Common reasons why leaves turn yellow on hibiscus, and what you can do to revive the hibiscus plant. Find out here.
1. Cold Weather / Temperature Changes
The most common reason for leaves turning yellow on hibiscus is a drop in temperature. As hibiscus is a tropical plant, it does not like temperature under 50° F (10° C). Under such conditions, it will go into dormancy and some of its leaves may turn yellow and fall off. This is a natural process and there is nothing to worry about it. As long as the temperature remains above 35°F (2°C), the plant will stay alive, and healthy. It just stops growth of new shoots.
During early spring, the plant will come out of dormancy. But before that happens, you may see another wave of yellowing and dropping of leaves. You will also see new shoots grow at the same time. So, it’s less worrisome during this time.
What You Can Do: If you have planted hibiscus in a pot, you should move it indoor when night temperature drops under 50° F (10° C) and allow it to stay dormant during winters. Water it occasionally only after the topsoil of pot has dried out. Bring Hibiscus outdoor in early spring. Avoid fertilizing Hibiscus until spring.
2. Iron Chlorosis
If the leaves and flowers of your Hibiscus plant are getting really pale, then it could be a symptom of iron chlorosis. This means that your plant is not getting the supply of iron, it needs for healthy growth. Now, this can happen due to a variety of reasons like over watering, or lack of iron in the soil, or PH imbalances or due to some of these reasons. We have written about these problems separately below.
What You Can Do: While it’s important to find out the exact cause of chlorosis; it is equally important to provide iron to the plant immediately. Treat with chelated iron fertilizer spray for a quick fix and a 2 weeks later add some chelated iron around the root system for long lasting results.
3. Under Watering
Hibiscus is native to hot and rainy climate. So, they prefer a consistently moist soil. If you don’t water them frequently, especially during summers, they can go into drought stress and drop leaves and buds. Such a situation can also happen if you have used sandy or rocky soil that drains too quickly.
What You Can Do: Make sure that you water Hibiscus as soon as the top layer of soil goes dry. If required, water them two times a day during summers. If you have used sandy soil in pot that drains quickly, then replace it with garden soil rich in organic matter and compost. A layer of mulch at the base of plant can also help retain soil moisture.
4. Over Watering
Just like under watering, over watering can also result in yellowing of leaves in Hibiscus plant. When hibiscus pots are saturated with water, it deprives the roots of oxygen. After a while, this lack of oxygen causes the roots to suffocate and the leaves to yellow. It can lead to root rot and plant death as well.
Too much water can also keep a plant from being able to use micronutrients and iron available in the soil/potting medium.
Over watering issues are more common in potted hibiscus plants than those that are planted outdoors in the garden. This is usually the result of improper watering or poor drainage.
What You Can Do: Make sure that the soil used in hibiscus pots is not rich in clay and drains well, while remaining rich in organic matter. Avoid containers with no drainage holes. While Hibiscus love water in summers, we must avoid watering too much and too often. Water only after the topsoil has gone dry. Reduce the watering frequency during rainy season and the dormancy period in winters.
5. Pest Attack
Pest attacks are quite common on Hibiscus. Usually, the pests are clearly visible, and all you need to do is to spray an insecticidal soap solution.
But sometimes pests, especially the mites are not easily visible. All you see is yellowing leaves of Hibiscus, and may be a few curling or not fully open leaves at the top of the shoots. Sometimes, hibiscus bud drop also results from such pest attacks.
In such cases, many people think the plant is having nutrition deficiency or temperature stress but they actually are suffering from mites or other invisible pests.
So, its always a good idea to spray a pesticide whenever you see yellowing and curling leaves.
What You Can Do: Apply an organic pesticide. Sometimes, it does not work. In such cases use a strong pesticide like Bonide Pyrethrin to rid the plant of pests.
6. Overuse of Pesticides
When you see a heavy infestation of pests like aphids, stick to the usual dosage of insecticide. More insects do not mean that you need more concentrated insecticide. In many cases, overdose of insecticide can cause yellowing and dropping of leaves.
