A tomato plant covered in flowers that drop without making fruit is usually being told to stop by the temperature - and specifically by the night temperature, which is why the shade cloth everyone reaches for does nothing.
Midsummer, and the tomato plant looks magnificent. It is big, it is green, it is covered in yellow flowers - and every one of those flowers turns pale, loosens, and falls off without leaving anything behind. No fruit. Weeks of it.
This is the most misdiagnosed problem in a vegetable garden, because a healthy-looking plant that won't fruit invites you to go looking for something you did wrong. Usually you didn't. The plant is being shut down by the weather, and the specific number that shuts it down is not the one you are watching.
What is actually happening
Well establishedTomato fruit set fails when night temperatures persistently exceed ~21C (70F); high day temperatures (>29-32C) compound it.
costly if ignored → warn
Mechanism: Sustained high day (>29-32C / 85-90F) and night (>21C / 70F) temperatures make pollen non-viable ("tacky") and impair its release; flowers go unfertilized within their ~50-hour window and abscise.
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
Univ. of Missouri IPM, 'Understanding Tomato Fruit Set' (Missouri Produce Growers Bulletin), ipm.missouri.edu/MPG/2013/4/Understanding-Tomato-Fruit-Set (read 2026-07-11): 'When daytime temperatures exceed 85 degrees F or nighttime temperatures exceed 70 degrees F, pollination suffers due to pollen becoming "tacky" and non-viable.'
UMD Extension (J. Brust), 'Expect Poor Fruit Set in Tomatoes This Week', extension.umd.edu/resource/expect-poor-fruit-set-tomatoes-week (read 2026-07-11): 'Daytime highs of 90° F and above and nighttime lows only getting down to 70° F ... will cause blossom drop and fruit abortion in tomatoes.'
remedy
Wait it out — fruit set resumes on its own once nights cool, and the plants make up the gap. Do not reach for shade cloth: it cools the day, and this failure is driven by the night temperature, which Missouri IPM says shading will not touch. If hot nights are normal where you garden, buy a heat-set cultivar next season.
Read the full rule → · open in the planner ↗
Tomato pollen is temperature-sensitive in a way that is easy to miss. Held too hot for too long it goes, in the trade's own word, tacky - it stops being viable and it stops being released cleanly from the anther. A tomato flower is only receptive for roughly two days. If the pollen doesn't move and land in that window, the flower is never fertilized, and an unfertilized flower is dead weight the plant declines to carry: it abscises, which is the botanical term for the plant cutting the flower loose on purpose. That is the yellowing and the drop you're watching. Nothing has attacked the plant. The plant made a decision.
Two thresholds matter, and they compound. Days above about 29–32°C85–90°F hurt. Nights that stay above about 21°C70°F hurt more, and are the harder one to escape - a hot day at least ends.
Why the shade cloth doesn't work
Here is the part worth the whole guide. When it is 35°C95°F out and the flowers are dropping, the instinct is to shade the plant, and every garden centre will happily sell you the fabric to do it.
It will not fix this.
Shade lowers the daytime temperature. The failure this rule fires on is driven by the night temperature, and nothing you drape over a plant at noon changes how warm the air is at 3am. The extension service that supplies the 29°C/21°C85°F/70°F thresholds offers shade for the day and then withdraws it for the night in the same breath - shading, it says plainly, will not affect the night-time temperatures that are the thing reducing your fruit set.
This is unusual for a rule in this corpus: the remedy names a wrong move rather than a right one. It is here because the wrong move is the one you were about to make, it costs money, it costs an afternoon, and when it doesn't work you will conclude the plant is diseased and start treating it for something it doesn't have.
What does work
Three things, in descending order of how much they matter.
- Wait. This is genuinely the main answer, and it is the answer nobody wants. Fruit set resumes by itself once the nights come down, and tomato plants are good at making up the gap - the flowers you lost in the hot fortnight get replaced by the ones set afterwards. A plant that dropped everything in late July is very often loaded in September. Don't rip it out mid-heatwave.
- Keep the water even. Heat won't be fixed by watering, but a plant swinging between bone-dry and flooded in hot weather will hand you a second, separate problem on top of the first - the sunken black patches of blossom-end rot, which is a water-delivery failure and not a soil deficiency. The how to water guide covers the deep, steady rhythm that avoids it.
- Buy a heat-set cultivar next season. If hot nights are simply what summer is where you garden, this is not a bad year - it is your climate, and it will happen again. Some tomato varieties are bred specifically to set fruit through it; look for "heat-set" or "heat-tolerant" on the packet or the plant tag. That is a decision for the seed order, not for this week.
Rule out the other two "no fruit" problems first
"My plant flowers and I get no fruit" describes three completely different failures, and the fix for each is useless against the other two. Before you settle on heat, check which one you actually have.
