Cold-frame Greenhouse Question:

[osideterry]

Now that it's cooling down, I've actually finished off by putting plastic on the back of the screen door to up the daytime temps. My greenhouse is in shade until about 1pm, and so the palms can handle the half-day of sun (with 30% shadecloth). I'll keep monitoring the highs, and prop the door open during Santa Ana events.

Now for the question... My daytime highs are 10-20F higher in the greenhouse, but the morning lows are roughly the same as those outside. Is exposing your palms to a possible temperature range of 35F to 85F in the same day bad for palms? Do palms like Dypsis saintlucei, ambositrae, etc. go more or less dormant when the lows drop into the 40s, even if the highs are 70F-80F+?

This is my first time heading toward winter with the greenhouse, and I just started wondering about this.

[Jonathan]

Terry,

my one leaf seedlings of ambositrae, onilahensis and baronii survived without loss of vigour through this winter in my unheated polytunnel, which is basically open to the elements at one end. They are all pushing new leaves now, some of the baronii's grew slowly over winter as well. Larger plants of D. decaryi and D. decipiens kept growing, albeit slowly.

Like your greenhouse, mine has large temperature swings throughout the day, often from around 35F to 75F or more, on a sunny winter day.

I wouldn't know about D. saintlucei, cause I dont have any, but I reckon you'd be fine.

Pritchardia hillebrandii and Beccariophoenix alfredii seedlings the same size also performed well under these conditions, plus a heap of more cool hardy species like Hedyscepe, Lepidorrhachis, Rhopies, etc.

Cheers,

Jonathan

[LJG]

Terry, palms seem to be fine with it. What I have found that do not like the huge temp shifts are some tropicals plants and trees. First year no heat, lost lots of things. Second year heated my greenhouse and had no issues with tropicals. Not sure, could just be me. Seriously.

[BS Man about Palms]

Terry- I suspect your greenhouse would be similar to mine. I have had zero trouble during the winter. (probably because I tend to underwater anyway)

Almost all my greenhouse issues I have traced to "baking" my palms in the spring/summer when it is cool in the morning when I leave for work in the morn and cool on my return. Staying home a couple days showed me that the greenhouse was hitting 110F on some of those days... Now I leave it open during spring/summer.

[Little Palm]

Guys, try creating a vent at the top /gable of your greenhouse (both ends) so the heat does not build-up so much during the day. Keeping the door open helps but heat rises, just a thought. Also, you may want to have your irrigation come on for a few minutes in the middle of the day to cool things down a bit.

Good luck & happy growing,

LP

[MattyB]

There's a lot of finer points of temp and humidity regulation regarding greenhouses and cold frames but you'll figure those out soon enough. The more important issue is the fact that you're getting it to heat up during the day, even if it's freezing at night. That is not a problem and is exactly why you have the cold frame. That daytime heat will allow you to keep your seedlings growing right through winter no matter how cold it gets because you're getting it to heat up during the day. You'll find that you're growing small seedlings at 3 times the rate compared to just keeping them in the shade sitting on your patio. I think that a cold frame is a must for any serious palm grower in SoCal who is on a budget and/or wants to start with smaller sized plants. You'll wonder how you got along without it. I've been growing Pinanga speciosa for three years from a 1 leaf seedling in my cold frame. It's first year it saw 37F with ice on the interior of the plastic. But even on that day it heated back up to the upper 70's in the cold frame and the palm continued to grow. It's like changing your climate from Mediterranean to South Florida. Even if they get cold, it'll be warm again very soon so they can get away with much more than us.

[osideterry]

Thanks guys. Whatever it takes to extend Summer for my seedlings. Of course today is supposed to be in the 80s. It will be interesting to see how hot it gets in there.

[osideterry]

Reviving this thread with one related question:

I have two palms in my cold frame I have no business growing, an Adonidia (5 gallon) and a Areca vestiaria (1 gallon). Tonight the overnight low is supposed to be 40F. These two palms did fine in the greenhouse last year experiencing 35F once and upper 30s a few other times. Are these two palms fine with occasional temps in the 30s, as long as they experience high humidity most of the time?

(If a freeze is in the forecast, I'll bring them inside.)

[Matt in SD]

Hi Terry,

I didn't see this thread the first time around. Like Len, I've also found that palms don't mind the cold nights and warm days. They definitely slow down when the nights are cold, but you get faster growth and better survival rates in the coldframe from the warmer daytime temps. But for some other tropicals, mainly bananas, I had problems in the coldframe. I assumed it was because the warm days tricked them into trying to grow, but the cold nights killed them. I have much better luck with bananas outside...they don't grow in winter and don't look too great, but they survive better.

Regarding your more tender palms, since they survived down to 35F last winter, that should answer your question. Adonidia should not be hard to grow in a coldframe. Areca vestiara is tougher, but a healthy plant should make it. I've got an Areca macrocalyx going into it's 2nd winter in my coldframe, saw 40F last winter which should have killed it, but it never skipped a beat. It's a big 5g now, and perfect looking. Sometimes you just get lucky with a particular plant.

Matt

[Tyrone]

My cold frame is butted up against a large NW facing brick wall of my house. I'm in the southern hem so that wall warms up summer and winter. Basically it has it's own thermal mass, slowly releasing it's warmth when the sun goes down. I find that I can keep my mins up maybe 5 to 7C above ambient temps in there summer and winter which means on average I'm 13C in winter and 23C min in summer. If you can build some thermal mass into the equation you'll up your min's as well with no added heat.

Best regards

Tyrone