|Cutting back tomatoes in the hoophouse in July and August|
A. You don’t have to cut them back. They will begin to produce again as the temperatures cool this fall. However, if they have gotten too large or you want to reinvigorate them then you can cut them back. In our hot desert tomatoes stop producing when temperatures climb over the mid 90's or so. The ones that have set will continue to develp and ripen but no new fruit will set until cool weather sets in.
Whatever you use if you cut them back make sure it is clean and sterilized. You can cut back about 1/3 plant just above some side branches. Cutting the plants back will cause them to begin to grow vigorously as they tried to reestablish their tops to the existing root system. Do not cut them back to stems only or they most likely will just die.
If there is fruit still on the vine that you want to harvest and cutting the vine means removing the fruit than you might wait until after you finish harvesting. Then go ahead and cut.
Once you have trimmed the plant back then lightly apply some foliar fertilizers that focus on fruit production. Do this in the early morning hours. Apply this fertilizer in the early morning hours while it is still cooler and the sunlight is not so intense. This would mean a fertilizer high in the middle number or phosphorus and lower on nitrogen.
You want to stimulate some new growth but you want the nitrogen in the fertilizer to begin to fizzle out in a couple of weeks as daytime high temperatures cool into the lower nineties. I’m guessing that this will be toward the end of September but I am no weatherman.
You can apply a fertilizer to the soil but these generally last too long and can cause your tomatoes to grow excessively before they bloom again. Foliar fertilizers are usually short lived and you will get flowers sooner after an application. Try mixing it at half the label rate.
Whenever you are growing vegetables you should be applying light applications of fertilizer whenever you are harvesting. You are taking away from the plant so you need to give something back to it to help it recover from harvesting. I hope this helps.