting.

Call it lethargy, what you describe sounds more like root rot. When a palm or tropical plant declines two months after Winter solstice that's usually due to root decline from cold wet soil. It will take a while for the plant to recover during the growing season. What Troy experiences is not only root rot but not enough heat even without root rot.

I actually don't have issues with dypsis decaryi, grows well because roots are dry in the Winter. And grows well in cool summer conditions. I wouldn't lump all these palms with pembama. But the common thread surely is root rot. It goes away once palm makes deeper roots.

Just a little note, our minimum temp in the 11 years of living at this place has been 8 C for one night, once. It was out of the ordinary. The normal minimum is 15 C with lows in the 12's C, rarely 10 C, usually in Dec, Jan, and Feb, but for a couple of nights, not continuously. They quickly go back to near 15 C.

Just a little note, our minimum temp in the 11 years of living at this place has been 8 C for one night, once. It was out of the ordinary. The normal minimum is 15 C with lows in the 12's C, rarely 10 C, usually in Dec, Jan, and Feb, but for a couple of nights, not continuously. They quickly go back to near 15 C.

Ok, mystery solved!

Hi Axel,

Mistery is solved, indeed.

Now concerning your doubts: "How does It explain roystonea thriving in higher Winter chill inland SoCal locations? Or even Norcal?"

Well, I mentioned Florida before. They can grow heat demanding species (which are impossible or nearly impossible in SoCal) in 9b, where record temps are much lower than anywhere in coastal San Diego or LA. The reason is clear: more heat, longer summer, longer growing season.

The same thing happens, to a lesser degree in inland SoCal. Many threads in this forum included suppositions about "Where is the right site with the good balance between little frost and enough heat when you go inland?

And actually, it is clear that some palms which are difficult on the coast (because of lack of heat) can make it inland: Attalea, Pseudophoenix, etc. Of course, you have to find a micro-climate with very little frost as their tolerance to sub-freezing temps is limited.

Although Roystoneas grow on the coast in SoCal, they benefit from the heat and more intense growing season inland. The heat season starts earlier, which is a key element to compensate winter lethargy / root rot / leaf damage / etc, so when the plant eventually starts to grow and recover, it still has quite a few weeks of growth ahead.

This is, simply, the reason why they can surpass lethargy, some root rot, leaf burn and other winter stress and damage.

If you don't have these really warm springs followed by marked, long, hot summers, then your plant does not recover in time before autumn (fall) comes.

I hope it may help...

I spend a lot of time in Riverside and there are massive roystonea down the street. There is zero setback in the Winter, in fact they grow right through the Winter. There is no root rot or anything of the sort. I think the conditions in Greece must be different.

Same with roystonea along the coast, solid and robust.

Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter.

I spend a lot of time in Riverside and there are massive roystonea down the street. There is zero setback in the Winter, in fact they grow right through the Winter. There is no root rot or anything of the sort. I think the conditions in Greece must be different.

Same with roystonea along the coast, solid and robust.

Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter.

I still think you have a watering issue. You don't amend your soil much, have very dry summers and have high drainage sand with drip irrigation. All the other species I have seen that grow well for you like parajubaea and brahea etc are not water lovers like a royal. Even royals in florida get skinny trunks and slow growth from under watering. Coastal socal has cool and long winters compared to florida and yet they still grow well there in private yards where they are better taken care of.

I spend a lot of time in Riverside and there are massive roystonea down the street. There is zero setback in the Winter, in fact they grow right through the Winter. There is no root rot or anything of the sort. I think the conditions in Greece must be different.

Same with roystonea along the coast, solid and robust.

Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter.

Axel, I hope you don't mine if I carry on. Just tell me frankly, my only wish is to try to help you thanks to the good and bad experiences I had.

It's just that I see what your climate is like and I am not that surprised that Roystonea are so difficult at your place.

I keep posting because you wrote: "Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter."

You may not have a cold winter, but you have a cool summer.

