Zone 8b Woes

[Matthew92]

Hey! new to the site and not really sure where to begin: finally decided to just make a general post about cold hardiness with palms in NW FL zone 8b.

My botanical interests started when I fell in love with the lush northern canopy trees living in Illinois. Moving back to Northern Florida (where I had lived as a child) though, my interest in growing palm trees just took off. After moving back in 2007, I have had a long list of palm and tropical plant endeavor's with many of which never pulled through brutal zone 8b winters.

Here's some detailed experience I've had with some "hot" species that are attempted to be grown here frequently.

Chinese Fan Palm:

For this palm to be satisfactorily hardy in zone 8b is would seem to be quite a stretch. I was so excited as it was my first palm I got: a small (about 3ft) specimen I immediately planted it in the ground. First of all, it grows VERY slowly (from my experience at least), and second, it caves with temps around and below the mid 20's F. My estimate from personal experience is that below 27-26 deg F it really starts to burn. I covered mine each time there was a freeze well into the 20's and even with substantial blankets, it would still get burned sometimes. Although a good point I found with this palm is that it is resilient, bouncing back from freezes, even after being completely defoliated one time. It also came back well after a couple transplants with much root disturbance. Unfortunately mine was finished after the Jan 2014 Gulf Coast Ice storm when we had a coat of ice from freezing rain and the temp dropped to 20 F that night: I hadn't covered it that time though. Through the 6 years I had that palm, it basically stayed the same height.

My observations of other Chinese fan palm specimens in my area of zone 8b has been somewhat similar, with only completely mature trees surviving unprotected. However, these mature trees still suffer horrendous damaged when we do have a harder winter (17-18 deg lowest- completely expected for zn 8b) with the lush fronds being just fried. The only really successful plantings I've seen in this area is when they are planted in a courtyard surrounded by walls. In such a protected spot, they only suffer slight to moderate damage in the harder freezes.

Queen Palm:

The queen palm is seen in many nurseries here in NW FL. Being a new palm enthusiast, I was lulled into getting one to grow this far north: (don't they look so tempting at the nursery with those lush, rich green fronds?) besides, I had seen full grown specimens in the area including a house in my neighborhood that had two with a good 10' of trunk.

In total I went through 3 queen palms with all of them dying. One immature specimen I had was outright killed with a freeze to only the low 20's even though it was very well covered with a substantial blanket.

The first couple of winters at my location (2007-2008 and 2008-2009) were mild and were 9a winters as the temp only got to maybe 22 or 23 at the lowest. That all ended in the 2009-2010 winter where we had a freeze to 17 degrees in February. The mature queen palms I had seen growing in the area all were severely damaged and some killed. The next few winters 2010-2011, 2011-2012, and 2012-2013 were more mild not getting below 20 deg. The 2012-2013 winter especially was easy getting only down to about 23 or so. At this time, I had two queen palms I had been growing in pots. One was getting quite large (for being in a pot at 5 or 6 feet tall) and the other about 2/3 that size. During 2012 I just bit the bullet and planted them in the ground right on the south side fairly close to the house. Although I was away at college that school year, I happened to still be on winter break when the coldest freeze hit in January. Expending all my energy covering my citrus, I let the queens fend for themselves.

At my location, we seem to feel the worst of an area freeze, as I always hit the forecast low and everything really seems to feel it in just about every spot in my yard: even plants on the south side of the house aren't that much better off. So during this freeze I assume these young queens went through low to mid 20's. Amazingly, they had NO DAMAGE! All fronds lasted through till the next summer and kept on growing with the smaller one just shooting up thriving in the sandy soil and abundant rainfall.

And then of course (as most of you on the Northern Gulf Coast know) the 2013-2014 winter rolled along where there was a 17 degree freeze in January (all under clear skies) with the next day staying below freezing basically the entire day, and then the next night had another brutal freeze into the low 20's. It's gotten a little hazy now, but I think on top of this event there was maybe two other times it got into the 20's that winter. Then in late January there was the ice storm. (20 deg with freezing rain coating everything)

Queens gone, and no other queens (even the mature specimens) in the area seemed to survive this.

