Watering Tomatoes: How Much and How Often

Full-grown mature tomato plants easily use 2-3 gallons of water daily, sometimes 4-5 gallons. How do I know? I use self-watering containers with 3-4 gallon reservoirs. During peak season, bigger plants can drain them in a couple days.

Where Does All That Water Go?

About 80-90% of the water taken through roots transports minerals, nutrients, and fertilizer throughout the plant. Some evaporates from soil. After delivering nutrients, most water eventually evaporates as vapor through the leaves.

Quality Soil Saves Water

Using potting mix with lots of sphagnum peat moss keeps soil moist but not soggy. One pound of sphagnum peat moss holds up to 25 pounds of water. With great potting soil, you save water and don't need to water as often.

See our complete potting soil guide →

Best Time to Water

Water in the mornings if you can. Any excess water on leaves or soil surface evaporates quickly with morning sunshine. Evening watering leaves surface soil wet too long, inviting disease.

Keep Water Off the Leaves

Avoid getting water on leaves. Prevent lawn sprinklers from spraying or misting tomato leaves. Too much water on leaves invites disease.

If you must get water on leaves, do it during the day when it dries quickly.

How to Water Containers

Slow water until water comes out the overflow hole on self-watering containers or out the bottom drain hole on regular containers. Standard 20-25 gallon containers hold about 4 gallons of water.

Use a Moisture Meter

Everyone should have a moisture meter. They cost about $10 at big box stores, plant nurseries, or online.

There are three zones on the meter: Dry, Moist, Wet. When it gets close to Red Dry, time to water. Remember—when using great potting soil, you can't overwater.

Deep Water Pipes (Optional)

If you have deep water pipes installed, fill each pipe a couple times every time you water. Slow water around the base of the plant, then fill the deep water pipes.

Learn about deep water pipe installation →

---

Next Steps

Choose water-retaining soil →
Select proper container size →
Master the fundamentals →

Dave Freed / The Tomato Guy