Cold winter (to a certain extent of course) + hot summer = it works (for example central Florida, inland California, etc.)

Very mild winter + mild, nearly warm summer (like coastal SoCal) = it works too.

But a cool summer like yours, after a long winter = it doesn't work that well.

You wrote: "Same with roystonea along the coast, solid and robust."

Along the coast in SoCal is cool, but not as cool as your place.

Average minimum temp in SD and LA is 10°F higher than yours in winter and 14°F higher in summer. It says it all.

You mentioned Riverside.

You have to take into account that the average minimum temp for the coldest month (January) is 8,5°C / 46,5°F there. It's not that cold! While you have to wait until May to reach that average at your place.

OK, Riverside may experience a few sharp cold snaps, colder than what coastal SF and Monterrey Bay could experience, but the prolonged heat makes it possible for some species in Riverside, while they might not work as well in SF...

Plus average maximum temp for the coldest month in Riverside is a little more than 20°C / 68°F !

So, of course they grow through winter (although it might not be just as fast as in summer).

And, as said before, the winter in such places is probably not cold enough and long enough to make the soil becoming too cold.

Another point: Don't forget momentum. Thanks to warm autumns, palms carry on growing well during the beginning of the winter. I noticed it in many places and observed that it is in late winter and above all in early spring that they are the slowest. It happens here too, I always wish they would grow faster in spring, but they don't. I see some precocious plant (bulbs etc) blooming very early and responding from the slightest improvement of temperature, but many of my ultra-tropical palms stay slow or even dormant sometimes until June!

I had the same trouble in my first garden, in USDA zone 8, with my Sabal minor, as I lived in a region with cold nights year round and cool, short summers...

The same winter with a hot summer, and my minor would have thrived.

The same summer with a mild winter and it would have been happy too.

But my combination was just good for Meconopsis, not Sabals!

Whatever the species, if conditions are too cool for it, it struggles and it takes too long during the (too short) growing season before it starts growing. It may even not grow at all.

Last but not least, Sonoranfans is right to insist on water for Roystonea, especially if you have a fast draining medium. I pointed my experience with my Roystos and the leaking pipe earlier.

I spend a lot of time in Riverside and there are massive roystonea down the street. There is zero setback in the Winter, in fact they grow right through the Winter. There is no root rot or anything of the sort. I think the conditions in Greece must be different.

Same with roystonea along the coast, solid and robust.

Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter.

Axel, I hope you don't mine if I carry on. Just tell me frankly, my only wish is to try to help you thanks to the good and bad experiences I had.

It's just that I see what your climate is like and I am not that surprised that Roystonea are so difficult at your place.

I keep posting because you wrote: "Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter."

You may not have a cold winter, but you have a cool summer.

Cold winter (to a certain extent of course) + hot summer = it works (for example central Florida, inland California, etc.)

Very mild winter + mild, nearly warm summer (like coastal SoCal) = it works too.

But a cool summer like yours, after a long winter = it doesn't work that well.

You wrote: "Same with roystonea along the coast, solid and robust."

Along the coast in SoCal is cool, but not as cool as your place.

Average minimum temp in SD and LA is 10°F higher than yours in winter and 14°F higher in summer. It says it all.

You mentioned Riverside.

You have to take into account that the average minimum temp for the coldest month (January) is 8,5°C / 46,5°F there. It's not that cold! While you have to wait until May to reach that average at your place.

OK, Riverside may experience a few sharp cold snaps, colder than what coastal SF and Monterrey Bay could experience, but the prolonged heat makes it possible for some species in Riverside, while they might not work as well in SF...

Plus average maximum temp for the coldest month in Riverside is a little more than 20°C / 68°F !

So, of course they grow through winter (although it might not be just as fast as in summer).

And, as said before, the winter in such places is probably not cold enough and long enough to make the soil becoming too cold.

