Phoenix Sylvestris After Winter

[Northern Tropicals]

Hey guys -- I don't normally post here much.  I normally hang around the Zone Pushers Group on Facebook.  But I wanted to broaden my reach to see if I can get some advice.  As a backstory, I've been zone pushing palms since 2008 here in Wisconsin -- successfully overwintering windmill palms year after year.  I'm on the edge of zone 5b/6a, just north of Milwaukee, WI.  I have my own palm nursery where I currently have over 200 windmill palms in various sizes that I have grown from seed.

Last spring my potted phoenix sylvestris was pushing itself out of a 15/20 gallon pot (the entire pot was like solid roots).  So I decided to give it a go in the ground and the plan was to heavily protect in winter.  I did my standard bulletproof protection as I do my windmill palms (2x2 wood frame box with a layer of plastic sheeting on the interior and exterior of the frame -- serves as a vapor barrier and extra layer of protection, and then on the outside 1 1/2 inches of foam insulation).  For heat I had a 300 watt personal heater plugged into a 35/45 Thermocube and as a backup source, I wrapped C9 lights around the palm also plugged into the Thermocube.  The interior of the box never went below freezing and rarely went above 50 (maybe for short spurts when the sun was out as I left a window so some sun could get to the palm all winter).  The avg temperature of the box was around 40-46 degrees all winter as per my handy dandy wifi sensor. 

I went to unbox it yesterday and was shocked what I found.  All the outer fronds are "bleached out" and dry feeling.  The four unopened spears coming up felt pliable and looked healthy.  But every other frond did not look good.  So now I'm trying to figure out what went wrong as my windmill in the same protection came out flawless.

Here is how it looked in November before I boxed it up.

Here's how it looked yesterday.

And here's a closeup of the spears from yesterday.

 

[Chester B]

Not all palms take to protection as well as Trachycarpus.  The fronds to me seem like they got cooked for whatever reason.   That sort of bleached out look I have seen when palms are exposed to too much cold and is a sort of "Freeze dried" appearance.  But you said they never got cold and they aren't spotting so it doesn't seem like too much humidity.  Were the lights too close to the fronds and sucked the water out of them?

[Las Palmas Norte]

WI is what happened to that palm. 5 zones away from survivability.

[Northern Tropicals]

3 minutes ago, Chester B said:

Not all palms take to protection as well as Trachycarpus.  The fronds to me seem like they got cooked for whatever reason.   That sort of bleached out look I have seen when palms are exposed to too much cold and is a sort of "Freeze dried" appearance.  But you said they never got cold and they aren't spotting so it doesn't seem like too much humidity.  Were the lights too close to the fronds and sucked the water out of them?

That's what I'm trying to figure out.  I had a 25 foot string of C9 lights wrapped around the tied up fronds -- just on the outside and made sure to face the bulbs outwards and not lay on the fronds.  The C9 lights only came on when the Thermocube hit 35 and then back off at 45 degrees.  During the coldest part of winter it would be on 10 minutes, then off 30 minutes or so.  I think the total wattage of the strand was 125 watts.  I had my needle palm tied up and C9 lights wrapped around it and its fine.

[Northern Tropicals]

3 minutes ago, Las Palmas Norte said:

WI is what happened to that palm. 5 zones away from survivability.

Not a helpful response.  As I said in my original post the protection is heavy and never went below freezing.  I've been protecting palms and tropical plants for over 15 years.  Have a good day.

[Northern Tropicals]

Here is how the protection look installed. 

[Las Palmas Norte]

I

Just now, Northern Tropicals said:

Not a helpful response. ...

It's not helpful if your mindset denies reality. Not all palms can be winter protected and survive. After 45 years of exotic gardening has allowed me to realize that.

[Northern Tropicals]

19 minutes ago, Las Palmas Norte said:

I

It's not helpful if your mindset denies reality. Not all palms can be winter protected and survive. After 45 years of exotic gardening has allowed me to realize that.

There's a guy in New York 6b doing it with date palms.

[Chester B]

@Allen any ideas?  It seems like those bulbs might've been too close to the fronds?

[JLM]

Was the palm ever watered during the time in the box? The spear still looks good but that almost looks like a lack of water without direct sunlight to fully brown the fronds. 

[Phoenikakias]

On 4/18/2025 at 7:38 AM, JLM said:

Was the palm ever watered during the time in the box? The spear still looks good but that almost looks like a lack of water without direct sunlight to fully brown the fronds. 