What You Can Do: Once you have sprayed the highly concentrated pesticide, there is nothing you can do. Just wait, and the plant will recover by itself.
7. Too Little Sunlight
Hibiscuses are native to the tropics and flower to their best in full sun. If you have planted Hibiscus in an area that received less than 3 hours of direct sunlight, then you will notice that the plant is not growing well, and the leaves are turning yellow due to lack of chlorophyll.
What You Can Do: Move the plant to an area that gets 5 or more hours of direct sunlight. With more light the leaves can recover from their yellow appearance.
8. Too Much Heat with Low Humidity
Hot and dry weather combined with windy conditions is a problem for Hibiscus. Such weather conditions cause Hibiscus to drop off its leaves as a survival strategy to prevent it from losing too much moisture.
What You Can Do: Increase watering frequency in case of hibiscus planted in ground. Adding a layer of mulch to the soil around your hibiscus is beneficial. Misting the leaves also helps.
For potted hibiscus, move them indoors, where they get 3+ hours of morning or evening sunlight. Protect from air conditioning or other sources of heat that can create convection currents around the house. If moving the plants indoor is not possible, then use sunblock green net.
9. Nutrient Deficiencies
Hibiscus is a heavy feeder, that needs to be fertilized often. The frequency of fertilization can be reduced by using slow-release organic fertilizers like worm castings. Such fertilizers are not only safe, but they also include trace elements, like iron, copper and boron. Occasionally, you may use a low phosphate fertilizer to produce better quality blooms.
In rare cases, a plant might be unable to access nutrients for other reasons, like pH imbalance. Such a situation can hamper nutrient absorption. If the problem is pH-related, adding fertilizer may not help.
What You Can Do: Hibiscus likes neutral to slightly acidic soil between 6.2 to 6.8 PH. You can test it using a soil pH meter. If your soil is out of this range, then you can modify it by using sulfur to lower soil PH or by using lime to increase PH.
10. Over Fertilization
Like with every plant, we must be very careful about appropriate dosage of chemical/non-organic fertilizers. At high dosage, these fertilizers may burn the leaves of Hibiscus. In some cases, the plant may even die. If you have applied chemical fertilizers recently and you see yellowing of Hibiscus leaves, then you can assume that it happened due to over fertilization.
What You Can Do: In such a situation, you can remove the soil around affected Hibiscus, and replace it with fresh soil. Water sufficiently.
11. Phosphorus Rich Fertilizers
Hibiscus needs very little amount of phosphorus, and fertilizers like bone meal, DAP, bloom boosters, etc can harm it. When phosphorous builds up in the soil it prevents the hibiscus to absorb other nutrients, causing a nutrient deficiency that cannot be fixed with more fertilizer.
If you have no option but to use chemical fertilizers, stick to a balanced fertilizer with equal parts of Nitrogen, Phosphorous and Potassium (NPK). Otherwise, the best choice of fertilizer for earthworm castings, leaf mold and well-rotted manure.
What You Can Do: If you have already used a phosphorus rich fertilizer, and you are seeing slow growth or yellowing of leaves, then you should replace the soil around Hibiscus plant with soil that is amended with organic matter (compost).
12. Compacted Roots
Yellow leaves on a potted hibiscus might be a sign to check for compacted roots. If the hibiscus has been in the same pot for a long time, the plant becomes root bound and the soil gets exhaust of nutrients. This results in yellowing of leaves due to nutrient deficiency.
What You Can Do: Repotting the hibiscus using soil rich in organic matter will fix this problem.
13. Transplant Shock
If you repot a Hibiscus or simply move the pot from one area to another or move the pot indoors then the change in conditions can turn the hibiscus leaves yellow due to stress.
To revive hibiscus, simply recreate the conditions in which they thrive in their natural habitat. Place it in full sun, provide it with well-draining yet moist & nutrient soil and protect from pests & excessive winds. Happy Gardening!