Another point: Don't forget momentum. Thanks to warm autumns, palms carry on growing well during the beginning of the winter. I noticed it in many places and observed that it is in late winter and above all in early spring that they are the slowest. It happens here too, I always wish they would grow faster in spring, but they don't. I see some precocious plant (bulbs etc) blooming very early and responding from the slightest improvement of temperature, but many of my ultra-tropical palms stay slow or even dormant sometimes until June!

I had the same trouble in my first garden, in USDA zone 8, with my Sabal minor, as I lived in a region with cold nights year round and cool, short summers...

The same winter with a hot summer, and my minor would have thrived.

The same summer with a mild winter and it would have been happy too.

But my combination was just good for Meconopsis, not Sabals!

Whatever the species, if conditions are too cool for it, it struggles and it takes too long during the (too short) growing season before it starts growing. It may even not grow at all.

Last but not least, Sonoranfans is right to insist on water for Roystonea, especially if you have a fast draining medium. I pointed my experience with my Roystos and the leaking pipe earlier.

Not sure you know enough about California climate to be able to draw the conclusions you are drawing. Some of what you say makes sense. However, Riverside winter average low is 39F. See the western Climate Summaries. It's much colder there at night than at my place. My Jan and feb average highs are 68F and lows are 43F. No comparison to USDA zone 8.

Summer lows are 10F below SoCal, that's the major difference. Should not prevent growth. I will try fixing the water issue.I think that's most likely to be the issue. Jim reports that he failed with several roystonea regia due to Winter root rot, but the bourinquea was unaffected by root rot and actually put on visible growth even in the Winter. His Winters are quite a bit cooler than mine.

I spend a lot of time in Riverside and there are massive roystonea down the street. There is zero setback in the Winter, in fact they grow right through the Winter. There is no root rot or anything of the sort. I think the conditions in Greece must be different.

Same with roystonea along the coast, solid and robust.

Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter.

Axel, I hope you don't mine if I carry on. Just tell me frankly, my only wish is to try to help you thanks to the good and bad experiences I had.

It's just that I see what your climate is like and I am not that surprised that Roystonea are so difficult at your place.

I keep posting because you wrote: "Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter."

You may not have a cold winter, but you have a cool summer.

Cold winter (to a certain extent of course) + hot summer = it works (for example central Florida, inland California, etc.)

Very mild winter + mild, nearly warm summer (like coastal SoCal) = it works too.

But a cool summer like yours, after a long winter = it doesn't work that well.

You wrote: "Same with roystonea along the coast, solid and robust."

Along the coast in SoCal is cool, but not as cool as your place.

Average minimum temp in SD and LA is 10°F higher than yours in winter and 14°F higher in summer. It says it all.

You mentioned Riverside.

You have to take into account that the average minimum temp for the coldest month (January) is 8,5°C / 46,5°F there. It's not that cold! While you have to wait until May to reach that average at your place.

OK, Riverside may experience a few sharp cold snaps, colder than what coastal SF and Monterrey Bay could experience, but the prolonged heat makes it possible for some species in Riverside, while they might not work as well in SF...

Plus average maximum temp for the coldest month in Riverside is a little more than 20°C / 68°F !

So, of course they grow through winter (although it might not be just as fast as in summer).

And, as said before, the winter in such places is probably not cold enough and long enough to make the soil becoming too cold.

Another point: Don't forget momentum. Thanks to warm autumns, palms carry on growing well during the beginning of the winter. I noticed it in many places and observed that it is in late winter and above all in early spring that they are the slowest. It happens here too, I always wish they would grow faster in spring, but they don't. I see some precocious plant (bulbs etc) blooming very early and responding from the slightest improvement of temperature, but many of my ultra-tropical palms stay slow or even dormant sometimes until June!

I had the same trouble in my first garden, in USDA zone 8, with my Sabal minor, as I lived in a region with cold nights year round and cool, short summers...

The same winter with a hot summer, and my minor would have thrived.

The same summer with a mild winter and it would have been happy too.

But my combination was just good for Meconopsis, not Sabals!

