How High Day And Nighttime Temperatures Affect Tomatoes

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By Jannie Vaught

Using the tomato due to its popularity and my personal keystone plant to evaluate the garden’s condition. Will extreme heat kill my tomatoes? Maybe not. Will heat especially nighttime temperature affect fruit set? Yes. Heat consistently above 90 and nights above 70 will greatly reduce the plant’s ability to flower and pollinate. There is a critical time when the first tomato flowers appear that they open and pollinate with the stigma. But if they cannot open and pollinate they will drop their flowers as unpollinated. And this is all heat.

Think location!!

Where did you plant them thinking we were having a somewhat normal spring and into summer growing season. There is a difference when the package says Direct Sun and Full Sun. Full sun is 6 hours per day, and Direct sun can be sun through a window. During extreme heat, tomatoes need some relief from the Full sun. Water at least twice each 12-hour period. Early morning and evening. Mulch with grass clippings or composted leaves under the plant to cool soil and put shade cloth over them. We are just at this point keeping them alive after all the effort we have put into them. When monsoon arrives and we get rain and relief they will try again.

I did go out this morning and do some pruning and found non-pollinated flowers, I clipped off as many under branches and succors as possible without making the plant bare. It needs all the leaves it has at this point for the transpiring of water through its leaves. and shade cloth is over them. I made compost tea last week and that did give them a boost the cherry and paste variety tomatoes are producing as are the Heritage and I’m finding they are slow to ripen and are lower on the stalk. Also, peppers and cucumbers are greatly slower than usual. but are full of flowers and the bees are active. Keep the soil as cool and damp as possible and keeping this intense scalding heat off the plant will help these stressed plants. A heat wave means: tomato blossoms won’t open, polling is destroyed, no new fruit will set until normal temperatures resume, leaves curl, and plants are simply trying to survive. Here we are almost at summer and at this point finishing and preserving as much as possible from this year’s garden will be an achievement.

There is always the late summer and fall garden which I find to be the most productive gardens. Start looking at the coming seasons and soil conditioning, compost, and the lovely cooling and cold weather veggies you can grow. It’s not always tomatoes and peppers. Start considering late squash, collard greens mustard, and kale. A cover crop is a great way to revitalize and replace the nitrogen in the soil by planting beans, peas, and clover as cover crops and then chopping and dropping them for composting direct.

We haven’t given up, as gardeners, we are always learning and adjusting.

Growing Green with Jannie