Hawaii’s home gardens and landscapes are revealing signs of stress, signaling just how much high summer temperatures have taken a toll on plants in our backyards. Starting as early as May, temperatures begin to increase to 85 degrees and keep climbing to 90 degrees while sunlight hours increase and rainfall decreases.

Sunlight fluctuates in the Hawaiian Islands, peaking at a little over 290 total hours in July and dropping to about 200 hours by February.

The accumulative stress of climbing temperatures, peak sunlight and lower rainfall over the past few months has resulted in more inquiries from home gardeners to University of Hawaii Master Gardeners. After probing for details, they are deducing symptoms are due to heat or climatic stress.

Climatic stress symptoms cannot be treated by supplementing with more water or fertilizer. The best prescription is to add a layer of mulch, keep a consistent watering schedule and wait for the winter months when plants can recover.

Being knowledgeable about the signs of plant stress can tell you secrets about your landscape.

Leaf scorch symptoms include brown edges on the leaves of trees and shrubs. When plants are over-watered or over-fertilized, it pushes excess water and nutrients to the leaves and leaf margins. The sun scorches the accumulation of water and excess fertilizer and burns this part of the leaf.

Pruning branches that show symptoms, adding a layer of mulch, being careful to not over-water and restricting fertilizer are recommended. Time is your best tool to see the most improvement.

Maybe you see wilting leaves in the landscape. The soil might appear to be damp, or even pooling water can be seen. The plant is telling us that its root systems have worked hard in the past months fighting high evaporation rates and little water to replace water loss. In this case root structures may have been damaged by stress. Watering more only increases the chance of root decay. With mulch and time, the plant should start to recover in a month’s time.

To prevent water stress, we recommend a good layer of mulch within the drip line of your tree or shrub. During high-temperature months, the mulch will work to keep the roots cool and provides a barrier from sunlight, preventing soil from drying out.

Weeds compete for water and nutrients. Be sure to clear weeds from landscaped areas. Consider removing grass at the base of trees and shrubs. To protect tree roots, avoid parking on the grass under landscape trees.

Learn more at ctahr.hawaii.edu/UHMG, search for “Tropical Topics.” To find a UH Master Gardener, click on your island name.

Jayme T. Grzebik is an urban horticulturist and statewide coordinator for the University of Hawaii Master Gardener program.