Why Are My Tomato Flowers Falling Off?

There are few more disheartening sights than a tomato plant covered in flowers that, one by one, yellow at the stalk and drop to the ground without ever setting a single fruit. You did everything right to get those blossoms, and the plant is simply letting them go. This is called blossom drop, and it is almost always the plant's reaction to stress at the critical moment of pollination. The causes are specific, and most are fixable. Let me explain.

Temperature is the number one cause

Tomato flowers are fussy about temperature, more than almost anything else. They pollinate and set fruit properly only within a fairly narrow band. When night temperatures stay below about 55 degrees Fahrenheit, or daytime temperatures climb above roughly 90 degrees, the flowers fail to pollinate and the plant aborts them. Pollen becomes unviable or sticky in extreme heat and simply does not work in the cold. This is why blossom drop is so common during early-season cold snaps and again during midsummer heatwaves — the two ends of the temperature problem.

There is not much you can do about the weather, but you can soften it: shade cloth during a brutal heatwave, and protecting early plants from cold nights both help. Most importantly, know that when temperatures return to the comfortable 60s and 70s at night, fruit set usually resumes on its own. Patience through an extreme spell is often the whole answer.

Too much nitrogen

If your plant is enormous, lush and dark green but dropping its flowers, suspect over-feeding with nitrogen. A plant flooded with nitrogen pours its energy into leaves and stems and treats flowering as an afterthought, readily shedding blossoms. Cut back on high-nitrogen feed and switch to a feed higher in phosphorus and potassium, which support flowering and fruiting. The plant will start holding its flowers and setting fruit.

Water stress and humidity

Inconsistent watering is another trigger. A plant that swings between drought-stressed and waterlogged will shed flowers as a survival response, dropping the parts it cannot afford to support. Keep watering deep and steady, with mulch to even out soil moisture. Humidity matters too: pollen needs the right moisture level to transfer. In very dry air it does not stick to the flower's pistil, while in very humid, wet conditions it clumps and cannot move. Both extremes reduce fruit set.

Help with pollination

Tomatoes are self-pollinating — each flower has the parts it needs — but the pollen still has to physically move within the flower, usually shaken loose by wind or buzzing bees. In a sheltered spot, a greenhouse, or a still patch with few pollinators, that movement may not happen. You can do it yourself: gently shake the flower trusses every day or two, or tap the stems, or even use an electric toothbrush against the truss to vibrate the pollen loose. It feels silly, but it genuinely lifts fruit set when natural movement is lacking.

The bottom line

Blossom drop is the plant protecting itself when conditions are not right for fruiting. Check the temperatures first, since extremes are the usual cause and usually pass. Then make sure you are not over-feeding nitrogen, keep watering steady, and give pollination a helping hand if your plants are sheltered. Sort those out and your flowers will start turning into fruit.