One of the two aforementioned queens in my neighborhood after 17 degrees, and more than one night into the low 20's (other one used to be on the right side of the front door).

Mexican Fan Palm:

I have not planted one of these in my yard (parents are kind of yard minimalist not wanting many trees unfortunately) but I've carefully watched other specimens in the area. This is barely hardy in zone 8b but is still used very frequently here.

The fronds seem to start burning in the low 20's. Through the 8 winters I've been here, only 3 have had temps that got into the teens. With a winter this hard, unless the tree is fully mature with a full crown, there is a good chance it will be killed. Even still, I have seen fully mature trees decimated and even killed with all fronds burned off. We have just finished our second winter in a row with temps this low and mature trees still have most of the canopy brown and I am getting concern that caliper growth (trunk growth) is going to be hampered.

Healthy, mature specimen on my street during the 2014 ice storm, it has come back since despite basically the entire canopy being burned away.

Canary Island Date Palm:

During the first couple mild winter in my area, I though Canaries were fully hardy here. Starting in 2010 though, I began to understand why this is officially listed as a zone 9 palm.

While many hybrids labeled "Canary Island" are found in nurseries, I happened to obtain what I think was a pure canariensis; it was a small 2-3 feet specimen. Unfortunately I planted it right before the 2009-2010 winter and a 17 degree freeze killed even though it was covered with a substantial blanket.

With the freezes into the teens (especially in 2014), large ones in the area had almost all fronds burned off but most are slowly recovering.

My palm right after planting (was growing quite well in the sandy soil and put out several fronds before it was killed less than a year later)

Date Palm:

This is hardier than canariensis, and I would say this is hardy enough to be dependably grown in zone 8b, even though it will have some damage in a freeze into the teens.

Seems like mainly full sized specimens are planted here in the FL Panhandle. The town I live in is a typical Panhandle town away from the beaches with just scrub oak and pine and the only old palms you'll occasionally see are pindo or sabals. I was delighted when an older lot on a corner of a busy intersection was revitalized with a new bank going in and they went gonzo tropical with the landscaping planting four huge dactyliferas (maybe 25 feet high). This was in 2013, and it endured the following horrendous winter with only maybe a little more than half the fronds being burned. Recovering very well especially for new transplants and have flowered and fruited vigorously since then even while the fronds are still growing back.

Aforementioned palms on corner of intersection, these endured multiple freezes into the low 20's, a 17 degree freeze, ice storm with 20 degrees, and 18 degrees the next winter.

Wild Date Palm:

I planted one (small 2 ft. specimen) and had it for about 3 years. Grew slowly but was making very good progress (maybe growing close to a foot in all directions) and not having much any damage being covered only with a blanket with freezes in the low 20's. Then came the 2013-2014 winter, and was killed (I think it was the ice storm that did it in- and it wasn't covered during that). I believe the sylvestris is only a LITTLE hardier than a Canary, but not as hardy as a dactylifera.

Newly installed specimen couldn't handle freeze to 17 degrees with other nights well down into the 20's.

Pygmy Date Palm:

During the mild winters here, these somewhat survive but inevitably die when a real zone 8b winter come along. Out near the beaches, it seems like people were determined to make them a real landscape staple, but even the slight micro climate out there was not enough to keep them alive during a winter like 2013-2014 where the temp still made it below 20 right at the coast. My grandparents (who live close by) had two 3 stem clumps in front of their house. By the 4th winter or so (despite having covered them during freezes) only 1 stem was left. It was actually a sizable plant by then and about 5 feet tall. They replaced it with a sago (yes it will survive here, but gag me with a spoon, they are so overused now...) So we dug up the remaining plant (with MUCH root disturbance) and put it in my backyard. First of all I don't thing it was doing to hot from the transplant and then another winter with a hard freeze in the low 20's did it in. Pulled out the still green spear to find some kind of larvae on it. Gone

Haphazardly covering a mature specimen with tarp was not enough for this robellini after 17 degrees and other freezes well down into the 20's (deg F).