Whatever the species, if conditions are too cool for it, it struggles and it takes too long during the (too short) growing season before it starts growing. It may even not grow at all.

Last but not least, Sonoranfans is right to insist on water for Roystonea, especially if you have a fast draining medium. I pointed my experience with my Roystos and the leaking pipe earlier.

Not sure you know enough about California climate to be able to draw the conclusions you are drawing. Some of what you say makes sense. However, Riverside winter average low is 39F. See the western Climate Summaries. It's much colder there at night than at my place. My Jan and feb average highs are 68F and lows are 43F. No comparison to USDA zone 8.

Summer lows are 10F below SoCal, that's the major difference. Should not prevent growth. I will try fixing the water issue.I think that's most likely to be the issue. Jim reports that he failed with several roystonea regia due to Winter root rot, but the bourinquea was unaffected by root rot and actually put on visible growth even in the Winter. His Winters are quite a bit cooler than mine.

I only refereed to data I found, as I believe data are quite often more reliable than personal partly subjective knowledge and feelings.

http://weathercurrents.com/riverside/Climate.do

Still about Riverside, a deeper search gave me indeed lower average minimum temp for January:

43°F here: http://www.weather.com/weather/wxclimatology/monthly/graph/USCA0949

And 41,7°C there : http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca7473

However, please do not sound unfriendly, I only wish to help and try to figure what's the constraint, the problem or impediment which makes it so hard for you to see your Roysto growing...

Before to come back to irrigation, which is decisive, you say that your average max temp for Jan and Feb is 68°F. Then your winters are warmer than inland LA or SD.

It is a very high figure however, as very few official weather stations in Central California have average min temp for these months above 60°F (source: Western Climate Summaries), whether they may be on the coast or inland..

The station with the highest temp is Carmel Valley with 63°F. Higher than this is quite further South...

If you indeed have such data at your place, then you have a fantastic micro-climate, a piece of SoCal in NorCal, which is great. You can actually grow a lot of things.

You wrote: "My Jan and feb average highs are 68F and lows are 43F. No comparison to USDA zone 8."

When I mentioned my first garden in zone 8, I absolutely did not mean that I imagined you were in USDA zone 8!!!

I only wanted to say that the problem of lack of heat is the same everywhere, whatever the species is, when you are too cool for it.

I experienced that in zone 8 with Sabals, I experienced that in zone 10 in the Mediterranean with Adonidia (while Royso grew), I experienced that in zone 10 in Northern New Zealand with Roysto, and I experience that here in zone 11, almost 12, with Licuala orbicularis.

I may grow Cocos nucifera, Areca catechu, Adonidia merrillii, Pritchardia pacifica, Roystonea oleracea, all successfully here, still, I am at a rather high elevation so I'm too cool to grow more equatorial stuff now (even though I grow Roystoneas).

When you say "Summer lows are 10F below SoCal, that's the major difference. Should not prevent growth.". I do not agree that it should not prevent growth. Friends of mine and myself observed that many palms grow more at night than during the day. And it's 10°F of difference, it's a lot...

Another example: in the middle of the island where I am, at the same altitude, they have similar or hotter days, but cooller nights. And it clearly makes a difference in the list of species that they can grow...

Last but not least, again, don't hesitate to give ample and constant moisture to your Roystonea, they need their feet super-wet all the time if you wish a descent growth.

The temperature of the water counts too. If it's only above 70°F during a short summer season, then your Roysto may not like it as it will need more than a few months of super-abundant mild to warm water to stimulate growth, especially if air temp is on the cool side.

Soil temp is crucial as I mentioned above. If the soil is cool for too long at 3 to 5 feet deep, it can be an issue.

But once again, Jim's relative success with R. borinquena gives me hope that you may succeed and I hope you will.

Have you tried R. altissima which is like a kind of sub-species (although it's a true species) of R. princeps?

