Why are the flowers on my tomato plants dying off before developing?

by Marian
(Cancun, Mexico)

Q. I'm a newbie tomato grower (this year's my first attempt). I live in Cancun, so we've got average daytime temps of around 30 C (8 6F) and high humidity. My plants are in containers on our third floor terrace, and are planted in a mixture of a pre-prepared potting mix with a prepared goat manure mix.

Everything has been going fine, with the plants coming up nicely and flowers coming out, but they're not developing into fruit. I'm guessing that they´re not being pollinated as we don't get the necessary bees/birds up on the 3rd floor.

Any suggestions/tips would be greatly appreciated!

A. Congratulations on your first year of gardening and welcome to the gardening world!

As for your tomato plants ... two issues come to mind.

Watch the heat. First, your plants may be experiencing "blossom drop" - a healthy tomato plant flowers, its blossoms drop, and no fruit develops. Consistently high heat or stress causes blossom drop. Hot spells (days consistently about 90ºF and nights consistently above 75ºF) force the tomato plant to abandon fruit production and focus merely on surviving. Tomatoes’ optimum daytime temperature range for setting fruit is between 70º-85ºF. Try to plant seedlings earlier in the season so they can set fruit before heat sets in. Alternatively, choose varieties that take less time to mature (early season tomatoes), or varieties that are heat-tolerant. For now, do what you can to shade plants during the heat of the day. You can read more about blossom drop in tomatoes.

Encourage pollination. Even without birds or insects, you can help "pollinate" your tomato plants by gently shaking them once or twice a day after blossoms open up. Many gardeners have also had success in encouraging tomatoes to set when they apply tomato blossom set spray.

Good luck and happy gardening!
Your friends at Tomato Dirt