How much water to give plants?

Posted7/8/2018 6:00 AM

Q. Now that the weather is hot, how often should I be watering my vegetables and ornamental garden?

A. Basically, the watering requirements for vegetables and ornamentals are the same.

Water vegetables and ornamentals once a week during dry spells when less than 1 inch of rain falls during a week. About 1 inch of water a week, including rainfall, is desirable for plants during the growing season. When temperatures exceed 90 degrees, plants may need 2 inches of water per week.

Water the soil, not the plants. Keep the leaves as dry as possible and water early in the day to reduce chances of diseases and lessen evaporation. It is better to soak the soil thoroughly to a depth of at least 6 inches than to sprinkle the garden lightly at frequent intervals.

The water should get down to the root zone of the plant. Soaker hoses work best for this. Soaker hoses with holes can be used by placing the holes on the bottom side. It may take 3 to 4 hours to do a thorough soaking.

Consistent soil moisture is key to healthy plants and good vegetable production. For example, tomato cracking and blossom end rot can be more severe with fluctuations in watering.

Summer and fall vegetable gardens often require water to establish the crop because the soil has dried out during the summer months. If the soil is dry when you are ready to plant, apply one-half to 1 inch of water uniformly to the area to be planted. After the water is added to the topsoil, lightly work the surface using a rake or very shallow cultivation. Seed the vegetables, but don't administer additional water for one to two days. If it doesn't rain for two days after planting, apply about one-half inch of water every other day until the seed germinates.

After planting vegetables or ornamentals, add a 2- to 3-inch layer of mulch around the plants. Use slightly different mulch for your vegetables. Straw, compost or thin layers of grass clippings are recommended. For an ornamental garden, use organic materials such as compost, shredded bark or dry grass clippings. This will help reduce weed growth, retain soil moisture, alleviate high soil temperatures and add organic matter. Applying more than 4 inches of mulch may deprive roots of oxygen, plus excessive mulch can make it more difficult for any water to reach the roots.

-- Terri Passolt

• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email Visit

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