R. altissima grows at higher elevation, which is fundamental for cool climate tolerance.

Good luck

I spend a lot of time in Riverside and there are massive roystonea down the street. There is zero setback in the Winter, in fact they grow right through the Winter. There is no root rot or anything of the sort. I think the conditions in Greece must be different.

Same with roystonea along the coast, solid and robust.

Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter.

Axel, I hope you don't mine if I carry on. Just tell me frankly, my only wish is to try to help you thanks to the good and bad experiences I had.

It's just that I see what your climate is like and I am not that surprised that Roystonea are so difficult at your place.

I keep posting because you wrote: "Still leaves me puzzled that I can't get mine to grow in the Sumner even without a cold Winter."

You may not have a cold winter, but you have a cool summer.

Cold winter (to a certain extent of course) + hot summer = it works (for example central Florida, inland California, etc.)

Very mild winter + mild, nearly warm summer (like coastal SoCal) = it works too.

But a cool summer like yours, after a long winter = it doesn't work that well.

You wrote: "Same with roystonea along the coast, solid and robust."

Along the coast in SoCal is cool, but not as cool as your place.

Average minimum temp in SD and LA is 10°F higher than yours in winter and 14°F higher in summer. It says it all.

You mentioned Riverside.

You have to take into account that the average minimum temp for the coldest month (January) is 8,5°C / 46,5°F there. It's not that cold! While you have to wait until May to reach that average at your place.

OK, Riverside may experience a few sharp cold snaps, colder than what coastal SF and Monterrey Bay could experience, but the prolonged heat makes it possible for some species in Riverside, while they might not work as well in SF...

Plus average maximum temp for the coldest month in Riverside is a little more than 20°C / 68°F !

So, of course they grow through winter (although it might not be just as fast as in summer).

And, as said before, the winter in such places is probably not cold enough and long enough to make the soil becoming too cold.

Another point: Don't forget momentum. Thanks to warm autumns, palms carry on growing well during the beginning of the winter. I noticed it in many places and observed that it is in late winter and above all in early spring that they are the slowest. It happens here too, I always wish they would grow faster in spring, but they don't. I see some precocious plant (bulbs etc) blooming very early and responding from the slightest improvement of temperature, but many of my ultra-tropical palms stay slow or even dormant sometimes until June!

I had the same trouble in my first garden, in USDA zone 8, with my Sabal minor, as I lived in a region with cold nights year round and cool, short summers...

The same winter with a hot summer, and my minor would have thrived.

The same summer with a mild winter and it would have been happy too.

But my combination was just good for Meconopsis, not Sabals!

Whatever the species, if conditions are too cool for it, it struggles and it takes too long during the (too short) growing season before it starts growing. It may even not grow at all.

Last but not least, Sonoranfans is right to insist on water for Roystonea, especially if you have a fast draining medium. I pointed my experience with my Roystos and the leaking pipe earlier.

Not sure you know enough about California climate to be able to draw the conclusions you are drawing. Some of what you say makes sense. However, Riverside winter average low is 39F. See the western Climate Summaries. It's much colder there at night than at my place. My Jan and feb average highs are 68F and lows are 43F. No comparison to USDA zone 8.

Summer lows are 10F below SoCal, that's the major difference. Should not prevent growth. I will try fixing the water issue.I think that's most likely to be the issue. Jim reports that he failed with several roystonea regia due to Winter root rot, but the bourinquea was unaffected by root rot and actually put on visible growth even in the Winter. His Winters are quite a bit cooler than mine.

I only refereed to data I found, as I believe data are quite often more reliable than personal partly subjective knowledge and feelings.

http://weathercurrents.com/riverside/Climate.do

Still about Riverside, a deeper search gave me indeed lower average minimum temp for January:

43°F here: http://www.weather.com/weather/wxclimatology/monthly/graph/USCA0949

And 41,7°C there : http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca7473

However, please do not sound unfriendly, I only wish to help and try to figure what's the constraint, the problem or impediment which makes it so hard for you to see your Roysto growing...

