Are you seeing lots of flowers on your tomatoes but not enough red fruit? From lack of pollination to extreme heat, there are some reasons why this happens, but also most are addressable. See our article (with video demo) to find out how to get more tomatoes—and reap the fruit of your labors!
Lack of Pollination
While other fruiting vegetables like squash produce separate male and female flowers, tomatoes have flowers with both male and female parts. This means they’re self-fertile and can pollinate themselves. But while that’s technically the case, you’ll get much better fruit set if pollinating insects – and especially bumblebees – enter the mix.
Bumblebees ‘buzz pollinate’: Their wings flap up and down at a frequency that creates their famous low, audible buzz–and it’s this buzz that produces a vibration, so that when they visit a flower the pollen is shaken free from the male part to drift down onto the waiting female stigma. We want more bumblebees, so make sure they can get at the flowers!
*If you’re growing under cover, open up greenhouse or tunnel vents, windows and doors. And encourage more pollinators into the area by planting nectar-rich flowers among your tomatoes!)
You can also improve fruit set by hand pollinating. Now you could go from flower to flower with a small artist’s paint brush like this – and that would work, but a far more practical solution to dislodge the pollen to fertilize the female parts of the flower is to simply twang or tap on plant supports. By vibrating the flowers, you are mimicking the actions of a bumblebee to greatly enhanced pollination success!
Many gardeners struggle with extreme summer heat–and so can our tomatoes. When it gets too hot pollen becomes sterile, especially if nighttime temperatures fail to drop below about 77 Fahrenheit or 25 Celsius.
All you can really do is hold out for temperatures to fall away again. If your plants are under cover help them keep their cool by leaving windows, doors and vents wide open and perhaps adding blinds, cloth or greenhouse shading paint to filter out some of the sunshine.
Be sure to grow varieties suited to your climate too. If it’s particularly hot where you garden, seek out a warm-climate tomato variety that can better withstand your sultry summer.
If getting just the right temperature wasn’t enough to contend with, sometimes it can be a bit too humid… or dry for our tomatoes! Those close, uncomfortable conditions that come with high humidity can make pollen sticky, so that it clumps together and fails to drop onto the female stigma. Very dry conditions have the opposite effect–the flowers just aren’t moist enough for the pollen to properly stick, so it simply rolls off.
There isn’t much you can do about high levels of humidity other than ensure adequate ventilation and plenty of space between plants to help along airflow.
- Pruning off some of the lower leaves can help air to circulate better too.
- If bone dry air is your issue, however, be sure to keep plants properly watered and the humidity around your plants should remain more stable as excess moisture evaporates. Ensuring enough water will also give plants the resources required to fully swell their fruits, while reducing the risk of them simply dropping off.
- If you’re growing under cover, splashing water onto paving– known as ‘damping down’–will also help increase humidity.
Not Enough Light
If your tomato plants have lots of lush foliage but few flowers then consider light levels. Tomatoes love a sunny spot and will only do their thing if they receive a minimum of six hours direct sunshine a day. Dull weather presents a temporary challenge, but if you’ve planted them in a less-than-sunny position you may be best moving your plants to somewhere sunnier, because more sunlight means more energy to grow those fruits.
Finally, check what you’re feeding your tomatoes. Once the first flowers appear you need to be applying some sort of organic fertilizer that has a good level of both potassium and trace elements like magnesium. This will help to encourage exactly what we’re after: more flowers and better fruit set.
Use a product such as a liquid tomato feed or seaweed concentrate. This will help to promote healthier plants, reduce the risk of blossom end rot, and will up the final nutritional value of the fruits themselves. Most feeds are applied about once every two weeks by measuring out and diluting the concentrate according to the packet instructions, then watering it on at the base of the plants.
And don’t forget to aim for exemplary soil health anyhow, by incorporating plenty of well-rotted organic matter into your soil at least once a year. This will build up a thriving community of soil life, which in turn will help to support all your plants, including those lovely tomatoes!
For more information about growing and harvesting tomatoes, see the Almanac’s Tomato Plant Guide!