Single polycarbonate greenhouse for palm acclimatization

[Mauna Kea Cloudforest]

I am putting up a greenhouse, and the one that I ended up getting for christmas is an inexpensive single walled polycarbonate greenhouse. At first, I hesitated, wondering if I should make the labor investment in building it, but after some consideration, I do see some upside given what I am trying to grow. I wanted to get people's input on this.

The greenhouse is not meant to create a special environment where I can grow palms that are otherwise marginal. it's meant to serve as an acclimatization and growth acceleration chamber.

1) I want the palms to be exposed to similar overnight temperatures as in normal outdoors settings here, I only want to raise the daytime temperature by a significant amount to accelerate growth. The idea is that I do not want to baby along a palm that can't handle cool to cold nights. If the palm is not suitable for our climate, then I want to know early on. For small seedlings I plan on using bottom heat anyway. The single walled polycarbonate seems to provide little insulation, apparently the night time temp inside is only +3F to +5F max.

2) I would like the maximum possible natural radiation exposure. The single walled panels are 100% transparent and provide no light diffusion whatsoever.

What do you think? Good idea? Bad idea?

[_Keith]

I am putting up a greenhouse, and the one that I ended up getting for christmas is an inexpensive single walled polycarbonate greenhouse. At first, I hesitated, wondering if I should make the labor investment in building it, but after some consideration, I do see some upside given what I am trying to grow. I wanted to get people's input on this.

The greenhouse is not meant to create a special environment where I can grow palms that are otherwise marginal. it's meant to serve as an acclimatization and growth acceleration chamber.

1) I want the palms to be exposed to similar overnight temperatures as in normal outdoors settings here, I only want to raise the daytime temperature by a significant amount to accelerate growth. The idea is that I do not want to baby along a palm that can't handle cool to cold nights. If the palm is not suitable for our climate, then I want to know early on. For small seedlings I plan on using bottom heat anyway. The single walled polycarbonate seems to provide little insulation, apparently the night time temp inside is only +3F to +5F max.

2) I would like the maximum possible natural radiation exposure. The single walled panels are 100% transparent and provide no light diffusion whatsoever.

What do you think? Good idea? Bad idea?

Great place to start vegetables, too, if you are into such things. Makes a great big coldframe.

[Dypsisdean]

A cold frame (which is what you have) is what I (when I lived in SoCal) and many other growers have used for a long time - based on the strategy you mentioned. It accelerates the growth substantially, while still allowing acclimation to colder night time temps. Two years in a cold frame and your small palms will be 3 times larger than if you had planted them outside, and accustomed to the chilly nights.

However, I used a 40% shade on my roof to protect the smaller seedlings. A few sides still let in tons of sun, and I protected those sides a little as well. What I think you will find, depending on how much direct sun yours will get is that you will need to pay attention to temps in summertime - as without any diffusion, you may have problems. They make special paint for that purpose, or use shade cloth as I mentioned, so you can fine tune things a little easier.

But you will be surprised how much hotter it will get in there. And in summer, you can easily fry everything if you don't have adequate ventilation and/or some diffusion/shade. Mine was easily 15 degrees hotter inside most days, and it was only visqueen, and not even sealed all around.

But in short - I found it indispensable for giving those marginal palms a chance at surviving that first winter.

[Ben in Norcal]

I have just done the same, Axel, set it up in fall. I just got a basic little single poly Palram thing. I have found with the winter we are having (every day since early December near 70 it seems) that it is essential to open the greenhouse up during the day. If I don't, temperatures in the greenhouse are easily over 110 degrees. I have just ordered the automatic vent opener which I should have got with the kit in the first place. I underestimated the efficacy of this thing, I guess.

[Phoenikakias]

I never close windows in mine, even during the coldest winter nights

Edited January 5, 2014 by Phoenikakias

[daxin]

Forced air circulation from an oscillating fan is quite helpful in promoting robust growth and discouraging spider mite infestation. Plants enjoy a nice breeze as much as people do. Another tip is to lay a large piece of synthetic outdoor rug on the floor and to soak it with water in the morning. The extended evaporation will keep the relative humidity up all day inside your greenhouse, which in my opinion is more important than cooling during the warmest part of the day.

[Phoenikakias]

I use passive air circulation in that I have left openings at ground level about the one third of the surface of windows, which remain always open. Some bowls filled with water inside the frame provide needed air moisture. Sprinkler system provides watering, refilling of the water bowls plus some browsing of plants. A heated pad with thermostat and a bathroom heater with incorported thermostat also is all I use for the case of a freeze. Shelves on different heights may be used for palms with different warmth requirements. A southerly exposure is also essential (for the passive heat during winter mostly) but imo also some strategical depth towards North is also useful for stressed palms, which need provisorily cooler temps and less sun during summer (if a plant has damaged root system an exposure to high temps and full sun in summer would mean almost certain death because water uptake is insufficient and the more water you provide the faster still healthy roots will rot!). Only drawback with sprinklers and timer is that I can not control individual needs of every single plant, but with pumice also this problem can be solved easily.

Edited January 6, 2014 by Phoenikakias