Yard and Garden: Lawn, Annual and Garden Care in Hot Weather

Iowa State University Extension specialists offer tips for taking care of your lawn, annuals and garden in hot weather. To have additional questions answered, contact the experts at hortline@iastate.edu or call 515-294-3108.

Is it necessary to water an established lawn during hot, dry weather?

Gardeners have two basic options when confronted with hot, dry weather. One option is to do nothing and allow the grass to go dormant. The alternative is to water the turfgrass during dry weather to maintain a green, actively growing lawn.

Cool-season grasses, such as Kentucky bluegrass, can survive long periods of dry weather. In dry weather, the shoots of the turfgrass plants stop growing and the plants go dormant. Dormancy is a natural survival mechanism for turfgrass. While the leaves have turned brown and died, the turfgrass roots and crowns remain alive. Generally, Kentucky bluegrass can remain dormant for four to six weeks without suffering significant damage.

Cool-season grasses are at risk of dying if dormant for more than six weeks. To ensure survival of dormant grass, it’s best to water lawns that have been dormant for six weeks. Apply 1 to 1 ½ inches of water in a single application. Water again seven days later. The grass should begin to green up after the second application. 

When is the best time to water a lawn? 

Early morning (5 to 9 a.m.) is the best time to water a lawn. A morning application allows the water to soak deeply into the soil with little water lost to evaporation. When watering is completed, the turfgrass foliage dries quickly. Watering at mid-day is less efficient because of rapid evaporation; in addition, strong winds may cause uneven water distribution. Strong, mid-day winds also may carry water onto driveways, sidewalks or streets, wasting considerable amounts of water. Watering lawns in late afternoon or evening may increase disease problems.

How frequently should I water my lawn?  How much water should be applied per week?

Most cool-season lawns in Iowa require approximately 1 to 1 ½ inches of water per week. When watering the lawn, apply this amount in a single application or possibly two applications three or four days apart. Avoid frequent, light applications of water, which promote shallow rooting and lush growth. Lush, shallow-rooted turfgrass is less drought tolerant. It also is more susceptible to pest problems. To determine the amount of water applied by a sprinkler, place two or three rain gauges within the spray pattern. 

How frequently should I water annuals in containers? 

The frequency of watering may vary considerably from container to container. Watering frequency depends on the size and type of container, composition of the potting mix, plant species and weather conditions. Some plants, such as impatiens, like an evenly moist soil. Others, such as vinca, possess good drought tolerance.

Annuals growing in containers should be checked daily (especially in summer) to determine whether they need to be watered. A few plants, such as New Guinea impatiens and fuchsia, should be checked twice a day (morning and late afternoon or evening), as they dry out quickly on hot, windy days. 

When watering annuals in containers, continue to apply water until water begins to flow out the drainage holes in the bottom of the container.

How often should I water my garden?

A deep watering once a week is usually adequate for fruit, vegetable and flower gardens. When watering the garden, water slowly and deeply. Moisten the soil to a depth of 8 to 10 inches. Most annuals, perennials, vegetables and small fruits perform best when they receive 1 to 1 ½ inches of water per week (either from rain or irrigation).