Horticulture Hotline 06-14-2021
Bill Lamson-Scribner
Although the “prime time” for planting has come and gone, with the wide use of containerized plants and new developments, I still get these types of questions regularly. Why are my leaves turning yellow and falling off? A plant’s leaves can be turning yellow and falling off for a number of reasons. Lack of oxygen to the root system, old leaves falling off making room for new leaves, mulch accumulation around the base of the plant, too much mulch and / or poor soil conditions could be causing your problems. Before you replace these plants, you need to determine why you are having trouble with the existing plants.
Lack of oxygen to the root system can be caused by many situations. The plant could have been planted too deep. When you peel back the mulch, you should see the top of the original container soil right at the surface. Pull out one of your dead plants and see if the roots have been growing out into the soil or just circling around the original container soil. Sometimes with plants and especially azaleas, the roots tend to stay in the pine bark/sand mix that they are grown in at the nursery and never venture out into the native soil. The roots get so tight that they repel water and eventually die. When you plant a plant, be sure to break up the root ball and encourage the roots to grow out into the native soil.
The soil could be clay or heavy that does not allow space for oxygen. The area could be low or over-watered. Most plants like a well-drained soil. If the soil stays wet, most plants will not be happy. Hollies, azaleas, camellias, boxwoods and most other plants like moist soil, but not wet feet.
One old drainage test is to dig a hole the size of your container. Fill the hole up with water and see how long the water takes to drain out of the hole. If the water takes hours to disappear, you know you have some work to do.
In the early spring, sometimes you will have leaves that are turning yellow and falling off. This is a natural occurrence as old leaves are falling off making room for new leaves.
Magnolias, live oaks, azaleas and gardenias are the plants that we get the most calls on in the stores when this occurs. This is natural and some plants seem to do it more than others.
Years of mulch pilling up or placing mulch on the stem of the plant can lead to disease, entry points for insects, or an area where adventitious roots can develop. The roots of plants can handle moist conditions; however, the stems cannot.
Most of the plants here like a high organic soil, unfortunately in the Lowcountry, this is rarely the case. Before you replant, evaluate your soil visually and with a soil test. If your soil doesn’t have organic matter in it already, you would want to amend with Cotton Burr Compost, or Natures Blend. Try to amend the entire bed area and not just the planting hole. We see a lot of dead plants where people have amended the planting hole and the amendments break down over time and the plant sinks as a result. Don’t ever dig a hole deeper than the depth of the ball or the container of the plant. If the plant sinks over time, it is the same as planting it too deep originally. Also test your soil for any nutrient deficiencies or surpluses. By amending your soil from the lab results and amending your soil with organics, you will increase your odds of having a successful planting.
With the recent rains watch for fungus in the lawn, fire ants popping up, mosquitoes, flies, wasps, roaches moving indoors, rats, mice and drainage issues.
Bill Lamson-Scribner can be reached during the week at Possum’s Landscape and Pest Control Supply. Possums has three locations 481 Long Point Rd in Mt. Pleasant (971-9601), 3325 Business Circle in North Charleston (760-2600), or 606 Dupont Rd, in Charleston (766-1511). Bring your questions to a Possum’s location, or visit us at possumsupply.com. You can also call in your questions to “The Garden Clinic”, Saturdays from noon to 1:00, on 1250 WTMA (The Big Talker). Saturday's show is replayed Sunday from 11:00 - Noon.
