Tomatoes Not Setting Fruit? This Weekend, They Might!
Lately, in several different threads, we've discussed the high temperatures and humidity and how they've kept many large-fruited tomatoes from setting tomatoes this year.
If your tomatoes have been affected, this weekend's lower temperatures will give your tomatoes at least at good chance of pollinating and setting fruit, especially on Sunday.
You can improve their chances in a couple of simple ways.
1) If your tomatoes are caged, trellised or staked, grasp the cage, trellis material or stake, and gently shake the plant. This can loosen up clumping pollen and cause it to move around in/on the flower and pollinate. This works best if you do it during cooler early morning temperatures, or cooler evening temperatures, especially shortly after sunrise or shortly before/after sunset. Doing this a couple of times a day really does help improve fruit set, especially on the occasional "cooler" day like we're going to have this weekend.
2.) If your temperatures are on the borderline of those that allow pollination--max. temp. of about 92 to 95 and min. temp. lower than 75 (but higher than 55), shaking alone may not be enough but you can improve the odds by "cooling" down the pollen and flowers with a brief spray of water from the hose during the hottest part of the day (or night). You don't want to hit the plant with such a hard stream of water that the flowers fall off, obviously, though! Do this at least twice daily when temperatures are right at the threshold of being "too hot" and it can cool the flowers just enough that they will set fruit.
3.) Some people use an electric toothbrush (I've never tried this one myself) to "vibrate" or "shake" the flowers to improved fruit set. If you are interested in trying this, there is a thread on this topic on the Tomato Forum that describes how it is done.
4.) Some tomato experts recommend that, on certain plants like Brandywine which is notorious for not setting fruit in hot weather, you emasculate the Brandywine flower and use a Q-tip to transfer pollen from a DIFFERENT variety to the Brandywine. You still will get Brandywine fruit from this fertilization, if it takes, but seed saved from THAT tomato could give you a cross-pollinated fruit if you plant that seed next year. If you want to know how to do this, do a search for "emasculate flower" on the Tomato Forum. One of the guys on the forum linked a video that shows how. Emasculating a flower and manually transferring pollen is one way that home gardeners/tomato hobbyists can do deliberate cross-pollination in an attempt to "breed" a tomato plant that is a cross of two or more different varieties.
You can use the above techniques to improve the odds of fruit set any time, but they are especially effective when we are having the occasional slightly cooler weekend.
I'll be shaking my cages and thumping my flowers this morning! Actually, I've been doing it all week, and it must be working--yesterday I noticed some brand new baby tomatoes on several large-fruited plants, like Brandywine Sudduth, True Black Brandywine and Jerry's German Giant last night. For new fruit to set when our highs have been in the upper 90s is amazing, almost miraculous.