Reasons why tomato fruits expand slowly and how to solve them

When the tomatoes you grow at home swell slowly and stay on the small side, it is usually caused by a combination of factors such as variety, nutrition, environment and management. Today let's talk about the causes and the solutions, so even beginners can master them easily!

I. Causes

Variety: blindly introducing varieties that do not suit the local climate and soil conditions, such as growing varieties that cannot tolerate heat and humidity in the hot, rainy south, or planting temperature-sensitive imported varieties in the cold northern regions, will both hinder fruit growth.

Nutrition: excessive nitrogen fertilizer causes the plant to grow leggy, with nutrients supplied to the stems and leaves first, leaving too few nutrients for fruit development; calcium deficiency easily triggers blossom-end rot and fruit cracking, potassium deficiency leads to small fruit and poor colouring, and boron deficiency affects pollen germination and pollination, all of which directly hinder fruit swelling; problems such as soil compaction and salinization reduce root activity and lower nutrient uptake efficiency.

Temperature:

1.When daytime temperatures stay above 35℃, the activity of photosynthetic enzymes drops and organic matter synthesis is blocked; when night temperatures are too high (>20℃), respiration is too strong and consumes a large amount of nutrients.

2.When night temperatures fall below 10℃, root absorption capacity weakens, plant growth stalls and fruit development slows down.

Light: continuous rainy weather or hazy days result in insufficient light duration of 6hours, which affects photosynthesis; poor light transmission of greenhouse film, excessive planting density (plant and row spacing <50cm×80cm) or a closed canopy of branches and leaves all cause uneven light exposure for the plants.

Cultivation: leaving too many fruits per truss disperses nutrients and makes it hard for the fruits to develop fully; too many side shoots and old leaves that are not removed lead to poor ventilation and light penetration and make pests and diseases more likely; soil that alternates between dry and wet, or flood irrigation that starves the roots of oxygen, affects nutrient transport.

Pests and diseases: early blight, grey mould, root-knot nematodes, whitefly and other pests and diseases directly harm plant health and destroy the vascular system, blocking nutrient transport.

II. Solutions

1.In the south, choose heat-tolerant, disease-resistant varieties; in the north, choose cold-tolerant varieties that store and transport well.
 
2.Use a balanced water-soluble fertilizer at the seedling stage to promote strong seedlings; during the fruit-swelling stage use a high-potassium water-soluble fertilizer+ monopotassium phosphate, applied as a drench 1time per week; use a calcium-magnesium-boron-zinc foliar fertilizer sprayed 7-10days 1time, focusing on new leaves and fruits; add more bacterial fertilizers such as Bacillus subtilis and EM bacteria to improve the rhizosphere environment and raise nutrient use efficiency.

3.Maintain 25-30℃during the day, and ventilate promptly or use shade netting to cool down once it exceeds 32℃; keep it at 15-18℃at night, and cover with insulating quilts or add heat lamps when temperatures are low;

4.Keep 2-3fruits on the first truss, and for weak seedlings remove the first truss of flowers to concentrate nutrients on growing a strong plant; use single-stem or double-stem training and remove side shoots and diseased leaves promptly; follow the principle of "water when dry, let dry between waterings", water little and often, and avoid flood irrigation; in hot summer weather, water in the early morning or evening; cultivate the soil 1time a month to a depth of 5-10cmto break up compaction and promote root growth.

5.Spray protective fungicides regularly; hang yellow and blue sticky boards to trap pests; once pests or diseases are found, choose high-efficiency, low-toxicity products, such as difenoconazole for early blight and imidacloprid for whitefly, and use them strictly at the concentration stated on the label.
 
In short, as long as you master the points above, you can easily solve the problem of tomatoes failing to swell.