Article of the Week
Welcome to Brown County UW-Extension's
Natural Resources Program
(Originally published in the Green Bay Press-Gazette on June 17, 2018)
Ways to Minimize Plant Heat Stress
Temperatures in the high 80s and 90s can affect landscape plants in many ways. An increase in moisture loss is the foremost effect of heat stress on a plant. All plants dissipate their heat through an internal cooling process called transpiration, where the water is drawn from the root and is circulated into the leaf tissues and finally released into the air through specialized leaf tissue openings called stomata. Typically, many landscape plants and crops transpire more water than their own body weight even under a normal temperature range of 70° to 85° F. However, as the temperature rises above 85° F, water loss through the transpiration process increases to a rate where the roots cannot tap enough moisture to compensate for the water loss from the leaf tissue. This moisture stress forces the plant into a temporary wilting stage and if it continues, it can collapse the plant to death.
Here are some tips to minimize the impact of heat stress in your landscape and garden plants:
- Provide good soaking water to trees at least once a week. It is crucial to water newly-planted trees and shrubs (1-3 years old) for better establishment of their root systems. A general rule of thumb is to water one inch per week in heavy soil and 1.5 inches per week in sandy soil. It takes about 60 gallons of water to cover a one inch depth for 100 square feet. If trees and shrubs are mulched, place the soaker hose underneath the mulch to ensure the soil root zone gets adequate water.
- Before watering flowering annuals and vegetable crops, check the soil moisture by poking a finger an inch deep into the soil. If the soil is dry, give it a deep watering around the root zone area. Check the soil moisture status every day in container plants and raised beds.
- For medium and low quality turf, it is best to allow the grass to go dormant or water once a week to an inch deep if there is lack of rain.
- Maintain your lawn mowing height to about 3-4 inches. Mowing your lawn shorter than the recommended height forces the roots to stay closer to the soil surface and makes it vulnerable to heat and moisture stress injury.
- To encourage healthy deep roots to withstand drought stress, water the herbaceous perennials when the soil dries out moderately. Place the soaker hose directly into the soil and water it to a depth of one inch (0.6 gallons of water is needed to cover a one inch depth for one square foot). Certain herbaceous perennials may need more than one inch of watering.
- Avoid overhead watering of annuals, perennials, and trees to prevent foliar diseases. Water early in the morning to reduce evaporation loss.
- Mulch helps in conserving soil moisture. Use shredded wood mulch on trees, shrubs, and herbaceous perennials to a depth of 2-3 inches and keep the mulch at least 6 inches away from the main stem of the plant. Straw, rice hulls, leaf mold, peat moss, and hay are good sources of mulch on vegetable crops.
- Don’t fertilize plants during hot and dry periods, as fertilizer is a type of salt which can further dehydrate the plants by absorbing moisture from the root zone. Also, excess salt concentration can burn the feeder roots.
- Avoid pruning, transplanting, or digging of plants during stress periods.
- Avoid spraying lawn herbicides when temperatures exceed 85°F, as the herbicide can easily volatilize and can cause drift injury on desired plants.
Rice hull mulch works best in conserving soil moisture in annual flower and vegetable beds
2018 Master Gardener General Training
Master Gardener Volunteers are trained volunteers who aid the University of Wisconsin-Extension staff by helping people in the community better understand horticulture and their environment. This national program was introduced to Wisconsin in 1977. Today, the Master Gardener program is available in all 50 states and several countries. When you become a certified Master Gardener Volunteer, you will be automatically enrolled as a member of the NEW Master Gardener Association. The Association is a non-profit organization dedicated to horticulture education in affiliation with Brown County UW-Extension. The NEW Master Gardener Association is a chapter of the WI Master Gardener Association which connects you to a statewide network of Master Gardener Volunteers.
Horticulture Help Desk Services
We offer free consultations on lawn care advice, insect and disease diagnosis, and plant and insect identification. We also address tree and shrub problems as well as help you select the plants that are best suited to your needs and site. Soil tests and advanced diagnosis services are available for a fee.
Bring your live or digital specimen to the Horticulture Help Desk:
BROWN COUNTY UW-EXTENSION
210 Museum Place, Green Bay, WI 54303
Hort Help Desk Phone: 920-391-4615
The UW-Extension Office is open Monday through Friday from 8 AM to 4:30 PM.
If a horticulture staff member is not available when you call or visit, messages and samples can be left with UW-Extension reception, and a staff member will contact you.
We are here to serve you by connecting the University system, Master Gardener volunteers, and you - Northeast Wisconsin residents - to help things grow.
||Vijai Pandian - Horticulture Educator
Click here to email
||Brown County UW-Extension
210 Museum Place
Green Bay, WI 54303
||Monday - Friday, 8 AM - 4:30 PM