I am so glad to join this site, tell me what experience you have had growing palms in cold zones! Especially if you live in the FL Panhandle, I would like to compare notes on how these species have fared through these recent hard winters.

Matt,

Edited June 24, 2015 by Opal92

[Matthew92]

Here's a picture of a Chinese fan after 17 degrees in my neighborhood similar sized to the one I had in my yard after 17 degrees.

Edited June 24, 2015 by Opal92

[Matthew92]

Canary in my neighborhood after feeling the full brunt of 17 degrees, showed more damage as time went on to the point of basically the entire canopy being gone: has come back since- albeit slowly.

[NorCalKing]

Welcome!

Excellent well documented post.

I'm not familiar with the panhandle weather, so I'm really enjoying the detailed breakdowns.

[_Keith]

Time for Mule, Butia, Sabal, Needle, Serenoa.

[Sandy Loam]

This is surprising because I, too, am in zone 8b northern Florida, but all of the palms that you listed fare well here. The unusual 2009-2010 freeze event which you mentioned was exceptional, however. Everything around town was damaged, and I even saw a few queen palms die. I saw a couple of canary island date palms completely defoliated and one never grew its fronds back. The owner removed it. However, we can expect another ten or fifteen years to go by before similar freeze events are repeated. We did not get the 2014 freeze the severe way you had it in the western Panhandle. Even Tallahassee did not really have it as the western Panhandle did.

Having said this, the pygmy date palms seem to suffer some damage almost every year here. Their fronds always come back in the spring, but those soft, delicate fronds looked terrible in 2009-2010 for a couple of months.

Are you really 8b every year? Here, we are 8b only sporadically. Some winters are 9b, some are 9a, and some are 8b. A few miles west of town is a cold patch that is almost always 8b. For some reason, moving eastward means warmer temperatures here.

Perhaps my secret is that plant everything too close together, jungle-style. I plant as much as I can under canopy as well. I don't know why dense planting protects my plants, but it seems to work. I don't dare plant anything remotely tender in front of my house because that area is right out in the open with zero overhead canopy. The temperatures on my front lawn seem to be much colder than areas tucked away in my backyard.

Can you experiment with dense plantings? You can't just buy one tree. You would have to buy a whole bunch of trees and other plants and pack them in tightly (too tightly) in a specific area beneath a patch of forest. It also helps if your house is on top of a hill, at least at our low elevation near sea level. My house is at the top of a steep hill, so the cold air drains downward toward a different subdivision when a cold snap hits. ....or so I assume.

[Matthew92]

This is surprising because I, too, am in zone 8b northern Florida, but all of the palms that you listed fare well here. The unusual 2009-2010 freeze event which you mentioned was exceptional, however. Everything around town was damaged, and I even saw a few queen palms die. I saw a couple of canary island date palms completely defoliated and one never grew its fronds back. The owner removed it. However, we can expect another ten or fifteen years to go by before similar freeze events are repeated. We did not get the 2014 freeze the severe way you had it in the western Panhandle. Even Tallahassee did not really have it as the western Panhandle did.

Having said this, the pygmy date palms seem to suffer some damage almost every year here. Their fronds always come back in the spring, but those soft, delicate fronds looked terrible in 2009-2010 for a couple of months.

Are you really 8b every year? Here, we are 8b only sporadically. Some winters are 9b, some are 9a, and some are 8b. A few miles west of town is a cold patch that is almost always 8b. For some reason, moving eastward means warmer temperatures here.

