Stop blossoms from dropping off tomatoes

Question from Holt:
Wondering why my tomato plants keep dropping their blooms?

Answer from Pat:
Tomatoes often drop blossoms early in the season. (This problem and solutions are discussed on page 171 of my book in the chapter for April, which is when this problem usually happens.) There are several reasons and more than one solution.

If tomato roots dry out completely, the blossoms will always fall off. The solution is to water deeply and infrequently rather than shallowly and often so the roots go deeply into the ground.

Another reason blossoms can fall off is lack of pollination. The flowers of tomatoes are called “perfect flowers” because they contain both male and female parts. Thus they are self-pollinating and the wind is what pollinates them. Bees may help but tomatoes don’t need bees. All that is necessary for a tomato to be pollinated is for the blossoms to be shaken enough by the wind so that the dry pollen can travel the short distance from the male anthers onto the sticky female stigma. If there is no wind and no bees or if the pollen is wet, the flowers may not get pollinated. This can happen if you are growing tomatoes in a very sheltered spot, such as a walled patio or in a greenhouse. If this sounds like your situation, be sure to shake the plants in the middle of the day when the pollen is dry. Simply go out there daily around noon and hit the stakes with a hammer. This will make your neighbors, if they see you, quite sure you have gone completely coo-coo but it will also vibrate the flowers enough to pollinate them and then you should get fruit.

However there is another reason that could be cause the blossoms to fall off may be that night temperatures have been too cold and/or the days have been too hot. If nighttime temperatures fall lower than 55 degrees Fahrenheit or higher (at night) than 75 degrees Fahrenheit or if the daytime temperatures are higher than 105 degrees Fahrenheit, the blossoms of tomatoes will fall off. (Desert dwellers should not try to grow tomatoes in the summer but may be able to grow them in fall, winter, and spring.)

If you live in a coastal zone and cold nighttime temperatures have been causing blossoms to fall off, then your solution is two-fold. Next year plant and grow early varieties early in the season. (‘Early Girl Improved’ is a good one and it is widely available in nurseries. If you prefer growing heirlooms look for the ones that say “cold resistant” or “early” on the label.) Additionally, I have had good luck in my own home garden by spraying the flowers with “Tomato Blossom Set Spray“. This is a hormone that comes in a spray bottle and is available in most nurseries. Follow the directions exactly. A short burst of spray a but ten inches from each flower is all that is necessary, and do not use the spray on your plants more than three times at intervals of ten days. (On the day you spray, put it on your calendar so you will remember when to spray the next time, ten days hence, and then once more ten days after that.)

Blossoms falling off tomatoes early in the season is a frequent problem and in my garden was always caused by cold night temperatures. Thus, I made a habit of purchasing and using blossom-set-spray every year. It worked well for me, but it is a hormone and is age-dated. It only lasts for one year. If one little container is too much, share it with a friend.