Help Plants Beat the Hear in Your Late-Summer Garden

Although this summer in northeast Washington has felt comfortable to some, statistics show we had record hot temperatures in July, and forecasters speculate about the hottest September on record. September will bring some relief, but periods of high temperatures will still test your garden's resilience. Here are key strategies to maintain plant health and productivity as the harvest season continues.

Watering is essential. Maintaining moist soil is a top priority. Pay close attention to areas that get full sun, as they can dry out the quickest. A good rule is to water when the top one or two inches of soil feels dry to the touch. Penn State master gardener Christa Shoreman recommended an inch of water weekly for plants in the garden. For a more efficient approach, consider using watering stakes or tubes for larger plants like trees and shrubs. These deliver water directly to the roots, minimizing waste from evaporation. Similarly, a soaker hose or drip-irrigation system with a slow flow can ensure water penetrates deep into the soil where it's needed most.

Mulching for moisture retention. Mulch is a gardener's best friend. It can act as a protective layer that not only helps the soil retain moisture, but also shields plants and their roots from extreme heat. Mulching materials include wood chips, bark chips, and even deciduous leaves. If you're using a soaker hose or drip line, a layer of mulch on top can further reduce water loss through evaporation. For all watering, try to do it in the morning to give the plants a good drink before the midday sun.

Caring for container gardens. Plants in containers may be particularly vulnerable to heat. Their confined root systems and the rapid heat absorption of their pots mean they can dry out at an alarming rate. In the middle of summer, container plants may need to be watered as often as twice a day to keep them hydrated and healthy.

Establish a consistent routine. A simple, repeated routine can help keep a  garden healthy. As one Pacific Northwest gardening blogger, Erica, wrote, adopt the mantra, "Weed, water, mulch. Repeat, repeat, repeat." She also emphasized the importance of a continuous cycle of harvesting, picking, and gathering to encourage more production.

Specialized care for specific plants. Some plants have unique needs that require extra attention during the heat. Keep a close eye on fruiting plants such as cucumbers, beans, and peppers. Also, any transplants or seedlings recently put in for a fall or winter garden will need consistent watering to get established. Finally, don't forget about camellias; a deep watering now is crucial to help them develop the flower buds that can bring beautiful blooms next spring. On the flip side, cut down on watering trees, shrubs and vines to harden them for winter, according to Oregon State University.

The WSU Extension Master Gardener Program trains volunteers to be effective community educators in gardening and environmental stewardship. Master Gardeners provide information generated from research at WSU and other university systems. Kathy Hansen, an educator and writer who lives in Kettle Falls, has been a Master Gardener volunteer since 2019.