By Eddie Ayers, County Extension Agent
In last week’s article I listed the top 10 reasons for yellow leaves on your plants (under watering and overwatering, which top the list, lighting, temperature, soil condition, nutrients or lack thereof, pests, disease, transplant shock, and age) and pointed out that it may take weeks or even months for your plant to recover from whatever is causing the yellow leaves and return to normal growth. The reality is that if you can’t provide the proper environmental conditions for your particular plant’s needs then it can’t thrive. Last week I discussed four reasons why plant leaves turn yellow and this week’s article is about the remaining six reasons plants have yellow leaves.
Nutrient deficiencies are often indicated by yellowing foliage. Iron deficiency is very common. This causes yellowing, stunted growth and interveinal chlorosis. Have your soil tested and maintain a pH below 7. Potassium deficiency can also cause yellow leaves, sometimes on the edges and tips of the leaves, and sometimes it will be yellow between veins. Composted fruit and vegetables added to the soil can help provide the needed nutrients. Nitrogen deficiency can be indicated by stunted growth, yellow edges on tips of leaves, and the veins of the leaves may be yellow; sometimes the entire leaf will be pale or yellow. Adding compost will help and adding coffee grounds to the soil is a great alternative. Magnesium deficiency shows as interveinal chlorosis, between the veins. Treat the soil with Epsom salts or compost. Calcium deficiency causes crinkled, mottled, or distorted leaves. Adjusting soil pH can help, though be aware that adjusting soil pH occurs slowly over time and the pH may eventually creep back up to its “natural” level.
If yellow spots on your leaves appear along with tiny critters (be sure to check the undersides of the leaves) then you have an insect population that’s enjoying your plants a little too much. First identify the pest and then treat for that particular insect. Remember that often pests are so little they cannot be seen with the naked eye, but their damage is obvious. Typical insect infestations on houseplants are caused by one of the following: mites, aphids, mealybugs, thrips, scale, or whiteflies. Repeatedly washing the plants or applying an insecticidal or horticultural soap is one treatment that is often effective as well as environmentally safe.
When conditions are right, plant host, moisture, and spores diseases attack plants. They may start out as small spots, but because they disrupt the plants ability to produce chlorophyll, leaves turn yellow. Sprays won’t turn the leaves back to green, but it may prevent damage to newer leaves. If you do spray for bugs or diseases, always read and follow the label directions.
When a plant is moved from a container or from one location to the other it can often suffer from transplant shock. Try to make sure that the hole you are using for the new plant is big enough to allow the roots to spread and get established. Proper watering is also essential to avoid leaves turning yellow.
In some cases, leaves simply just age-out, slowly yellowing over time, the plant’s natural life cycle. Probably the most dramatic example is the seasonal cycle of white pine (Pinus strobus); its older interior needles all turn brown in the fall and seemingly drop at once, usually in the spring. Many species of pines will retain their older needles for about three years, and then eventually the older interior needles of the tree will drop.
Remember that our plants really do “talk” to us. We simply must understand their “leaf” language. For more information, contact me in the Gilmer County UGA Extension office.
Susan Jasan, horticulturist and landscape architect, and State-By-State Gardening contributed to these articles.