Effects of low humidity?

[David_Sweden]

My main question is: What effects and early symptoms do you see on palms in low humidity?

Background:

I'm in the minor league when it comes to palms, still, trying to get palms and other exotic plants to prosper indoors in northern Europe (at 55 degrees north - for you in America that would be like in the middle of Canada, like Edmonton) is a bit of a challenge. I recently got tired of plants dying on me so I've read up on the subject a great deal and instead of buying whatever the local plant shops decide to import, I've selected palms that don't mind less light so much (and have some history of being used indoors), and imported some myself.

It seems I can do much to meet the plants' requirements in most areas (sunny enough position in summer, good enough artificial lights in winter, learning how to water and fertilize properly and select suitable soil) but there is one thing I can't do very much about: Humidity. And many of the palms that accept low light are used to high humidity (living in undervegetation of tropical rain forests).

Since 3 weeks I have one 4' Licuala Ramsayi and a small Livistona Rotundifolia, and one Licuala Peltata seedling just got here, other than that I have a 10 years old Kentia (which is surprised at the unusual amount of attention it is getting since recently and seems to like it very much), some other exotic plants (Jatropha Podagrica, Hawaiian Palm, Ponytail, Dracaena Fragrans, Yucca) and I aim to get one big specimen of either Arenga engleri, Pinanga coronata or Rhopalostylis baueri soon.

This topic is not intended to be on humidifiers since I have already concluded they have no effect in a living area since even the humidity produced by a big aquarium, pebble tray, humidifying machine or placing plants close to oneanother is completely counteracted by ventilation, and you do want ventilation. I even did a number of measurements myself. But there are a few topics in that area that are interesting:

One is misting. Many people say it has no effect and I have already confirmed by measurements that it does nothing for air humidity in a living area. However, I can imagine there might be some good direct effect of water being present on the leaves (never mind the indirect effect of supposedly increasing air humidity) even if it lasts only for minutes. I have as an experiment started to mist all plants (except succulents) heavily (until it drops on the floor quite a lot) once every morning. You might consider it a simulation of dew or rain I guess. I can't be bothered to do it more than once daily in the long run. I'm especially looking at my old Kentia for changes (those leaves have seen a lot of not-so-good treatment, but it looks cool, like a Kentia with a history) but so far I've seen none.

Another is humidity trays (including "pebble trays"). I have this vague notion that it might possibly be helpful a bit the same way misting might be, but in a much smaller scale (the amount of water that leaves a humidity tray per hour is very small, and most of it probably doesn't even reach the leaves). Some swear by this, but has anyone made convincing comparative tests?

And another thing I've been thinking about is whether the worst effect on sensitive palms is those few winter days when humidity can be down to ~10% RH because of very low outdoors temp (not very common where I live) or if the real problem rather is that most days are between 35% and 45% RH (which is close to half of what they'd normally get in a rainforest I think), i e if the low average humidity is the main problem? If the winter days are the biggest issue then I could shut off ventilation those few days (at least for 16 hours per day, maybe more) and add humidity then.

But most of all I'm interested in hearing if anyone can help me identify what it looks like when leaves suffer from low humidity, at an early stage is most interesting so that I can watch out for it, but also what happens later.

Image shows three fronds on my Ramsayi, one of the palms I fear might suffer due to low hunidity (the minor damages on the fronds are from having been in a box during transport from the nursery).

Edited May 7, 2014 by David_Sweden

[Dmcdonald]

What about making a wardian case since the understory palms stay relatively small. You could keep the humidity up and take them out if having a party and want to show off your rainforest plants that look healthy even though they are growing so far from the rainforest.

[Mauna Kea Cloudforest]

Licuala Ramsayi does fine in low humidity, a little midst spray daily will help.

Livistona Rotundifolia would not have been my first choice, Livistona chinensis doesn't mind dry and low light.

Licuala Peltata would also not been my first choice, licuala fordiana is more robust in dry conditions.

[David_Sweden]

Thanks for the input.

The Arenga Engleri is 160 cm already, would have to build a greenhouse.. :-/ Some palms do ok in living areas, I was hoping these would be among them, at least with some special care (not greenhouse though).

Thanks for suggestions of replacements but I already have them so they are memebers of my family already - and the suggested replacements look very different! Sharing a genus doesn't seem to mean much regarding looks, I haven't grasped the genus classifications yet, e g every genus seems to have a palm with fan shaped fronds.. most of which look rather similar. One nice thing with Livistona Rotundifolia is that it looks very pretty even when only 10" tall, much nicer than e g Washingtonia Robusta at that age. I have half a mind to start a thread on which palms that look nice also when small. If you buy a young palm and live up north, you will live with that youngster for years.. My Kentia is shooting up stems 5 to 10 mm per day now though, and that's in my northern window, I think it will do fine.