Perhaps my secret is that plant everything too close together, jungle-style. I plant as much as I can under canopy as well. I don't know why dense planting protects my plants, but it seems to work. I don't dare plant anything remotely tender in front of my house because that area is right out in the open with zero overhead canopy. The temperatures on my front lawn seem to be much colder than areas tucked away in my backyard.

Can you experiment with dense plantings? You can't just buy one tree. You would have to buy a whole bunch of trees and other plants and pack them in tightly (too tightly) in a specific area beneath a patch of forest. It also helps if your house is on top of a hill, at least at our low elevation near sea level. My house is at the top of a steep hill, so the cold air drains downward toward a different subdivision when a cold snap hits. ....or so I assume.

Yes, I think you're right about it getting warmer Eastward, and I do think the Western Panhandle took the brunt of these recent winters. And only out of the 8 winters I've been here since 2007 the temp has gotten below 20, so it seems that much of the time we do behave like 9a.

As for planting position, I do have to say that most of my palms have been planted in somewhat exposed locations. My yard is pretty sparse in terms of close trees and shrubs. There is one spot in the backyard that is under more of a canopy and I notice it does help. In fact I was able to have an Australian Tree Fern kept alive for awhile in this spot as well as a Phil. selloum that went through the 2010 freeze and didn't even lose stems.

[Matthew92]

Time for Mule, Butia, Sabal, Needle, Serenoa.

Yes! I'm dying to try others, just not much space in the yard anymore and going to be moving out soon. I will need a nice plot or yard to try them!

Original landscaping was done 15 years ago: had a good designer. For the front yard they did 1 pindo, several windmills, and sagos. Besides a couple windmills that died of unknown causes early on (we think something wrong in the soil) all the rest have done really well. The Pindo especially is turning out to be an awesome specimen.

[Matthew92]

And sorry about all the typos: unfortunately I found out that it will only let you edit once.

[Matthew92]

This is surprising because I, too, am in zone 8b northern Florida, but all of the palms that you listed fare well here. The unusual 2009-2010 freeze event which you mentioned was exceptional, however. Everything around town was damaged, and I even saw a few queen palms die. I saw a couple of canary island date palms completely defoliated and one never grew its fronds back. The owner removed it. However, we can expect another ten or fifteen years to go by before similar freeze events are repeated. We did not get the 2014 freeze the severe way you had it in the western Panhandle. Even Tallahassee did not really have it as the western Panhandle did.

Having said this, the pygmy date palms seem to suffer some damage almost every year here. Their fronds always come back in the spring, but those soft, delicate fronds looked terrible in 2009-2010 for a couple of months.

Are you really 8b every year? Here, we are 8b only sporadically. Some winters are 9b, some are 9a, and some are 8b. A few miles west of town is a cold patch that is almost always 8b. For some reason, moving eastward means warmer temperatures here.

Perhaps my secret is that plant everything too close together, jungle-style. I plant as much as I can under canopy as well. I don't know why dense planting protects my plants, but it seems to work. I don't dare plant anything remotely tender in front of my house because that area is right out in the open with zero overhead canopy. The temperatures on my front lawn seem to be much colder than areas tucked away in my backyard.

Can you experiment with dense plantings? You can't just buy one tree. You would have to buy a whole bunch of trees and other plants and pack them in tightly (too tightly) in a specific area beneath a patch of forest. It also helps if your house is on top of a hill, at least at our low elevation near sea level. My house is at the top of a steep hill, so the cold air drains downward toward a different subdivision when a cold snap hits. ....or so I assume.

Yes, I think you're right about it getting warmer Eastward, and I do think the Western Panhandle took the brunt of these recent winters. And only out of the 8 winters I've been here since 2007 the temp has gotten below 20, so it seems that much of the time we do behave like 9a.

As for planting position, I do have to say that most of my palms have been planted in somewhat exposed locations. My yard is pretty sparse in terms of close trees and shrubs. There is one spot in the backyard that is under more of a canopy and I notice it does help. In fact I was able to have an Australian Tree Fern kept alive for awhile in this spot as well as a Phil. selloum that went through the 2010 freeze and didn't even lose stems.

