Why Blossoms Drop on Tomato Plants
Blossom Drop in tomatoes can be caused by several things: extremes in temperature, nitrogen imbalance, humidity, or lack of pollination or water. The most frequent cause is the temperature. Tomatoes do best with daytime temps ranging between 70 and 85 F and night temps between 55 and 70. Anything outside that range for extended periods can cause the plants to abort the flowers and move into survival mode.
During weather extremes, there are often no insect pollinators in the garden, so along with use of Blossom Set Spray you might try hand-shaking the flower to carry the pollen from anthers to stigma to ensure you’re getting pollination. You could also plant some bee-attracting plants near your tomatoes to help attract more bees.
Some other guidelines to follow might be backing off the fertilization of the plants; if your soil is rich in humus you might be overfertilizing. Just apply a balanced fertilizer, like a Tomato-tone, when you plant and again when the plants begin to form fruit.
If the humidity in your area is higher than 70% or lower than 40% then it interferes with the pollen’s ability to stick to the stigma. If you have low humidity, try misting the foliage during the day. If you have consistently higher humidity then you would want to look for varieties that are not bothered by humidity. Otherwise water deeply only once a week during any dry spells–remember that frequent, shallow watering only weakens plants.
One other possibility is that your tomato plants may have just gone crazy and created too many blossoms. With that competition it has to drop some of the blooms to balance out what it can support with the food supply.