I read the Rotundifolia does ok in low humidity, it is not an understorey plant I think. Extremely common here, IKEA sells them even.. And in a PDF called "Growing Licuala in Palm Beach County" a guy named Paul Craft says about Licuala Grandis that "it has been used with good success as an interior plant tolerating relatively low humidity" and I thought Peltata was very much related (a dwarf version) but that's about all I know. Wasn't Paul Craft the president of Palmtalk for several years or something, and wrote an encyclopedia on palms?

Anyway, I'm most of all interested in knowing about (early) symptoms of low (air) humidity.

Edited May 7, 2014 by David_Sweden

[LJG]

The damage will be brown tipping. Similar to what you see in plants watered with high salts. The two together can lead to unsightly palms. I think with 45% RH most things will do fine for you. Just avoid the entire leafed palms like Johannesteijsmannia which are sensitive to both issues. I would water with RO water (or water low in TDS) if you want great looking indoor plants. Doing so will limit the damage on the leaves you might see from low humidity.

[DoomsDave]

Hi David, and welcome to Palm Talk.

You ask a great question.

I lived in Ohio and Pennsylvania until I was 25 (almost 30 years ago ), so I'm familiar with the problems of raising indoor plants. The biggest problem with low humidity is in the winter with the heat on. It got dry as Death Valley in my parents' house in the winter and it was hard to keep a lot of plants alive, even if they did great in the summer when the humidity was higher and you could open the windows.

Humidifiers do indeed work better for people than plants. The fundamental problem is that the kind of humidity that a lot of plants like is simply too humid for the inside of your house.

As Len notes, a big problem is brown-tipping, caused by low humidity and salts in the soil.

For salts in the soil, go light on chemical fertilizers, and be sure to set up your pots so you can souse them with water and leach out excess salts once a month or so.

Don't be afraid to experiment with different species. A lot of the Chamadoreas, even though they're native to tropical forests also take the low humidity and low light of houses well, as do Rhapis, Howeas and Laccospadix.

I'd also shoot a PM to Verena on the Board (z4devil) who's in Germany and faces the same issues you do. She's got a great palm garden indoors! http://www.palmtalk.org/forum/index.php?/user/3495-z4devil/ She'll be able to give you super advice, as well as about BMWs . . . .

[bgl]

Hejsan David, och välkommen till PalmTalk - från en gammal malmöit till en annan!

Living in Hawaii, I have little experience with low humidity so will have to leave the advice to those who know more about this scenario. Except to say - now that it's warming up for you, and if it's feasible, you may want to move your palms outdoors, and especially if you're expecting rain. They would love being exposed to actual real rain, and there's no way to replicate this in an indoors situation.

Good luck with the palm growing and I'm looking forward to more of your posts!

Aloha from the Big Island of Hawaii,

Bo-Göran

PS. My sister, who also lives in Malmö, has successfully grown Hyophorbe indica indoors for many years.

[WestCoastGal]

Aside from brown tips, keep an eye out for spider mites on the leaves. Got a bad infestation of them on some plants when I was living in Chicago during the winter. Their population explodes in hot dry indoor air from heaters and they suck the life out of your more tender leaves and it doesn't take long to see the effects on the plant.

Also keep an eye out for scale.

To answer the effects of spider mites, browning at tips initially and yellowing of leaves. If kept indoors, you really should examine the palms with a magnifying glass to catch them early on especially thru the heating season. Once the colony establishes you'll see their webs on the underside of leaflets and around the boots and see them moving on the webs. They can be different colors, red, white, brown... And if it's a bad infestation, hitting the leaflet with a white piece of paper underneath it will knock them to the paper where you can see them better. I had a gorgeous schefflera (non-palm) that was killed off in probably a week despite spraying with Safer Soap. First time apartment with indoor plants and noticed them too late.

[David_Sweden]

Thanks for all the really interesting and useful replies.

Like the tip on "reverse osmosis water". I heard someone recommend distilled water before but that would be a hazzle, but I will check out r.o. machines at the aquarium shop. We have quite soft water though so I don't know how big a difference it would mean.

If it's just minor brow tipping then it doesn't sound too bad. The Licuala Peltata does have big leaves though, it's just a baby, hope it will do fine.