Before to come back to irrigation, which is decisive, you say that your average max temp for Jan and Feb is 68°F. Then your winters are warmer than inland LA or SD.

It is a very high figure however, as very few official weather stations in Central California have average min temp for these months above 60°F (source: Western Climate Summaries), whether they may be on the coast or inland..

The station with the highest temp is Carmel Valley with 63°F. Higher than this is quite further South...

If you indeed have such data at your place, then you have a fantastic micro-climate, a piece of SoCal in NorCal, which is great. You can actually grow a lot of things.

You wrote: "My Jan and feb average highs are 68F and lows are 43F. No comparison to USDA zone 8."

When I mentioned my first garden in zone 8, I absolutely did not mean that I imagined you were in USDA zone 8!!!

I only wanted to say that the problem of lack of heat is the same everywhere, whatever the species is, when you are too cool for it.

I experienced that in zone 8 with Sabals, I experienced that in zone 10 in the Mediterranean with Adonidia (while Royso grew), I experienced that in zone 10 in Northern New Zealand with Roysto, and I experience that here in zone 11, almost 12, with Licuala orbicularis.

I may grow Cocos nucifera, Areca catechu, Adonidia merrillii, Pritchardia pacifica, Roystonea oleracea, all successfully here, still, I am at a rather high elevation so I'm too cool to grow more equatorial stuff now (even though I grow Roystoneas).

When you say "Summer lows are 10F below SoCal, that's the major difference. Should not prevent growth.". I do not agree that it should not prevent growth. Friends of mine and myself observed that many palms grow more at night than during the day. And it's 10°F of difference, it's a lot...

Another example: in the middle of the island where I am, at the same altitude, they have similar or hotter days, but cooller nights. And it clearly makes a difference in the list of species that they can grow...

Last but not least, again, don't hesitate to give ample and constant moisture to your Roystonea, they need their feet super-wet all the time if you wish a descent growth.

The temperature of the water counts too. If it's only above 70°F during a short summer season, then your Roysto may not like it as it will need more than a few months of super-abundant mild to warm water to stimulate growth, especially if air temp is on the cool side.

Soil temp is crucial as I mentioned above. If the soil is cool for too long at 3 to 5 feet deep, it can be an issue.

But once again, Jim's relative success with R. borinquena gives me hope that you may succeed and I hope you will.

Have you tried R. altissima which is like a kind of sub-species (although it's a true species) of R. princeps?

R. altissima grows at higher elevation, which is fundamental for cool climate tolerance.

Good luck

Sebastian, your advice is spot on, no issues. I am just trying to apply a bit of reductionism and decompose the limiting factors into the different buckets. As for the California climate, a lot of these commercial weather sites publish unreliable numbers. To get an accurate read on the California climates, check out the US National Weather Service's Western Climate Summaries at http://www.wrcc.dri.edu/climsum.html. As for my microclimate, it has to do with my south facing exposure, which raises temperatures by quite a bit. We get regular spells of 75-80F temps in the middle of Winter. It's usually only about 68-72F around everywhere else at that point, but my garden is a southwest facing "bowl" so it just heats up, with the sun angle perpendicular to the ground due to the slope. This is what drives the averages up. I grow some 40 varieties of citrus and they rival in quality to what you can get in Riverside. My chamberyonia put out a new leaf in late January this past Winter.

The limiting factors on roystonea that I know of are:

1) Lack of heat units

2) Too much Winter rainfall leading to root rot (Visible via decline about 60 days after Winter solstice)

3) Frost

What I don't know is if low overnight lows are also a limiting factor for roystonea. They are a limiting factor for many other tropicals. I think this is what no one can really answer. I get that a roystonea will get slowed down to a crawl if it's gonna get hit by root rot every Winter. Tim hit the nail on the head, and I usually avoid palms that can't take our cold Winter soil to the point that they just sulk. But there is a way around that, you just have to start with a bigger palm with more roots. I get good Summer growth on my lucuala, and they remain bone dry in the Winter, hence no issues with root rot.