In contrast to  other very experienced member's claims, I think that sylvestris is way thurstier than canariensis and dactylifera. I gow one from seed onwards in my garden ( seed obtained from rps, if this offers any increased credibility about the pureness of the resulted plant), where I cease irrigation from mid December to mid March. Despite the occasional rainfall, I had to water this plant a couple times during winter after a prolonged dry spell. Leaflets became soft and the whole plant looked as if it would shrink.  After a couple hours since watering plant was regaining  its previous rigidity and volume.

[Mr. Clark]

You are REALLY pushing that thing, but if I had to guess, it got desiccated, so, I with JLM on this.   The box was too warm, the air too dry,  and she needed a drink and some humidity.  

I had a random 2-3' Sylvester growing among a row of 12' CT Livistonas I sold late last year.  I was clearing the field for replanting, but just could not bring myself to till the little guy under.  It had been living in the shade, and now was in full sun - I was pressed for time, so I did a terrible job of digging up, and worse job of replanting and irrigating it.  Also, was the worst time of year to transplant here. ..  After a couple weeks, it looked just like your tree, but I got irrigation installed and now a couple months later it's pushing new growth.  

They are super tough trees (except for lethal bronzing, which seems wildly unlikely in you zone, lol!), so I would not be surprised to see some growth this summer.

[JeskiM]

I am going to agree with the dessication idea. Those leaves look more dry than frozen.

My experience with this species is that they want more water than you think, or they are more semsitive to a sudden,  drop off in moisture availability.

While it was under protection, did you see much condensation on the inside of the enclosure ?

If no, then that's some evidence to back up this idea.

Also, cold air is dry air.  It holds far less moisture than warm air, so you need to supply extra water from time to time. A long time at 45 F temps is going to dry the plant out.

Since the inner most leaves look ok, I'd get that palm some water.

-Matt

[Merlyn]

Sylvestris are pretty happy here in the swamp of Floriduh.  Dactylifera is more of a desert palm, and generally looks bad in FL but great in AZ and CA.  That being said, the bluish green color is not too unusual.  I'd guess some additional water now may help it snap back.

[Northern Tropicals]

On 4/17/2025 at 11:38 PM, JLM said:

Was the palm ever watered during the time in the box? The spear still looks good but that almost looks like a lack of water without direct sunlight to fully brown the fronds. 

I think you nailed it.  I didn't water at all after boxing it up.  I treated it the same way as my windmill palm.  I let whatever rain/snow melt around the edge of the box and that's it. 

[Northern Tropicals]

On 4/19/2025 at 1:46 PM, JeskiM said:

I am going to agree with the dessication idea. Those leaves look more dry than frozen.

My experience with this species is that they want more water than you think, or they are more semsitive to a sudden,  drop off in moisture availability.

While it was under protection, did you see much condensation on the inside of the enclosure ?

If no, then that's some evidence to back up this idea.

Also, cold air is dry air.  It holds far less moisture than warm air, so you need to supply extra water from time to time. A long time at 45 F temps is going to dry the plant out.

Since the inner most leaves look ok, I'd get that palm some water.

-Matt

No, wasn't much condensation in box.  Temperature was average low 40s all winter with 60-70% RH in box.  I was actually very conservative because I was trying not to rot it out.  I think it went in the other direction and desiccated.  We had a good soaking rain this weekend.  I raked back the mulch and top inch or two of top soil and spiraled a heating cable around the palm to begin to warm the soil.  I then put the soil and mulch back and plugged it into an Inkbird Thermostat set to 75F.  Trying to get the spears moving as quick as possible.  Daytime temperatures are 50-70 this time of the year and getting warmer each week.

[Merlyn]

@Northern Tropicals a complete lack of watering could sure do it, especially if it wasn't thoroughly rooted into the surrounding soil.  Palms may take 6 months to a year to really grow long roots outwards after planting.  I just transplanted a couple of Gaussia Princeps yesterday afternoon.  They had been in the ground for 3 years and still had a mostly pot-shaped rootball with just a couple of big diameter runners going outwards.  So maybe next winter it will have some roots that extend outwards under the sides of the box.

If you had posted this photo with no other explanation, I probably would have thought "severe dehydration."  The good news is that the rachis/petioles are still green, and the inner leaves & spear look green too.  I'd cut off the oldest set of fronds back up to the end of the dessicated brown part, and leave the rest.  On frostburned palms I've sometimes cut off the dead leaflets with scissors and just left the green spear in place.  It looks ugly but might give more sunlight to the remaining green bits.  More sun to the green = more photosynthesis = faster recovery...maybe?