Is it a tomato, or is it a squash? This matters more than it sounds. The corpus records tomato's pollination as self, buzz-assisted: a tomato flower carries both parts, fertilizes itself, and only needs the pollen shaken loose - which wind, or a passing bumblebee, normally does. A squash or cucumber is the opposite case entirely; it carries male and female flowers separately and an insect has to physically ferry pollen between them:
Well establishedAn insect-pollinated crop depends on an insect to move pollen between its flowers; no arrangement of plants substitutes for one.
suboptimal if ignored → advise
Mechanism: A monoecious cucurbit bears pollen and ovules in separate flowers, so fertilization requires a vector to carry pollen between them - neither wind nor self-fertility applies. Ovules that are not fertilized do not develop, and the fruit aborts or forms misshapen.
Evidence: confirmed against 4 sources in the research-based literature.
the 4 sources
Clemson HGIC 1321, 'Summer Squash', hgic.clemson.edu/factsheet/summer-squash (fetched in-container 2026-08-01, READ AND CONFIRMED BY THE MAINTAINER 2026-08-01): 'Squash have separate male and female flowers on the same plant, and pollen must be transferred from the male flowers to the female flowers by bees.' And the consequence, stated categorically: 'Poor pollination will result in no fruit formation or either poorly formed fruit.' Note the page discusses blossom-end rot SEPARATELY as a calcium disorder, so the malformation claim here is not that confusion. [read]
UMN Extension, 'Growing summer squash and zucchini in home gardens', extension.umn.edu/vegetables/growing-summer-squash-and-zucchini (fetched in-container 2026-08-01, READ AND CONFIRMED BY THE MAINTAINER 2026-08-01): 'An insect must move the pollen from the male flowers to the female flowers. Bees are common squash pollinators.' And on the failure: 'Poor fruit set could be due to not enough pollination.' THE SAME PAGE IS WHY THIS RULE REFUSES TO DIAGNOSE: 'Cold, rainy or cloudy weather can reduce pollination', and 'It is also common that the first flush of fruit isn't adequately pollinated; time often solves this issue as bees find the planting.' [read]
UMN Extension IPM, N. Hoidal, 'Limited fruit set and fruit abortion in winter squash and pumpkins', 2019-08-30, blog-fruit-vegetable-ipm.extension.umn.edu (fetched in-container 2026-08-01, READ AND CONFIRMED BY THE MAINTAINER 2026-08-01): 'Pumpkins and squash are dependent upon insect pollination.' On which insects, which is why the remedy speaks of forage rather than of honeybees: 'Bumblebees and squash bees (Peponapis pruinosa) are the best pollinators of pumpkins since they forage in the morning.' [read]
UMD Extension, 'Vegetable Plant Pollination in a Changing Climate', extension.umd.edu/resource/vegetable-plant-pollination-changing-climate (fetched in-container 2026-08-01, READ AND CONFIRMED BY THE MAINTAINER 2026-08-01): 'Summer squash flowers require insect pollination and are only open in the morning', and on incomplete pollination, 'Fruits may also be small, malformed, and have few seeds.' WHAT THIS SOURCE DOES NOT BUY, recorded so the rule cannot grow into it: its recommendation is the unquantified 'Plant a variety of flowering plants in or around your vegetable garden to attract pollinators'. That is another rule here's territory, held there at a weaker confidence than this rule. NOT ONE OF THESE FOUR SOURCES SAYS A GARDEN WITHOUT FORAGE SETS LESS FRUIT, which is precisely why the claim above is the REQUIREMENT and the forage gap is only the trigger. [read]
remedy
Nothing here can guarantee insects, and their absence cannot be diagnosed from a plant list. What you can change is whether anything in the garden is in flower while the crop is. Plants that feed insects near a fruiting crop are a reasonably supported suggestion, not a proven fix.
Read the full rule → · open in the planner ↗
So "there are no bees this year" is a real diagnosis for your squash and a red herring for your tomatoes. If both are sulking, they are sulking for different reasons. The pollination guide covers the insect-vector side.
Is the fruit setting and then going wrong? If you are getting fruit but it develops a leathery, sunken black patch on the bottom, that is not a fruit-set failure at all - it is blossom-end rot, a different mechanism with a different fix, and the eggshells and Epsom salts you'll be told to use are aimed at the wrong problem.
Is it just early? A young plant, or one that went out at the very start of the season, may not be in its fruiting window yet. The planting calendar guide covers reading your own dates rather than the packet's generic ones.
The short version
Flowers dropping in a heatwave is not a disease, not a deficiency, and not a pollinator shortage. It is a plant declining to set fruit with pollen the temperature has spoiled, and the temperature that did it was probably the overnight low rather than the afternoon high. Water evenly so you don't earn a second problem, leave the shade cloth on the shelf, and let the nights come down.