The roystonea bourinquea I brought up from Socal this Spring hasn't grown at all, I ended up pulling it out and potted it back up. It's not because we had a cold Winter, it didn't spend the Winter here. I will experiment with really soaking the roots to see if I can get it jump started. This is really what's at the center of this entire question.

Hi Axel,

So your Roystonea was planted this spring. The picture is becoming more clear.

Some palms take quite a while before they show signs of growth after being planted. Even if they are planted in spring (which is best, of course).

I don't pay attention to it any more, as I believe now (though I am not 100% sure) that they try to focus on the restitution of their unbalanced root volume (too small) due to the fact they were grown in containers.

I noticed that with many palms in different places. After a year or two of little to no apparent growth, they eventually start to grow well. It's like if they put all their energy and growth in the root system first, which is good in some way, even if, as gardeners and plant lovers, we can't wait to see aerial growth...

As I told you, friends of mine and myself observed (I mean on the shoots and recorded on notebooks) that quite a few palms grow faster at night. And the two more obvious cases were Archontophoenix alexandrae and Roystonea regia in Portugal. Interesting, no?

Try to soak it and feed it like crazy, avoid cold water, and I'm sure you know how to give it the best micro-climate.

I was depressed when I heard Jim lost his. But I found it was a very promising experience anyway so I really wish you will make it.

Hi Axel,

So your Roystonea was planted this spring. The picture is becoming more clear.

Some palms take quite a while before they show signs of growth after being planted. Even if they are planted in spring (which is best, of course).

I don't pay attention to it any more, as I believe now (though I am not 100% sure) that they try to focus on the restitution of their unbalanced root volume (too small) due to the fact they were grown in containers.

I noticed that with many palms in different places. After a year or two of little to no apparent growth, they eventually start to grow well. It's like if they put all their energy and growth in the root system first, which is good in some way, even if, as gardeners and plant lovers, we can't wait to see aerial growth...

As I told you, friends of mine and myself observed (I mean on the shoots and recorded on notebooks) that quite a few palms grow faster at night. And the two more obvious cases were Archontophoenix alexandrae and Roystonea regia in Portugal. Interesting, no?

Try to soak it and feed it like crazy, avoid cold water, and I'm sure you know how to give it the best micro-climate.

I was depressed when I heard Jim lost his. But I found it was a very promising experience anyway so I really wish you will make it.

This is very interesting. Last Spring I took it upon myself to balance out my garden. As many novice palm aficionados often do, I focused primarily on pinnate palms the last 15 years. Mostly parajubaea, phoenix, ceroxylon, rhopies, dypsis, chamberyonia, archontophoenix, and so on. I really had only a handful of palmate palms. Therefore I did a mass planting of palmate palms this Spring. I used mostly brahea, livistona, and sabal to fill in, plus 7 different bismarckia. I put growth marks on them all, and you are right, they are pretty slow, even slower than my dypsis. My fastest bismarckia only put on several inches of growth so far, and new fronds are opening very slowly. My sabals are doing the same thing. Braheas, on the other hand are growing gangbuster, meaning they're rapidly putting on new fronds. In the time one frond barely opens on my sabals and bismarckia, the brahea will put on two plus a fully grown new spear. The speed is amazing.

I suppose it's too early to make a call on how limiting lack of Summer night heat is on some species. On the other hand, for ceroxylon, hedycepe, kentia, parajubaea and rhopies and the few highland geonoma (schottiana and undata), the cool nights are a definite growth accelerator.

Brahea are definitely amongst the best and most dependable palms for awesome results in climates similar as yours. I may live in a place where coconuts grow, I won't snub or forget such beauties.

I went into ecstasies, thanks to these picturesque palms, when I worked in the Mediterranean.

B. armata, B. edulis, B. brandegei, B. nitida...

You just can't go wrong with these. They rarely show signs of deficiencies, they are rarely sun or wind-burnt, they are xeric, almost always look perfect, handle unsteady or extreme weather, etc.

