Over-fertilizing gardens will often affect tomatoes and other crops.
Are your vegetables blooming…but no fruit?
K-State horticulture expert explains reasons, offers solutions
July 1, 2021
MANHATTAN, Kan. – For Kansas gardeners, watching vegetables bloom but not set fruit can be very frustrating.
Yet, for various reasons, that often happens this is the time of year, says Kansas State University horticulture expert Ward Upham.
“There are several possible reasons,” he said. “One condition that can affect several species is over-fertilization.”
Upham said that too much nitrogen in the soil causes the plant to emphasize vegetative growth, often to the detriment of fruit production. Over-fertilization can lead to a delay in flower production and a decrease in fruit set among the flowers that do produce.
“This is especially true of tomatoes,” Upham said. “Over-fertilized tomatoes will produce a large, apparently healthy plant with no flowers, or flowers that don’t set fruit.”
Tomatoes, a popular choice of many gardeners, also won’t set fruit if the night-time temperature falls below 50 degrees F, which leads to sparse pollen production, according to Upham.
“They also won’t set when night-time temperatures are above 75 degree and daytime temperatures are above 95 degrees with hot, dry winds,” he said. “Under such conditions, fertilization is not completed and no fruit develops. However, cherry tomatoes may be more forgiving of high temperatures than the larger slicers and will often set fruit in the heat.”
Upham said that many other crops – including squash, cucumbers, watermelon and muskmelon – can experience other problems.
“First, the early flowers on these plants are usually all male; the production of male and female flowers becomes more balanced as time passes,” he said. “You can easily tell the difference between the two because only the female flower has a tiny fruit behind the blossom.”
Upham said that if gardeners see both male and female flowers, have not fertilized, but still have a problem, it could be that the garden does not have enough pollinators.
“Look for the presence of bees visiting the plants,” Upham said. “If you don’t see any, try hand-pollinating several flowers. Use a painter’s brush to transfer pollen from the anther of the male flower to the stigma of the female flower. If you get fruit on any of those flowers you pollinated, you need more pollinators.”
Upham also cautioned against the over-use of insecticides, which can kill pollinators. He advises spraying near dusk when flowers have closed.
Upham and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes. The newsletter is available to view online or can be delivered by email each week.
Interested persons can also send their garden- and yard-related questions to Upham at wupham@ksu.edu, or contact your local K-State Research and Extension office.
FAQs
Heat stress, over-fertilization and a lack of pollinators are among the reasons that vegetables may bloom – but not produce fruit – during the summer months.
Why are my vegetables flowering but not producing fruit? ›
Besides a lack of pollen transfer from male to female flowers, there are other reasons that vegetables sometimes produce flowers but not fruit. In tomatoes, nighttime temperatures below 55 degrees F or above 75 degrees F can interfere with pollination. Daytime temperatures above 90 degrees F can cause blossoms to drop.
Why are my tomatoes flowering but not fruiting? ›
Insufficient sunlight
The lack of adequate sunlight can result in the lack of fruiting. A fully grown tomato plant requires six to eight hours of daily sunlight to produce flowers and then fruits. Without proper sunlight, the tomato plant will have leggy and spindly growth and little or no fruits.
Why aren't my vegetables fruiting? ›
If your plants produce blooms but they do not develop fruit or the fruit that do form are misshapen, then you may have low or incomplete pollination. Many fruiting crops require cross-pollination to set fruit. This is especially important in cucurbit crops like squash, cucumbers, melons, and pumpkins.
Why does my squash have flowers but no fruit? ›
Based on your description, I'd say the reason your plants aren't setting fruit is because they are not being pollinated. This can be caused by a lack of pollinators or simply because the pollinators aren't moving between flowers and transferring the pollen.
How do I get my plants to produce fruit? ›
Your plant might not be producing fruit because it's hungry. Fertilizing can give your plant the boost it needs to start fruiting. Make sure to choose a fertilizer that is made for garden plants or fruiting plants. Fertilize according to directions on the bottle.
How do I get my tomato plants to produce fruit? ›
Tomatoes “set” fruit best when daytime temperatures are in the 70- to 85-degree range and nights are between 55 and 70 degrees. They do this by transferring pollen from the stamens of male flower parts to the pistils of female ones. That fertilizes the pistils and triggers the growth of fruit.
What do you do when tomato plants don't produce fruit? ›
If you're faced with tomato plants not setting fruit, the best thing to do is to keep the plants healthy and fertilized with plant food, such as Miracle-Gro® Shake 'n Feed® Tomato, Fruit & Vegetable Plant Food. The plants will start to produce again when the weather becomes favorable.
How do you encourage fruiting? ›
Regularly pruned trees are much more apt to producing quality fruit. Fruiting buds tend to form on limbs that have adequate air circulation and light infiltration, which is your goal when pruning. Learn about pruning tips and more in our article, Successful Tree Pruning.
Why would a plant not produce fruit? ›
The absence of pollinators or low numbers of female flowers can result in fewer fruits produced. Poor Pollination: This is one of the most common causes of no fruit. Some plants cannot pollinate themselves. They require a plant of the same species, but a different variety for cross-pollination and maximum fruit set.
Undoubtedly in the backyard situation the number one reason for failure of trees to bear fruit is improper tree vigor. Over vigorous trees expend all their energy in growing wood and do not produce flower buds. Typically, this occurs for two reasons: over-fertilization and over-pruning.
How do you encourage squash to fruit? ›
Encourage More Squash Flowers
Excess nitrogen will encourage lots of leafy growth at the expense of flowers. Either reduce the amount of nitrogen you are applying in your feed, or switch to a feed with a higher concentration of potassium, which should encourage more flowers and, hence, fruits.
Do you need two zucchini plants to get fruit? ›
That increases the odds of pollination. Other summer squashes and pumpkins will also pollinate zucchini. Keep in mind that zucchini are self-fertile, so you don't need multiple plants for pollination. But having more than one can improve fruit set.
How long does it take for squash to fruit after flowering? ›
Squash grow rapidly, especially in hot weather, and are usually ready to pick within 4 to 8 days after flowering. Although summer squash has both male and female flowers, only the female flowers produce fruits. Because the fruits are harvested when still immature, they bruise and scratch easily.
Why are my peppers flowering but no fruit? ›
Poor Pollination Can Cause Plants Flowering But Not Fruiting
Another potential reason your pepper plants aren't producing could be poor pollination. Pepper plants contain both male and female parts.
How to encourage fruit set? ›
Warm, dry conditions encourage fruit set, while extremes in temperature and soil moisture diminish it. Excessive rainfall and high winds are also disruptive. Excess growth vigor from training-trellis-spacing-pruning systems undersized for their sites or excess available nitrogen can diminish fruit set.
