Why are the leaves on my tropical hibiscus turning yellow? -Carol
If your tropical hibiscus has a few yellow leaves here and there, it’s nothing to worry about, as the plants regularly renew their leaves by yellowing and dropping the old ones. However, if most of the leaves are yellow, or the plant looks wilted or stunted, it’s a sign that something’s not right.
Tropical hibiscus plants are very vulnerable to environmental changes. Bringing them indoors or out, repotting, and changes in their care can cause the plant to become stressed. Even minor changes that you might not notice can cause problems.
Sometimes yellowing of hibiscus leaves is a sign of temporary distress, and the plant will recover. At other times, it can be a sign of a more serious problem that must be addressed to save the plant.
Causes of Yellow Leaves on Hibiscus
Unfortunately, figuring out the cause of the yellowing leaves requires a bit of detective work, because it can come from lots of different causes. Here are some things to check on your hibiscus:
Water: Too much or too little water is a primary cause of yellowing hibiscus leaves. Tropical hibiscus need lots of water, but they don’t like to be soggy. Water more often (even daily) during heat waves, and less when it’s cool or overcast. Make sure the plant doesn’t sit in water and that the soil isn’t constantly wet.
Soil: Soil compaction, poor drainage, or lack of soil (becoming rootbound) are other causes of leaf yellowing in hibiscus, often because they contribute to water issues. Check the soil pH, and keep it slightly on the acidic side. Gently probe the soil around your plant, or lift it out of the pot, to see if the roots are packed and circling. If your hibiscus needs repotting, use a light, well-draining potting mix or soilless medium. Don’t plant in too big a pot, as hibiscus like to be just a wee bit crowded.
Temperature Changes: Moving your hibiscus, bringing it indoors, and normal weather changes (including wind) can cause temporary stress. Hibiscus need temperatures in the upper 60s to low 80s F. Exposure to extreme temperatures or drafts can cause the leaves to drop. If you’re growing your hibiscus indoors, keep it away from heat and air vents and drafty windows.
Light: Hibiscus are full-sun plants. Lack of sunlight can cause overall yellowing of the leaves. On the other hand, if the plant is getting sunburned, the leaves can get yellow or white splotches.
Insect Infestation: Spider mites and aphids are two major pests of hibiscus that can cause leaf damage and discoloration. Look for spider mites on the underside of leaves, and aphids clustering near the tips.
Nutrition Problems: Overfertilizing is another common cause of leaf yellowing in hibiscus, because of the shock it causes to the plant. Feed plants lightly and regularly, rather than heavily. I found some sources recommending occasionally supplementing your hibiscus with a very weak vinegar solution to lower the pH. I’ve never tried this but it could be helpful if your water is alkaline. Extremely poor soil can also cause hibiscus leaf yellowing due to nutrient deficiency. If the leaves are turning yellow with green veins, a condition called chlorosis, it’s a sign of nutrient (usually mineral) deficiency.
Chemical Shock: Pesticides can also cause leaf yellowing in hibiscus, especially if applied too heavily or during the heat of the day. Use organic pest control products, such as insecticidal soaps, and follow package instructions exactly.
Dormancy: Tropical hibiscus often goes through a dormancy stage during the winter. When you bring your plant indoors in the fall, it will likely lose some leaves due to the seasonal and environmental changes.
How to Care for Hibiscus
Once you’ve sleuthed out the cause of the problem, here are some tips for getting your plant back on track:
Correct Problem: It probably goes without saying, but the first thing to do is change the conditions causing the problem! Water, repot, move, or protect your hibiscus plant to keep the growing conditions as stable as possible.
Pruning: Once you’ve corrected the problem, your hibiscus plant should begin to sprout new leaves, but you may want to trim back bare branches to reduce water and nutrient needs as your plant recovers.
Be Patient: Plant problems can be difficult to diagnose and often take trial and error to correct. Once you hit upon the right solution, your hibiscus plant should recover nicely.