Planting tomatoes can bring the joy of gardening and the satisfaction of eating nutritious fruits. However, the key to enjoying ripe tomatoes lies in the successful fruiting of tomato plants. Experts have shared some reasons why tomatoes may fail to flower and fruit properly, which is worth paying attention to.
Horticulture expert Katy Willis wrote on the home living website “House Digest” that various factors, including an excess of nitrogen fertilizer, can lead to a reduction in tomato flowering or cause flowers to drop before pollination. Even if the flowers do not drop prematurely, factors such as lack of pollinating insects or excessively high temperatures and humidity can hinder the pollination process.
Willis mentioned common reasons why tomatoes may fail to flower and fruit properly, listing ten of them:
Whether synthetic or natural fertilizers, high nitrogen fertilization can pose problems for many plants, especially fruiting crops like tomatoes. This is because nitrogen promotes leaf growth, redirecting plant energy that should be used for flowering, fruiting, and root development towards leaf growth. This is not desirable for tomato cultivation.
If plants already show signs of stress, applying excessive fertilizer or nitrogen at this point will further burden them. Instead of preserving energy or using it for self-repair (to cope with stress factors), over-fertilization forces them to expend energy on rapid leaf growth.
Just like humans, tomatoes do not thrive in heatwaves. When daytime temperatures exceed 90°F (approximately 32°C) and nighttime lows stay above 70°F (approximately 21°C), tomato pollen becomes sticky and loses its viability. In such conditions, even if the plant produces many flowers, fruit setting may not occur.
Tomatoes also do not tolerate cold temperatures. If nighttime lows drop below 55°F (approximately 13°C), flowers may drop. Even with sufficiently high daytime temperatures, extreme cold like extreme heat inhibits pollen tube growth, suppressing pollen production. Without successful pollination, fruits cannot develop.
Tomatoes dislike hot, humid weather. When relative humidity exceeds 80%, their pollen becomes sticky and cannot be dispersed properly. Even with suitable temperatures and abundant bee activity, this condition can lead to poor or incomplete pollination, resulting in reduced fruit setting or no fruit at all.
Although tomato flowers contain both male and female parts, they cannot self-pollinate. While wind assistance aids pollination to some extent, insect pollination remains the best way to ensure successful fruit set.
Tomatoes rely on wind or insect-induced vibrations to shake loose pollen and complete self-pollination to develop fruits.
Most people do not pay special attention to the structure of tomato flowers. By carefully observing the flowers of heirloom tomato varieties, one may note many flowers with exposed pistils instead of enclosed within the anthers. Without insect “buzz pollination,” this structure makes pollination significantly challenging.
This phenomenon, known as “exserted stigma,” is exacerbated by high temperatures. In hot environments, plants push the stigma further out, decreasing successful pollination rates and reducing fruit setting.
If tomato plants only flower but bear few fruits without any other apparent reasons, conducting soil testing becomes necessary.
A deficiency in phosphorus or potassium in the soil can lead to low fruiting or no fruiting at all. Phosphorus deficiency weakens plants, slowing down their growth and maturation, while potassium deficiency causes browning of leaf edges and overall plant health decline. Both scenarios result in plants flowering without producing fruits.
Insects like the tarnished plant bug can attack tomato plants, feeding on developing flower buds and fruits voraciously. If you notice tiny puncture marks on young flower buds, it’s a clear sign of these pests.
Damage from tarnished plant bugs can cause wilting and dropping of flowers and young fruits or the formation of sunken scars known as “catfacing.”
Additionally, mites can severely harm tomato flower buds, leading to distorted plant growth and leaf bronzing – symptoms easily mistaken for herbicide damage or nutrient deficiencies.
Tomatoes require consistent, adequate water supply to produce quality fruits. They are averse to fluctuating water levels, where drought and excessive watering alternate. These water fluctuations put immense stress on the plants, leading to flower drop. If fruit development has started, it might trigger blossom end rot.
When watering tomato plants, it’s crucial to water as close to the soil near the roots as possible. Watering from above can moisten leaves, creating ideal conditions for fungal spores to thrive, causing plants to fall victim to wilt diseases.
If your tomato plants exhibit delayed growth, yellowing leaves, abnormal curling, flowering cessation, or fruit setting interruption, diseases like beet curly top or tomato yellow leaf curl caused by viral infections may be to blame.
The former is transmitted by leafhoppers between plants during feeding, while the latter is spread by whiteflies.
Tomatoes are highly sensitive to drift from broadleaf herbicides (and related pesticides), even slight exposure can cause damage.
Minor drift can result in banded, twisted, or cupped new tomato leaves. Severe drift may inhibit flowering, lead to flower and fruit drop, or even plant death.
Plants affected by herbicide drift cannot recover. Since the specific herbicide cannot be identified, it’s advisable not to consume fruits from affected plants.
Depending on the type and amount of chemical substances involved, the aforementioned symptoms may appear within hours or take a week or longer to manifest.