I don't know why you would need a greenhouse for kaki. They grow well in zones 5 and warmer. If you do put it in a greenhouse, you need a method for opening the green house during the warmer weather.

There are mechanical arms which open once the temperature exceeds a limit. They are purely passive (part of the mechanism expands thermally, and once that part exceeds a certain length, the arm is forced to extend fully), not very reliable because the tolerances are tight, and they can only drive small loads. Look for vent openers on google. Otherwise just buy an electrical vent opener with thermostat and electrically driven arm.

I am interested in this because I am considering making a large tunnel for persimmons, figs, and other Zone 8 fruits, influenced by Fruitnut. I can not see the advantage of a GH over a tunnel, specially since the plastic can be removed quickly. One layer buys you some 15F, but that is all that is needed to keep the plants alive. I would just need a couple vent openers.

Charlie,

You are very Optimistic if you plan on growing Kaki in zone 5 without a ideal microclimate and/or protection

The passive cooling systems aren't very effective because there isn't enough air movement. You need exhaust fans that exchange the air once every minute to hold temperature rise to 15F. To get more cooling an evaporative cooling system like mine is needed. I can hold inside temperature below outside if dew point is low. To do that you still need the one air exchange per minute from exhaust fans and a wet wall on the opposite side of GH.

My greenhouse, double layer poly inflated, offers almost no freeze protection unless heated. So there are no short cuts on either heating or cooling. Besides overheating and freezes one also needs chilling and proper temperatures and humidity to grow and ripen the chosen crop. One needs to understand how a greenhouse works and set it up to match the climate and crop objectives.

If the owner of the greenhouse in question is willing to make upgrades I would be glad to help set it up properly. Colorado is a great climate to grow almost anything in a greenhouse. But if the setup is wrong failure is close at hand.

The approach outlined above is for a full out greenhouse. For those crops that can be exposed to the weather during the frost free season, a high tunnel approach would be less expensive. But you still need control of the temperature during the rest of the year, 7-8 months in z5 CO. This might involve roll up sides and many other options. This approach would be harder to automate and just one missed freeze or over heating event can ruin the whole year.

Okay, I appreciate all the honesty. I will let the idea pass. I have ordered an NC-10 from Cliff England. I am supposing that I will not have to bother with any particular protection for Virginiana.

I am curios about the hybrids such as Nikita's Gift and Rosseyanka. Would either of these be hardy enough for zone 5 and still give fruit close to the fruit of a kaki? Catalog descriptions are always glowing. What is the real deal with these?

MG,

Rossyanka can handle temp of -20F just fine. I do not protect my Rossyanka at all.

Tony