Tomatoes Not Setting Fruit

tomato plant flowering

When it gets too hot the tomato flowers drop off without setting fruit.

Dag-nabbit, snarl, growl, argh, sniff…  It’s the middle of summer.  It’s supposed to be the peak of the growing season.  Why are the tomatoes not setting fruit?  What’s going on here?

As gardeners we go to great lengths to have fresh home grown tomatoes during the summer.  We pour over a half a dozen seed catalogs in winter trying to puzzle out from hundreds of descriptions which tomato will be the most prolific, the sweetest and the splooshiest (not the firmest, not the juiciest – the splooshiest).  Or we spend hours combing garden centers or farmer’s markets looking for the healthiest looking plants of our all-time favorite tomato varieties.  We plant, we stake, we water, we fertilize, and we wait.  Then our plants start flowering… and then… NOTHING!

Now that summer is officially here I feel obligated to make good on my promise to my husband to deliver fresh salsa. After all, it’s like a hundred degrees outside and the less often we have to use the oven the better.  But, there is a bit of a catch-22 here.  Tomatoes don’t set fruit once daytime temperatures go over and stay above ninety degrees.  Nor when nighttime low temperatures don’t get down into at least the lower seventies. Does that mean no salsa for my sweetie?

When extreme heat kicks in, tomato plants become more likely to drop their blossoms, than to set fruit.  The pollen inside the flower becomes sticky and unviable.  Besides, bees and other pollinators aren’t as active during the hottest part of the year and aren’t busy pollinating.

But all hope is not lost.  We can take a few measures to combat the summer stress and get the tomatoes fruiting.

First thing we can do – and this takes some extra planning – is select varieties that are tolerant of high temperatures.  Varieties like Sioux, Heatwave II, Nineveh, and Cherokee Purple all do well in high heat and the humidity that goes with it.

We can also plant flowers (ones with the stuff pollinators love).  Marigolds are well known for keeping small flies away, but they also attract some beneficials.  Having flowers may entice the right bugs to pollinate before the flower’s pollen becomes unviable.

Watering more often can also help keep our plants from getting stressed out by the heat.  Usually tomatoes only need about an inch of water each week, but when the heat is on, two or three inches of water is closer to what the plants need.  And of course don’t forget to keep plants fertilized and mulched…

If all else fails and still you find the tomatoes not setting fruit, it’s time to bring in the big guns!  Shade cloth and row cover (like Reemay) may be able to keep the plants just cool enough to ensure your tomato plants set fruit.  But that puts us in another catch-22!  If the tomato plants are covered to cool them off, they can’t get pollenated, either by the wind or by the bees!  Well, now it’s up to us.  Shaking the plant lightly may be enough to move the pollen around, failing that a cotton swab.  Just insert the same end of the swab into different flowers.

And voila, the tomatoes are finally setting fruit.  And it’s time enjoy some salsa with my sweetie!