Tomato watering guide
How often and how much water do tomatoes need? The short answer: each tomato plant needs on average 20–35 liters of water per week (roughly 2,900–5,000 ml per day when fruiting), with soil moisture held at 60–85% during the day and 65–75% at night. Weather, soil quality and growing method can shift these numbers considerably — what matters most is a stable moisture level, not a fixed schedule.
| Parameter | Target for tomatoes |
|---|---|
| Water per week | 20–35 L per plant (~2,900–5,000 ml/day) |
| Soil moisture, day | 60–85% |
| Soil moisture, night | 65–75% |
| Cloudy, cool weather | Needs can drop by half |
| Hot, sunny weather | Up to 50% more water |
Your growing method matters too: tomatoes in open soil need more water, while bottomless pots need slightly less. For big, healthy plants, water frequently in small doses — exactly how the GRAAS irrigation system works: set the target soil moisture level and it maintains optimal growth while reducing disease risk.
How can you tell tomatoes are overwatered?
Yellowing leaves, root rot, mold, cracked fruit skin, slow growth and a bad smell are the main indicators of too much water. The simplest fix: reduce the water dose and ensure proper greenhouse ventilation. If the soil is very wet, replace part of it with fresh, dry soil.
How can you tell tomatoes are underwatered?
The soil dries out, growth slows, plants begin to wilt, and leaves curl, twist and dry. Increase the water amount gradually — in slow, regular steps.
A tomato cracked from insufficient water.
Tomato leaves curled due to insufficient watering.
Frequently Asked Questions
How much water do tomatoes need per week?
On average 20–35 liters per plant — about half that on cloudy days, up to 50% more in hot weather.
Why do tomato fruits crack?
Uneven watering: after a dry spell, a heavily watered fruit grows faster than its skin. Stable soil moisture solves it.
Can tomato watering be automated?
Yes — the GRAAS iRigator waters based on real soil moisture, holds the 60–85% range, and shows everything in the app.