Tomato watering guide

How often and how much water do tomatoes need? There is probably no perfect answer to this question, but our team has created an informative watering guide to make using the GRAAS irrigation system as simple and effective as possible.

On average, each tomato plant requires between 20 and 35 liters of water per week, though weather conditions, soil quality, and growing methods can significantly influence this amount. Tomatoes should be watered generously but infrequently. In cloudy, cool weather, water requirements may drop by half, while on hot, sunny days they may increase by up to 50%. To ensure the best growing conditions, we recommend maintaining the proper soil moisture level.

How much water does a tomato plant need in ml?

In milliliters, a mature tomato plant needs roughly 2,900–5,000 ml of water per day (20–35 liters per week). Smaller plants need much less. Typical daily amounts per plant:

Growth stage	Water per plant per day
Seedling (just transplanted)	200–500 ml
Young plant (vegetative growth)	500–1,000 ml
Flowering	1,000–2,000 ml
Fruiting, mature plant	2,900–5,000 ml
Hot, sunny summer days	up to 5,000–7,000 ml

In cool, cloudy weather these amounts can drop by half. Rather than pouring the full amount at once, it is best to deliver water in small, frequent doses at the base of the plant — exactly what a drip irrigation system with a soil moisture sensor does automatically.

Your growing method also affects water needs. Tomatoes grown directly in soil require more water, while those in bottomless pots need slightly less. Average soil moisture during the day should remain between 60% and 85%, and at night between 65% and 75%.

For tomatoes to grow large, healthy, and attractive, they must be watered frequently with small amounts of water. With the GRAAS irrigation system, this important task becomes much easier. By maintaining the right soil moisture level, you ensure optimal plant growth and reduce the risk of various diseases.

Incorrect water amounts and soil moisture levels can quickly and severely damage your tomato plants, but these issues can be detected by visually inspecting the plants.

Signs of overwatering

Yellowing leaves, root rot, mold, cracked fruit skin, slow growth, and unpleasant odor are key indicators of overwatering. The simplest way to avoid this is to reduce the amount of water given to the plant and ensure proper greenhouse ventilation. If the soil is excessively wet, replace part of it with fresh, dry soil.

A tomato cracked due to insufficient water.

Signs of underwatering

When tomatoes receive too little water, the soil dries out, plant growth slows, and the plants begin to wilt. Leaves curl, twist, and dry up. To avoid these problems, gradually increase the amount of water provided — slowly and regularly.

Tomato leaves curled due to insufficient watering.