Meant to say ***out of the 8 winters I've been here since 2007 only 3 have gotten below 20 degrees***

boy, wish it would let you edit after posting

[Alicehunter2000]

Welcome to PalmTalk....trying to figure out where you are located? Defuniak Springs?

Here is a thread on the dreaded 2013-2014 Winter...There are a few of us on here that are intimately familiar with Gulf Coast 9a/8b conditions...too much to cover briefly...do you have a specific palm in mind to try? as others have said...canopy and yard location seem to be key for a lot of stuff up here.

http://www.palmtalk.org/forum/index.php?/topic/40102-polar-vortex-vs-large-palms-in-zone-9a/?hl=%2Blarge+%2Bpalms+%2Bpolar+%2Bvortex

[NorthFlpalmguy]

This is surprising because I, too, am in zone 8b northern Florida, but all of the palms that you listed fare well here. The unusual 2009-2010 freeze event which you mentioned was exceptional, however. Everything around town was damaged, and I even saw a few queen palms die. I saw a couple of canary island date palms completely defoliated and one never grew its fronds back. The owner removed it. However, we can expect another ten or fifteen years to go by before similar freeze events are repeated. We did not get the 2014 freeze the severe way you had it in the western Panhandle. Even Tallahassee did not really have it as the western Panhandle did.

Having said this, the pygmy date palms seem to suffer some damage almost every year here. Their fronds always come back in the spring, but those soft, delicate fronds looked terrible in 2009-2010 for a couple of months.

Are you really 8b every year? Here, we are 8b only sporadically. Some winters are 9b, some are 9a, and some are 8b. A few miles west of town is a cold patch that is almost always 8b. For some reason, moving eastward means warmer temperatures here.

Perhaps my secret is that plant everything too close together, jungle-style. I plant as much as I can under canopy as well. I don't know why dense planting protects my plants, but it seems to work. I don't dare plant anything remotely tender in front of my house because that area is right out in the open with zero overhead canopy. The temperatures on my front lawn seem to be much colder than areas tucked away in my backyard.

Can you experiment with dense plantings? You can't just buy one tree. You would have to buy a whole bunch of trees and other plants and pack them in tightly (too tightly) in a specific area beneath a patch of forest. It also helps if your house is on top of a hill, at least at our low elevation near sea level. My house is at the top of a steep hill, so the cold air drains downward toward a different subdivision when a cold snap hits. ....or so I assume.

Agreed, most do well here as well and I am probably close to a midpoint location between you both. Yes we do have interesting winters with hard frost but everything you listed except the queen and pygmy/ P. roebelleni does well here long term.

I remember that bad winter of 2009-10 and lost a bunch of zone-pushing palms to it. Like Sandy Loam stated, it is more of a rarity. I went deer hunting those few days of 17 degrees and the mud puddles were frozen so thick with ice you could hear them breaking when you drove through it.. which is rare here.

[Matthew92]

Welcome to PalmTalk....trying to figure out where you are located? Defuniak Springs?

Here is a thread on the dreaded 2013-2014 Winter...There are a few of us on here that are intimately familiar with Gulf Coast 9a/8b conditions...too much to cover briefly...do you have a specific palm in mind to try? as others have said...canopy and yard location seem to be key for a lot of stuff up here.

http://www.palmtalk.org/forum/index.php?/topic/40102-polar-vortex-vs-large-palms-in-zone-9a/?hl=%2Blarge+%2Bpalms+%2Bpolar+%2Bvortex

I'm in Niceville. We aren't that far north, but not right on the coast so the freezes seem to just blast right through here before moderating some near the beaches. Again, we hit 17 deg in 2014 and then this past January it got to 18. Just read the thread you linked, and it made me think back to early 2014 and the sentiments I was feeling as well during that time. Like you, many species surprised me and pulled through, but I did lose a lot as well.

