Why Tomatoes Develop Stunted Fruit After Flowering and How to Handle It

Your tomatoes flowered and set fruit, yet one by one they just sit there on the vine without growing? Those small, hard, stunted fruits are such a sorry sight. You clearly haven't skimped on watering or fertilizing, so where exactly is the problem? Today let's talk about the causes of stunted tomatoes and how to solve them. 

Why do perfectly good fruits get "freeze up"?
 
In fact, stunted tomatoes are mostly caused by "blocked development" during the flowering and fruiting stage. When key factors like temperature, fertilization and hormones go wrong, the fruits easily stop growing and end up hard and small, not even worth picking to eat.

Let's look at these 4 main causes:
 
1. Temperature: Tomatoes are especially sensitive to temperature when flowering. If the temperature is unsuitable, pollen vigor plummets; even if the flowers open, they cannot be properly fertilized, and the fruits naturally cannot grow large.
 
High temperature: when daytime temperatures exceed 30℃, especially under direct midday sun, the floral organs get sunburned and the pollen tubes develop poorly, so pollination simply cannot be completed;

Low temperature: when nighttime temperatures fall below 10℃, or when the temperature inside the greenhouse plunges during consecutive overcast and rainy days, the plant's metabolism slows down, nutrients cannot reach the fruits, and the fruits become "frozen stiff"

Suitable temperature: 25-28℃ during the day, 10-12℃ at night. During consecutive overcast, rainy or snowy days in winter, the night temperature can be appropriately lowered to 10℃ to reduce wasted nutrient consumption.

2. Hormones: Many people use fruit-setting hormones when growing tomatoes to keep the fruit, but if the concentration and timing are not right, it backfires.

Too high a concentration: above 25mg/kg, the flower stalk shrinks excessively, the nutrient transport channel is "blocked"

Wrong timing: applying the hormone before the flower is fully open, or only treating it when the flower is about to fade, will cause an imbalance in hormone action, resulting in either stunted fruit or deformed fruit;

Correct practice: treat the flower only when it is fully open, and follow the instructions strictly for concentration. Beginners can mix a little less to test first; it is better to be too dilute than too concentrated.

3. Fertilization: Too much nitrogen fertilizer, not enough potassium fertilizer, or a lack of calcium and boron during the tomato fruiting stage will all make the fruits turn stunted from "malnutrition."
 
Excess nitrogen fertilizer: leaves grow big and green and branches run wild, but the nutrients are all taken by the leaves and branches. The fruits don't get their "rations," so they stop at the small-fruit stage;

Excess phosphate fertilizer: too much phosphate fertilizer inhibits the absorption of potassium, and potassium is the "key element" that promotes fruit enlargement. Fruits lacking potassium are hard and small, and prone to cracking;

Calcium and boron supplementation falling behind: calcium makes the fruit skin firm, and boron promotes nutrient transport. If these two are lacking, the fruits not only become stunted but may also develop blossom-end rot.

Correct fertilization method: apply less nitrogen fertilizer during the fruiting stage, switch to a high-potassium fertilizer, and spray the leaves once every 10 days with high-potassium fertilizer+ sugar alcohol calcium. The undersides of the leaves can also be sprayed for faster absorption.

4. Environment: Consecutive overcast days, drought and lack of water, or alternating dry and wet conditions will keep tomatoes from getting enough nutrients, and the fruits naturally cannot grow.
 
Insufficient light: with more than 3 consecutive overcast days, photosynthesis is weak, carbohydrates are insufficient, and the small fruits stop growing from "lack of energy"

Water imbalance: after a long drought, sudden heavy flood irrigation causes the roots to suffer "stress" damage, reducing their absorption capacity, and the fruits become stunted from lack of water and nutrients. In winter, always use micro-irrigation for watering, not a direct heavy flush, and the water temperature should ideally be close to the soil temperature (15-20℃), to avoid shocking the roots;

Poor ventilation: when growing in a greenhouse or indoors, poor air circulation leads to poor pollination and easily breeds diseases, indirectly affecting fruit development.

Emergency tips: during consecutive overcast days, even without sun, you can spray some monopotassium phosphite on the leaves to quickly replenish nutrients. When the temperature is high at noon, ventilate for half an hour to get the air moving.