I wonder if it can be diffucult to see the difference in symptoms due to low air humidity and too much direct light? I'm thinking of brown tips and spots. I suppose sunlight and low humidity both are desiccating and I will go easy on direct sunlight (none of that at least the first months).

Great to know the worst issues are during cold winter days, then I know what to focus on and can prepare for it. It should be fine to shut ventilation off for most of each such day, and the stove is 10' from the plants, maybe I can just boil water. I read that humidity in all of Sweden is around 85% in the winter outdoors, problem is when temp outside is low, then RH indoors is the lowest.

Yep I have started to "leach" the soil 2-3 times per year, just leared about that 2 weeks ago. Some advice I read about seems debatable (even some things that many do) but leaching sounds quite reasonable, haven't heard any of my friends do it though.

Hyophorbe indica I hadn't heard can be grown indoors, Hyophorbe verschaffeltii looks nice too I see now and is available at ebay, another great looking genus I'd missed. Just decided on the Rhopalostylis baueri though (and two 80 cm palms from Thailand) so it's kinda full here now, will have to move if I want more greenery.

Bought the Baueri from a German site (Palmeperpaket), they have some advice on humidity that I've tried to translate. In short, they seem to say this in general is a problem during wintertime, one problem is low humidity during season when the apartment is heated and it causes brown leaves and that pest attacks have big consequences (my comment: I do believe mites sleep through the winter, triggered by sunlight) and they recommend frequent misting or a humidifier, it also says that if high humidity and low temp you can get fungus which causes yellowing and drying of cotyledons, and that a fan helps then. Not much new there but still relatively good info.

I know all too well how mites look both in a loupe and the effects of them, I had those bastards recurring for 3 seasons but have been gone for 3 years now. I'm going out of my way to avoid them, e g keeping new plants i quarantine in a separate room for 1 month and examining them about twice per week. It's been unusually sunny the last weeks so I think sleeping mites should have awoken if there were any.

But regarding insects (including scale and mites), if I don't have any in the apartment, then hopefully they won't appear in the winter, more likely get blown in through the window in summer? And if I do get scale, aren't they relatively easy to treat with pesticides or other methods? Mites proved to be quite horrible for me but scale I thought was rather easy to get rid of?

[Z4Devil]

Dear David, so cute that you have thought of me - feel hugged.

Well, David, I have received your pm and - as it would be rude towards you to keep it unanswered - here my experiences.

Generally, Sweden and Germany belong to Europe. But I do believe that Sweden has probably an additional problem: the lack of light in special months.

I am not quite sure if I can help you but let´s discuss:

I do not grow any general palms ... my nature | preference is more special. I always favorize those species that are difficult to get and more difficult to grow, at least at locations they don´t grow normally. My focus is on Lytocaryum, Acanthophoenix and 2 special coconut palms (Samoan and Golden Malayan dwarf [self-germinated].

You can imagine that all of them require more than usual humidity, they are extremely demanding and touchy. For that reason and more.

I always knew what I have to expect and I was and I am ready for the efforts.

What does this mean in detail, especially in relation to your question of humidity?

Take a 2 l - pressure sprayer (boiled water only, not that from the water pipeline of the household), take it and spray as much as possible to the plants, at least once a day.

Acanthos love it, more than direct water in the soil. They are the most difficult palm to grow if you ask me. Never have had such critical palms before. But giving up was and is never a solution.

Lytocaryum is quite easy to grow but loves humidity. They don´t care if you give them a spray once a day, but appreciate it when you spray as often as you can.

Coconut palms are - in this regard - the most difficult palms, indeed. I spray them in the morning and in the evening, on weekends 5 - 10 times a day. And - due to their vulnerability for spider mites - I put them every 2 weeks into a plastic bag and keep them there for 2 days.

On the other hand, if all the mentioned species do not get their minimum of humidity, they will get brown leaf apexes fast, show typical signs of nutrient deficiency and are prone to a lot of damages | deseases.

Best

Verena

[David_Sweden]

Thanks. Sounds like misting probably does have an effect then and even if only once daily.

I'm thinking about water quality now (both when watering and misting), I have soft water so I don't know if it's a big issue here, but someone mentioned "reverse osmosis-filtered water", and I've seen people mentioning distilled water and now boiled water. Does anyone else use R.O filtering or have an opinion on the different water qualities?