I'm interested in much anything different than what is used ad nauseam around here (sabal, sago, pindo, palmetto....) more specifically though on the top of my list are braheas, California Fan Palm, Puerto Rican hat palm, radicalis/hardy bamboo palm, and syagrus/butia/jubaea hybrids (especially mule).

Remind me to post pictures: in front of the Northwest Florida Regional Airport there is a row of Washingtonias; some look very different than others being thicker trunked with more wide, lax leaves. The past two winters, the robustas (thinner looking trees) got totally fried with one or two dying, while the thicker ones (I think some are hybrids, but there are a couple that actually look like pure filiferas!) only got a small amount of damage!

The ones that look like filiferas seem to be doing great in conditions here, and as I saw mentioned in another comment on here, we have crazy drainage in the sandy soil in the Panhandle which may really help. I am thinking that filifera may be a good replacement to robusta.

[Alicehunter2000]

Filibusta's. ....I know where a great source tree is with proven genetics.....it should have seeds pretty soon

[Matthew92]

Filibusta's. ....I know where a great source tree is with proven genetics.....it should have seeds pretty soon

I've been really excited about filibustas, as robusta really is not satisfactorily cold hardy enough along the FL Panhandle. However, I saw another thread on here that someone's filibustas got totally fried in temps basically same as I had this past winter.

I would still be willing to try, and I guess it is possible some "mules" inherit more cold hardiness than others. Although I still have some good hope for pure filibusta in our fast draining soil.

[Matthew92]

Filibusta's. ....I know where a great source tree is with proven genetics.....it should have seeds pretty soon

I've been really excited about filibustas, as robusta really is not satisfactorily cold hardy enough along the FL Panhandle. However, I saw another thread on here that someone's filibustas got totally fried in temps basically same as I had this past winter.

I would still be willing to try, and I guess it is possible some "mules" inherit more cold hardiness than others. Although I still have some good hope for pure filibusta in our fast draining soil.

**meant to say have some hope for pure filifera in our fast draining soil.

[Matthew92]

Filibusta's. ....I know where a great source tree is with proven genetics.....it should have seeds pretty soon

Here's a streetview that barely shows the Washingtonias in front of the NW FL Regional Airport I was talking about: hopefully soon I'll get some good closeups in person.

Here you can barely see where I've circled in red the pure robustas that are tall and thin, and it's hard to see, but there is one in front of the others that was killed in sub-20 deg freezes and is now a stick. Then with the white arrows I've pointed to what I think are pure filiferas. They survived almost undamaged.

Now here's a second shot where you can see the suspected filiferas a little more clearly (white arrows).

[palmsOrl]

Thank you for sharing such detailed information on palm growing in North Florida. I am somewhat surprised that the dates and washingtonias gets that much damage from upper teens, but it is probably due to the lows combined with the cold days and wetness that sometimes accompanies the events. The pygmy date is not an ultra long-term survivor in much of the Orlando area even, though the metro area should no longer lose these to freezes in the future. I have seen some dead around here recently from what I assume is drought or maybe nutrient deficiency or a combination.

Queen palms are a great way to give the FL Panhandle coastal areas a tropical look between severe freezes, as they are inexpensive as palms go.

The northern half of the Western Panhandle (areas such as Crestview) is even colder as many years the area sees low teens. You might as well be in Central or Northern Georgia. Even the Sabal palmetto I have seen in this area look scrawny with small crowns.

[Alicehunter2000]

It's all about the individual genetics of the Washingtonia's in question.....there are ton's of what appear to be straight robusta growing all over Panama City, Panama City Beach and surrounding areas. They have been growing for many years. I've just about come to the conclusion that queens will not make it long term here. There are some that survive....but most don't.

[Sandy Loam]

I think it's all about choosing the right planting location. The tough plants are planted out in the open, whereas the tender plants get planted under larger trees, and all bunched together so that they create their own microclimate.

