Our home landscape plants and lawns suffer from various problems throughout the year. Many issues result from pests, such as insects, fungal diseases, wildlife and others.

However, our garden plants can also suffer from nonliving causes, often termed abiotic. Examples include chemical damage, temperature extremes, too much or not enough water, inadequate or excessive sunlight among other examples.

Knowing how to distinguish living from abiotic causes will help keep your landscape healthy and attractive.

When I worked in commercial landscaping back in the 1980s and ’90s, one day, I arrived at a job site and noticed several of the plants had dark dead spots all over them. They consisted of shore junipers, hollies, forsythias, begonia, and zoysiagrass. Everyone had the same symptoms. Since plant diseases and insects are specific to the species of plants they attack, the issue was not the result of living organisms. Another crew was onsite a week earlier and misapplied an herbicide, thus damaging all the plant material.

Sometimes symptoms can be similar for both biotic and abiotic causes. For example, if the leaves on an azalea are turning yellow, many would deduce the cause is lack of fertilizer. That may be true.

However, the plants could be suffering from lace bugs, which are tiny insects with pierce-sucking mouthparts that cause the leaves to develop a yellow mottled appearance. Another possible cause is root rot resulting from water-logged soils. To determine the source of the issues, you need to thoroughly examine the plant to find out the exact cause, which can be challenging.

If you have plants suffering, check the environmental conditions and see if they have the right site conditions. Azaleas will suffer and decline in full sun and are more susceptible to lace bugs. They prefer partial shade. Bermudagrass, on the other hand, needs full sun to thrive. The grass is tough in handling heat, drought, and compaction but will deteriorate in the shade.

The plants should be tolerant of our climate. Citrus plants cannot grow year-round in our area due to the freezing temperatures. Oleanders, large shrubs with colorful flowers, thrive along the Georgia coast; however, in Gwinnett, they can suffer from the hard freezes. Conversely, many other plants suffer in our summer heat. Once a resident contacted the Extension office to find out what was troubling his Alberta spruce. The tree was turning brown and declining. The cause was in the name — Alberta. Since we are not in Alberta, but Georgia, our weather conditions are too hot; thus, these trees should not be planted here.

Fertilizer and pH also play an essential role in plant health. Soil pH plays a vital part in nutrient availability to the plant. Most plants do best at a pH between 6.0 to 7.0. However, some require more iron, which is more plant available at a lower pH. These plants include azaleas, rhododendrons, camellias, blueberries, and mountain laurels.

If the pH is too high, they suffer from iron deficiency and develop “chlorosis” — which is a light green to yellow to the white coloration of the leaves. Thus, if you grow any of these plants, ensure the soil is at the appropriate pH. Have your soil tested for pH and nutrients through UGA Extension Gwinnett.

If you are having issues with your landscape plants and cannot determine the cause, please contact the Extension office for assistance. You can even send pictures with descriptions to my email address (tdaly@uga.edu).

UGA Extension Gwinnett is taking orders for our annual plant sale. They include several types of fruiting plants as well as ornamental ones. For more information and to download a form, go to: https://tinyurl.com/22tx2d79 or contact the Extension office to have one mailed to you.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with UGA Extension Gwinnett.


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