Why Are My Tomatoes Flowering but Not Fruiting? Causes and Fixes

Your tomato plants look fantastic — lush, green, covered in cheerful yellow flowers. And then… nothing. The flowers open, linger, and drop off, leaving bare trusses where tomatoes should be swelling. It is one of the most frustrating sights in vegetable growing, because the plant is clearly trying. Flowering without fruiting has a name — blossom drop — and it almost always comes down to conditions, not a sick plant. Here is how to diagnose it and get your trusses setting again.

First, the botany in one paragraph. Tomato flowers are “perfect”: each contains both male and female parts and can self-pollinate. But the pollen has to physically move from anther to stigma, which happens via vibration — wind, or ideally a bumblebee’s buzz-pollination, which shakes pollen loose far more effectively than honeybees manage. Anything that interferes with pollen viability or that vibration means unfertilised flowers, and unfertilised flowers drop. Your job is to find the interference.

Cause 1: temperature (the big one)

Tomatoes are fussy about temperature at pollination time. Daytime highs above about 32°C make pollen sterile; nights below 13°C or above 24°C interfere with fertilisation. In a British context, this means two classic scenarios: a cold May/June where nights dip and flowers drop, and a July heatwave where a greenhouse or polytunnel soars past 32°C and every new flower aborts. Cherry tomatoes tolerate a wider range than big beefsteaks, which is one reason beginners do better with cherries.

The fix is environmental. In heat: ventilate aggressively — vents and doors wide open from morning, shade netting on south-facing glass, and damp down paths to cool the air. In cold: keep greenhouse doors closed at night, consider fleece over outdoor plants, and be patient — as this UK-focused guide to tomatoes not setting fruit notes, in our short British summer the early trusses are the ones that ripen before September, so protecting them matters disproportionately. Fruit set usually resumes within a fortnight once temperatures moderate.

Cause 2: still air (the greenhouse trap)

Outdoor tomatoes get wind; greenhouse tomatoes often get stagnant air — and without vibration, self-pollination fails even when temperatures are perfect. This is the single most common cause of flowering-without-fruiting in greenhouses and conservatories. The fix is gloriously low-tech: tap each truss gently every morning, or give the plant’s stem a shake. Some growers use an electric toothbrush held against the truss for a few seconds — it mimics buzz-pollination beautifully. Iowa State’s extension service confirms that unfavourable conditions interfering with pollination are the primary reason for blossom drop, and mechanical shaking is the standard remedy where bees cannot reach.

Open vents and doors serve double duty here: airflow for pollination plus temperature control. If you grow in a sealed conservatory, a small oscillating fan on a timer transforms fruit set.

Cause 3: watering stress

Both drought and waterlogging cause flower drop. Tomatoes want deep, consistent watering — irregular cycles (flood, drought, flood) stress the plant into aborting flowers it cannot support. Water at the base, deeply, and mulch to hold moisture steady. Inconsistent watering also causes blossom end rot later, so this fix pays twice. Containers dry out far faster than beds — in hot weather, large pots may need watering twice daily.

Cause 4: feeding mistakes

Too much nitrogen grows magnificent leafy plants with no interest in fruiting — the classic “all leaves, no tomatoes” outcome from overfeeding with general fertiliser or fresh manure. Once flowers appear, switch to a high-potash tomato feed and go easy: little and often beats occasional drenchings. Underfeeding can also cause drop, but in British gardens overfeeding is the more common sin.

Cause 5: light and overcrowding

Tomatoes need 6+ hours of direct sun to fruit well. Plants crammed together in a shady corner will flower hopefully and set nothing. Space plants for airflow and light, prune indoor plants to a single leader (removing side shoots), and do not let a jungle develop — good air circulation also prevents blight, the other great tomato heartbreak.

Cause 6: the plant is simply too young (or too old)

Sometimes the answer is patience. The first truss on a young plant often drops a few flowers while the plant is still putting energy into roots and foliage — completely normal, and later trusses set fine. At the other end of the season, September flowers in a fading British summer often fail simply because light levels and temperatures are falling; the plant knows winter is coming even if you are in denial. Neither needs fixing, just realistic expectations about which trusses will actually ripen.

The diagnostic walkthrough

Work through this order: 1) Are nights below 13°C or days above 32°C? → temperature. 2) Is the plant somewhere still — greenhouse, conservatory, sheltered corner? → tap the trusses daily. 3) Is watering erratic or the compost swinging between soggy and bone-dry? → stabilise. 4) Have you been feeding heavily with nitrogen-rich feed? → switch to potash, ease off. 5) Is it dark or overcrowded? → light and space. 6) Is it the first truss or late September? → patience. In most cases the answer is one of the first two, and the fix works within two weeks.

And keep perspective: a plant that flowers prolifically is a healthy plant with a conditions problem, which is the easiest kind of problem to have. Sort the air and the temperature and the fruit follows — usually just in time. While you are at it, the rest of the plot deserves attention too: making a small garden look bigger helps with the layout that gives tomatoes the light they need, and the best lawn feed for UK grass covers the other half of the garden.

The bottom line

Tomatoes flower but do not fruit because of blossom drop — almost always temperature stress, still air preventing pollination, erratic watering, or excess nitrogen. Tap the trusses daily, ventilate and shade in heat, protect from cold nights, water consistently, and feed potash once flowering. Do that and the flowers that were dropping will start holding within a fortnight — and in a British summer, a fortnight is everything.

Frequently Asked Questions

Why do tomato flowers fall off without forming fruit?

Unpollinated flowers drop — the plant aborts what it cannot fertilise. The usual culprits are temperatures above 32°C or nights below 13°C (sterile or inviable pollen), still air with no vibration to release pollen, or water/feed stress.

Do tomatoes need bees to pollinate?

Not strictly — tomato flowers self-pollinate with vibration from wind or shaking. But bumblebees’ buzz-pollination is far more effective, so encouraging bees and tapping trusses daily both improve fruit set.

Should I remove flowers from tomato plants?

No — each flower is a potential tomato. The problem is never too many flowers; it is failed pollination. Fix the conditions (temperature, airflow, water, feed) rather than removing flowers.

How do you hand-pollinate tomatoes?

Tap or shake each flower truss gently every morning, or hold an electric toothbrush against the truss for a few seconds to mimic bee vibration. Morning is best, when pollen is fresh and humidity moderate.

What temperature do tomatoes need to set fruit?

Ideally days of 21–29°C and nights of 13–21°C. Above 32°C pollen goes sterile; below 13°C at night fertilisation fails. Cherry varieties tolerate a wider range than large-fruited types.