You know all that of course, but I wish all palms had these qualities!!!

And, you are right, they are reliable, satisfying growers, which rarely stress and adapt quickly to their new home.

Many folks complain here that they are not as fast as the routine Washingtonia robusta, it's sad as they are not that slow in the end and they look stunning even when young, especially in the upcountry on the dry leeward side, where they simply thrive and do not suffer from the white moth which attacks them on the coast.

But I am moving away from the original subject...

Back to the Roystonea, here is a photo of one of my oleracea. Note that I am at the upper altitudinal limit for this species. (R. regia grows well even at higher elevation here, up to 2300 feet / 700 meters, while oleracea is visibly not a cool tolerant species)

I planted this oleracea more than a year ago, and it hardly made a new leaf last year. While it finally sends new shoots this year (it woke up only these last few weeks).

To give you an idea, the damage seen on the leaves comes from the transport, as it suffered a lot during shipment.

On the other hand, I have no problem with Wodyetia which only waits during a few months and starts to grow quickly...

Of course, I imagine they may never have this kind of issues in Hawaii, but it's another story there.

As said before, I have that feeling that some palms focus on their root system development first, before they eventually show apparent signs of growth in the form of new leaves.

But that's only a supposition.

Water, water...

I forgot to tell you that when I climbed up today on the terrace where that oleracea grows to post this photo, I took advantage of the opportunity to water it with a hose (note that there are different irrigation systems up there: sprayers and drippers!). I always do it, always, when I go up there, no matter what the reason is (picking up guavas, collecting some basil or parsley, etc).

These thirsty palms never have too much water!!!

Here is a photo I took yesterday while I visited a friend. He told me his neighbour left his house and that part of the neighbours garden is not watered anymore. You can see it straight away with royals!

We had a very rainy spring, which is quite unusual here, but still, one dry summer (which is just normal in the Canaries, even on the green forested Palma) and the royals look dreadful! Poor things.

When you plant a royal you have to wait a year for it to establish roots underground. the first year is slow, even for a big one. They are also the thirstiest palms I grow in my sandy soil, no water, no growth. the second and third summer will show you what growth will be. When you have a fat trunk it means that palm is getting plenty of water. I see ones with fat and thinner trunks all around Bradenton. The thin trunks have smaller crowns, grow slowly and often are planted around masonry or neglected in a public places where irrigation may have ceased. That said, Im not surprised that Axels braheas are outgrowing them, Id bet the braheas are very happy with the limited moisture in the soil.

Axel,

If you have electricity in your garden, why don't you wrap some heating cable around the trunk of the roystonea?

If you heat it during the night you will see if your cool nights are the limiting factor. You will know it within 48 hrs.

Im in Holland (52N) and the only way to let my queen survive a dutch winter is by wrapping the trunk with a heating cable.

It pushes new growth every night during winter even at temps of 18F. Our lightlevels are incredibly low in winter and it was only planted spring 2012.

Edited July 22, 201312 yr by Axel Amsterdam

Axel,

If you have electricity in your garden, why don't you wrap some heating cable around the trunk of the roystonea?

If you heat it during the night you will see if your cool nights are the limiting factor. You will know it within 48 hrs.

Im in Holland (52N) and the only way to let my queen survive a dutch winter is by wrapping the trunk with a heating cable.

It pushes new growth every night during winter even at temps of 18F. Our lightlevels are incredibly low in winter and it was only planted spring 2012.

'

That's not a bad idea. I may also try a regia, I have a feeling the bourinquea may actually be more difficult to grow.

Axel Amsterdam had a good idea which could help to find out... Cool.

Axel, I'm sure you read that Jim in Los Altos mentioned in another post that a California grown royal might have better chance of survival, compared to a plant grown in Florida.

I think he's quite right.

But I just wanted to mention it in this post, in case it may help others who read it and face similar problems, now or in the future, so they would have all the information together.