Varieties that tolerate heat

rgvnewf(z5 NL,Canada)November 14, 2011

I'm looking for some suggestions. Where I live my growing season is not long enough or reliably warm enough to grow tomatoes outside, so I grow in a greenhouse. The problem is as a result I have to watch the temperature and make sure it does not get too hot inside the greenhouse. I keep the windows open and have a fan set up to circulate and cool the air, but sometimes the temps do get too hot. I am looking for suggestions for indeterminate varieties that do well and set fruit reliably in hot temperatures. I had several plants this year that did not set fruit (Aunt Gerties Gold, NAR, Pineapple) and I think it was because it was too hot when they were in bloom. I have some vents where insects can get in through and I give the plants a gently shake almost daily to encourage pollination, however some plants just did not set fruit.

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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

There is another discussion just down the page a bit titled "What varieties will continue to produce through hot weather?" that will give you the names of a few varieties - most have "Sun" in their name.

But assuming your plants bloomed but didn't set fruit and that you understand about the condition called Blossom Drop and what causes it then you know that no variety will "set fruit reliably in hot temperatures" above 95, especially with high humidity. And controlling humidity in the greenhouse can be as difficult as controlling the heat.

I assume you are using a shade cloth on your greenhouse during the hottest days? Have a misting system? Have a way to increase the air exchange rate substantially?

Based on my experiences with my greenhouse it is changes in the greenhouse than need to be made rather than the variety for really successful fruit set.

Good luck.


Here is a link that might be useful: Blossom Drop FAQ

    Bookmark   November 14, 2011 at 2:03PM
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You mentioned opening windows so it appears that you either have a glass partition greenhouse or have end wall windows. With the glass units you have options of spraying a light blocker onto the glass which should help. With a plastic film covered unit I think roll-up sides are a must to keep temps low unless you install an expensive ridge vent system. I ignore the end wall exhaust fans in mid summer and leave the sides rolled up day and night. Themperatures inside may still reach 100F but most varieties seem to handle that extreme. Heirloom varieties will be affected sooner than most hybrids and there are a few newer varieties that should set fruit at higher than normal temps (see 2012 Twilley seed catelog).

    Bookmark   November 20, 2011 at 7:14PM
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Opening up the greenhouse is a good idea to let in as much cool air as possible,I would also place some shade cloth over the greenhouse to reduce the direct sun to the plants during the hottest part of the day.The tomatoes should still produce fine.Good luck!

    Bookmark   November 20, 2011 at 9:19PM
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