When I google osmosis filter or RO filter I get no hits that concern plants, but it does sound like it could be a bright idea. Well I got one hit which said some farmer got magnesium deficiency or something when his water had gone through RO filtering so he had to add fertilizer to fix that, but that's fine I guess. A cheap RO filter (in an aquarium shop) I found costs ~$130, produces 3 litres in less than half an hour, and they said "this cheap version does not remove nitrate" (which apparently is of interest for fish but keeping nitrate sounds fine for plants he and I agreed) so it seems quite manageable.

For now I think I'll go with my tap water but I'll be ready to rush out and get that RO filter if symptoms begin to appear, perhaps it is not likely to happen at least until late autumn.

Edited May 10, 2014 by David_Sweden

[David_Sweden]

Oops too late to edit. One more thought:

On the other hand, both tap water salts, too much fertilizer, and incorrectly balanced fertilizer causes salt buildup in the soil but I have this idea that if I leach the water good 2-3 times per year, it would make requirements less critical on water and fertilizer so that I basically can use tap water and standard fertilizer for all plants (if the fertilizer has all needed components). This applies to watering, not misting, of course.

Sidenote: Another benefit of leaching might be that my cheap moisture meter (which I find very useful even though you can't trust the scale blindly, you have to calibrate it against your fingers..) becomes more reliable (since it basically is an ampere meter connected to a copper and aluminium electrode that turns the soil into a battery while measuring, and more salts can mean more current). I read in some other forum a guy who is very convinced that "perched water" is a main problem for all potted plants and container plants, and the soultion would be to change to a more gritty soil, but I guess that would have the drawback of more frequent watering, and an alternative I think might be to use this cheap moisture meter and keep the soil, especially for palms I don't want to mess with soil and roots if not needed. Almost off topic soon but it's still moisture at least..

[PalmnutVN]

Greetings David!!!

I lived in Växjö for a total of 9 years and spent much of my time attempting to cultivate palms indoors. Indeed, many of the main points have already been covered and I would also just like to reiterate the points made about humidity being important and the scourge of red spider mite.

Nevertheless, I was lucky enough to have one of those glass balconies which were easily heated and I did eventually manage to grow quite a few palms to a standard that was satisfactory in my eyes. The palms that did well included Phoenix canariensis, Neodypsis decipiens, Livistona chinensis, Howea bellmoriana, Chrysalidocarpus lutescens, a Trachycarpus of unknown provenance, Washingtonia filifera and a Rhapis. I used to keep the balcony heated to at least 12-15c during the night/winter and only sprayed to generally keep the rsm at bay. One thing I did do, which hasn't been mentioned yet, was employ the use of some growing lamps, which I used for several hours per day during the cold, dark winters.

Anyway, good luck with your palm growing....

Nick

[David_Sweden]

Thanks for the interesting info. Yes I have intricate sceems on arificial lights that I aim to launch this autumn, aiming at 1-10 klx on all leaves for 16h/day.

I'm hoping spider mites won't find their way into my apartment, I've had new plants in quarantine and inspected them for a month, and the plants closest to the balcony door (where mites possibly might blow in although I live at the 5th floor close to the sea so I hope not many will come this way) have a few feets distance and are selected to be more hardy when it comes to mites and other insects that could infect other plants and are hard to get rid of (Yucca and Phoenix roebelenii closest, Livistona rotundifolia pretty close, haven't decided on Beaucarnea recurvata, and my biggest and rarest plants are not in that room and not in the immediate draft).

It would be interesting to know how often you misted them, or if you perhaps even had some sort of humidifier (since you had a separate glassed-in room it is possible to turn that into a small greenhouse I suppose, unlike inside an apartment).

I've also so far only considered misting from the top, and that's what I suppose a plant is used to, like rain. Don't know if they would appreciate water also on the bottom sides of their leaves.

[Kumar]

Hello David, Here are some experiences from India

I've noticed the effect of RH on some common palms here (native Phoenix, Borassus, Coconut, Areca and caryota)

All do Great! in Bombay and Calcutta (both with RH never below 65-70) with thick, healthy stems, large crown, very green foliage and fast growth (all without care) -- even then the difference in coconut size and growth is visible (with Calcutta not being on the coast directly having a slightly lesser RH)

In Bangalore, the low RH of 30-40 (for 2-3 months) requires some irrigation during that time... those without become noticeably yellow and somewhat slighter build. Royals and Areca don't look too good if uncared for. Only Phoenix seems to be ok if left uncared.