Hey, the Streilitzia Nicolai in the photo below has been growing for many years in the same climate as yours (in Gainesville, Florida). It is planted in a protected location behind a wall, but it has still seen 17 degrees fahenheit and sailed on through without any more than a few brown-looking fronds temporarily. (click to enlarge) It must be 15 feet tall.

Edited July 17, 2015 by Sandy Loam

[Matthew92]

Finally was able to take some close up pictures of the Washingtonias in front of the airport- as you can see, one of the thicker trunked ones is fruiting. The stick robusta died from the cold, and even the ones remaining still don't have the most healthy and full crowns in the world.

[Matthew92]

I am tempted to say that the one on the left could be an actual filifera.

Edited July 27, 2015 by Opal92

[Matthew92]

Some more of the thicker trunked ones- (filibusta or filifera) although I suspect these pictured here are hybrids. Again, they went through upper teens with minor damage while the pure robustas nearby suffered greatly. If you want a Washingtonia in the colder side of zone 8b that will be dependably hardy, filibusta or filifera is the way to go.

Edited July 27, 2015 by Opal92

[Omeyer72]

Welcome!

Excellent well documented post.

I'm not familiar with the panhandle weather, so I'm really enjoying the detailed breakdowns.[/quote

Completely agree. Very well done...great post, pics and data.

[Brad Mondel]

Those are not pure Filiferas, possibly hybrids. Filiferas have grey-green leaves, thicker trunks, and a more linear frond.

[Matthew92]

Here's some zone 8b "woes:" not looking forward to my "tropical garden" under my window getting fried again this winter. This is from the 2013-2014 winter

Before

After (where you see that board up against the wall is where a pipe burst after 17 degrees and 24+ hours below freezing, good ol' zone 8b winter for ya!)

Before

After

 

[_Keith]

Hang in there, statistically we are due for a mild one, I HOPE!

[Matthew92]

1 hour ago, _Keith said:

Hang in there, statistically we are due for a mild one, I HOPE!

Yes, I hope for nothing below 22 degrees, and it will be well deserved after the last 2 brutal winters in a row.

[enigma99]

On July 17, 2015 at 08:52:39, Sandy Loam said:

I think it's all about choosing the right planting location. The tough plants are planted out in the open, whereas the tender plants get planted under larger trees, and all bunched together so that they create their own microclimate.

 

Hey, the Streilitzia Nicolai in the photo below has been growing for many years in the same climate as yours (in Gainesville, Florida). It is planted in a protected location behind a wall, but it has still seen 17 degrees fahenheit and sailed on through without any more than a few brown-looking fronds temporarily. (click to enlarge) It must be 15 feet tall.

I don't think these have seen anywhere near 17F. My experience they start taking damage below 29-30 or so. At 17, they would look pretty bad. Maybe there was some urban heating and warmth from the building 

[Sandy Loam]

I have had two of them in my yard for about five years. The outer exposed leaves look brown by the end of winter, but I just clip them off and more grow back. They have tolerated any cold that my climate could throw at them since about 2011. 

 

I lost one in October due to root rot (clay soil, planted in wet hole, two years of constant rain).

Streilizia Nicolai don't seem to get damaged two hours south of here in Tampa, Orlando, Sarasota, etc. They also grow to massive sizes down there.  There is one at Selby Gardens in Sarasota which is huge.

[Sandy Loam]

...but the biggest surprise to me was that these Giant Birds of Paradise are so susceptible to wet soil problems.  I was not aware that they prefer dry soil.  I have seen big ones in Southern California. They must love the dry soil there.

[Matthew92]

The 4 P. dactyliferas on the corner of the street mentioned in my first post on this thread are just now beginning to have significant trunk rot (canopies are healthy though). I think it may be from damage/stress incurred in the '13-'14 and '14-'15 winters.