How Often to Water Tomatoes, Plus 6 Tomato Watering Tips

Knowing how often to water a tomato plant can challenge beginner and experienced gardeners alike. Excessive watering can result in diseased plants and rotten tomatoes. But not watering often enough may weaken plants and give you small, mealy fruit. The trick is to pay attention to your soil and the cues your plants give you so you can grow armloads of delicious, juicy tomatoes. These tips will help you figure out exactly how often to water tomatoes for the best harvest.

Know Your Soil

The best soil for tomatoes is moist to the touch but not sopping wet. Be wary of soil that is dripping with water when you squeeze it together in your hand; too much soil moisture limits the oxygen available to plant roots, slowly suffocating the plant. Soil that is excessively crumbly, dry, or dusty has very little moisture available to plant roots.

Soil that contains a lot of sand doesn't hold water well and dries quickly. Because of this, tomato plants growing in sandy soil may need to be watered more often, about every three or four days. Clay soil, on the other hand, holds water well. Plants growing in clay soil usually only need to be watered once a week. Tomatoes growing in pots often demand daily water because the limited soil volume in containers dries out quickly. 

The very best way to know if it’s time to water your tomato plant is to grab a handful of soil from a couple of inches below the soil surface. This is dirty work but is truly the most accurate way to know if you should add more water. If the handful of soil feels moist, wait a day and check it again. But if the soil is dry to the touch, water the plants deeply. 

Watering Tomato Plants with Fruit

If you're checking the soil moisture by hand regularly, you’ll notice the soil drying more quickly when fruit begins to form. Tomato plants have high water needs when producing fruit; the roots pull moisture from the soil more quickly during fruiting than when they were just growing stems and leaves earlier in the season.

Again, monitor the soil regularly to judge your plant’s water need. Plants that were watered once a week early in the season will likely need to be watered more often when they start producing fruit. Keep watering frequently through tomato harvesting season.

Tips for Watering Tomato Plants

Once you've figured out how often to water a tomato plant based on your soil's moisture levels and the plant's life cycle, use the following tips for watering your tomato plants properly.

1. Deliver water to the base of the plant.

Avoid getting leaves and stems wet when watering tomatoes. Bacterial and fungal tomato diseases are spread more easily when the foliage is wet. Instead, deliver water directly to the base of a plant using a watering wand, drip hose, or watering can with a long spout. 

2. Water slowly.

Water from a fast, heavy rain shower often flows away from plants instead of soaking into the soil. The same is true when plants receive a blast of water from a garden hose or watering can. Turn down the flow on your garden hose or water slowly when using a watering can. Better yet, use a drip hose to slowly soak the soil.

3. Soak, soak, soak.

When watering aim to soak the soil to the depth of 10 inches. Deep watering promotes a deep root system. A deep root system will not only anchor the plant in the ground well, it will also equip the plant to reach far and wide for water when needed. 

4. Check the depth.

After a watering session, use a garden trowel to dig a narrow, 10-inch-deep hole about 5 inches from the base of the plant. If the plant has been watered adequately, soil at the bottom of the hole will be moist. Adjust watering time in the future if needed. 

5. Add a layer of mulch.

Conserve soil moisture by spreading a 2-inch-thick layer of organic mulch over the root zone of a tomato plant. The mulch will insulate the soil, preventing big temperature swings. Mulch also helps to keep water-stealing weeds at bay, and will slow down soil moisture evaporation. Shredded bark mulch and weed-free grass clippings are good choices. 

6. Check containers daily.

Tomatoes growing in pots have high water needs. The relatively small soil volume in the container limits the amount of water available to plants. During the heat of summer, container-grown tomatoes often need to be watered daily. Hot, windy conditions might require twice daily watering.