In Delhi (RH of 15-40 for 5-6 months), palms do very badly and 'ordinary' palms look severely stunted with thin stems. Royals and coconuts are rare. Caryota is absent (despite its popularity as a landscaping plant here). Tall Borassus is never seen (I've seen only some small ones). The dry weather seems to suck the life out of most palms (and conversely the conifers do well) Once again, only landscaping phoenix pygmies (a recent trend) seem fine. I'll try to take some photos in Delhi when I go there next.

The effect is obviously most noticeable on the larger specimens

[Sutter Bob]

One palm genus which has done very well indoors for me with daily or every other daily watering is Archontophoenix.

They do get quite a bit of light through a very large north facing window. Ultimately they get tall but the seedlings look good and it takes a number of years before they hit the ceiling.

[David_Sweden]

Thanks that is very interesting. Just so I don't misunderstand you, when you say irrigation Kumar, and watering Bob, do you mean misting, i e spraying water on the leaves? Then it all makes sense. I think those words could just as well mean pouring water into the soil.

And Bob, have you seen that not misting gives symptoms of low humidity on the leaves? I already have the responses from Verena and Kumar which say quite clearly that misting actually helps. Reason I'm asking is that you frequently see advice on misting (How often? Until you have a good conscience apparently. Does it help? Dunno just heard it somewhere..) but as this investigation on humidity in living areas turns out, it seems misting is almost the only way to help plants not content with the humidity. It is also interesting to know how often you mist and if all year round. I know this thread is on symptoms but I can't help asking this as well when I have the chance since it is very useful to know, essential even.

Based on Verena's and Kumar's posts so far it seems once daily is fine when 30-40% RH, and if below that it might be a good idea to take more extreme measures, like several mistings per day, or shutting ventilation off many hours per day and adding humidity from whatever device you have. Not too much work where I live I think (probably beyond what you can be bothered to do in northern Sweden though).

And one more, minor thing is whether to mist also on the bottom sides of the leaves? Do stomata like/dislike being wet, that's a thought (Wikipedia say they open during high humidity & light intensity, which I'll never normally get here, unless misting when sunny). If I'm trying to simulate rain then only top side should be wet, but air humidity is all around, so misting bottom side might possibly be important (or not, maybe even counterproductive for all I know). How does it look in a natural habitat (jungle), does extreme air humidity cause water drops on the leaves? If so then misting both sides of leaves at least can't hurt.

Edited May 12, 2014 by David_Sweden

[David_Sweden]

...did some reading on stomata and if I understand it correctly, palms are all "monocotyledons" (as opposed to "dicotyledons") in which case both sides of the leaves have same number of stomata. In that case I guess I'd better start misting boths sides. Based on what I got from Wikipedia, on which one should of course always be a bit sceptical, but it seemed clear enough.

[David_Sweden]

Hello again. Has anyone tried a professional humidifier indoors, connected to a tap, such as the Minifogger / Hydrofogger? According to my calculations, this can actually keep the air humid while still having normal ventilation (which ordinary humidifiers for home use can not).

They specifically say on their site it is not intended for home use, I'm guessing probably because high humidity constantly can cause mold and that it probably produces small waterdrops which can land on walls and ceiling, but I was thinking that if I put it in the bathroom and leave the door open, and have their humidity sensor to regulate to a modest level of maybe 50% RH, maybe it would be ok? And maybe use it only 8-16h/day.

My palms are doing very well so far in general including the Licualas. The main thing left to worry about is humidity.. :-/

[David_Sweden]

In case anyone reads this old thread in the future maybe I should mention that I ended up using 2 humidifiers with big tanks (about 6L) controlled by a hygrostat aiming at 40-50% RH (I have plants at 2 windows in 2 different rooms so I put one in each). The hygrostats built into humidifiers are always crap, so I bought a type with no electronics so that I can put a hygrostat on the power cord. If you live in Europe you can get the same as me: Hygrostat Trotec BH30 and humidifier Klarstein Toledo.

Also, during the cold months, every morning I boil water at the stove for about 30-45 mins, that is the most efficient way to raise humidity. But you should have at least one hygrometer to make sure you don't risk getting mold (maybe stay below 60% RH but that is up to you). Any cheap digital hygrometer is fine (they all use the same capacitive sensors, with good precision).

Those are the only 2 ways to noteably increase humidity, which you will see yourself when you bought a hygrometer.

And in a normal apartment or house, the ventilation is too strong, you won't be able to get humidity up much at all (which you will also see on the hygrometer). An option is to block or limit the vents and replace it by 5-15 mins of aerating every day. Make sure you aerate then, to not get stuffy air and risk for mold.