Why are the leaves on my hibiscus turning yellow?

I bought a full grown hibicsus plant at the beginning of spring. It sits by my mailbox and gets almost full sun. It has done great the whole summer...beautiful endless blooms. Yesterday it was wilted a little so I watered it as normal. Today when I woke up almost a third of the leaves were yellow. Can anyone tell me what I did wrong;and how I can fix it before loosing the plant?

Why are the leaves on my hibiscus turning yellow?
Don't panic, yellow leaves on hibiscus are normal. They look like something is wrong, but they are usually just a warning, a call for help, and not a sign of impending death.





Hibiscus leaves turn yellow and drop from the plant due to stress. The stress can be of any type, and figuring out what kind of stress is the challenge for the gardener. We cannot tell you exactly what is wrong with the plant without knowing a lot more than you are likely to be able to tell us. YOU have to think about it, and when you are pretty sure you have determined the cause, then you can take action to relieve the stress on your hibiscus. This article is intended to help you figure it out what is wrong.





Stresses that can cause yellow leaves on hibiscus include:





1. Not Enough Water


In warm conditions hibiscus need a lot of water, even every day or more than once a day if it's really hot or windy. Self-watering pots can be an excellent way to avoid this type of stress. A watering system controlled by a timer is another way for gardens with large numbers of plants.





2. Too Much Water


Yes, hibiscus can also be given too much water when the weather is cool or overcast. Hibiscus like to be moist but not sopping wet and if they don't need the water due to cold or dark conditions then too much will stress the root system.





3. Too Hot


This is related to water but please take note on super hot summer days that hibiscus will need lots of water to keep all the big lush leaves well supplied. If they don't get enough they react by dropping leaves (that turn yellow first) so that they don't need as much water.





4. Too Cold


Hibiscus are tropical plants that thrive in the same temperatures that people like - 65 to 85F. Like us, they will survive, but they will not like temperatures down to freezing and up to 110F. If they get too cold or are placed in a cold drafty window, they can react with yellow leaves.





5. Too Much Direct Sunlight


Hibiscus like sunlight but just as most people like moderate amounts of it so do hibiscus. Too much sun places stress on hibiscus that are not used to it and they can react with yellow leaves or big white spots on leaves. The white spots are similar to sunburn on us. They won't kill the plant but will cause it to shed leaves.





6. Too Little Sunlight


Light is the source of life for plants such as hibiscus. If they do not get enough to support all the big lush leaves they will drop some of their leaves (which turn yellow first) so that they don't need to support so many. However, that means that there is less green chlorophyll left to support the needs of the rest of the plant so it may continue to decline until there are only a few leaves left on the plant.





7. Insects, Particularly Spider Mites


Spider mites are tiny spiders that look like little crabs under magnification. Usually you cannot see spider mites with the naked eye but do they ever leave a mark on hibiscus leaves! First you may see mottling of the leaves which begin to look dirty and then tired. The underside of leaves will show marks made when the mites suck the juices from the leaves. As the infestation gets worse you will see small spider webs under the leaves and at the top of stems. Leaves will yellow and fall off the plant and the entire plant will look stressed. If left untreated, spider mites can cause every leaf on the plant to fall. It takes hibiscus weeks to recover from a bad spider mite infestation so it is best to take action as soon as the signs are present. This can involve washing the entire plant in water or better yet, in water with horticultural oil and soap, such as our Clean Leaf Spray.





8. Too Windy


Most of us do not realize the stress that wind places on plants. Wind dries them out and the result is yellow leaves.





9. Improper Nutrition or pH


This is a different category and the yellow is a different yellow. The leaves will remain partly green and partly yellow when there is a nutrition problem. Leaves almost always fall off the plant after turning solid yellow. If they do not turn completely yellow nor fall off then it is likely that the problem is a lack of essential nutrients. This can be due to no fertilizer applied or due to a pH level of the soil that is too high or too low. The leaves do not turn a bright yellow all over if this is the case nor do they drop off. Such problems can be corrected by using fertilizer and/or amending the soil with substances that will neutralize the pH. Consult a nursery professional at a local garden center if this is the case.





10. Pesticide Use


This is not a common problem but overuse of pesticide or using the wrong pesticide or too strong a pesticide or spraying in the hot sun of mid day can also cause leaf problems. If you have applied pesticide recently this may be the problem but if you used the same type at the same strength and done so in morning or evening then it is most likely one of the other stress problems above.





Once you have reviewed all the possible problems and decided on a likely source of the stress the cure is to remove the stress. Sometimes it is already done, as when you have watered thoroughly after neglecting to do so during a heat wave. There is no saving the yellow leaves that WILL fall off but the good news is that hibiscus will quickly grow back new green leaves when the stress is removed. Sometimes it becomes necessary to prune back a stem that has lost all of its leaves except for a few at the top. Pruning causes a cascade of plant growth hormones to enter the bare stem and stimulates new growth on the remaining part of the stem after pruning. This is a final solution if all else fails but it is best to remove the cause of stress first and to feed and water the plant well since that may be all it will take to get new growth on your hibiscus.
Reply:You didn't say where you live - so I may not have all the info you need. I live where hibiscus grow outside all year long. It is not uncommon for them to drop some leaves this time of the year. Also hibiscus can drop leaves just because they feel like it. But it does sound like you may have let it dry out a little to much. But it may only to short term. If you live where its cold in the winter, I am not sure of the winter treatment.
Reply:THEY NEED ALOT OF WATER. I LIKE TO PUT THEM NEAR A SPOT WHERE WATER MIGHT SIT AFTER IT RAINS. I WOULD ALSO CHECK THE LEAVES FOR SOME KIND OF INSECT. SOME INSECTS ONLY SHOW UP AFTER DARK. SO, CHECK DURING THE DAY AND NIGHT.
Reply:Are you feeding the plant? MIracle grow can help here. Are you over watering or underwatering the plant. The soil should be damp, not wet or dry.
Reply:You may be like me....... I over water or underwater; seems I just can't get it right. So, I am ordering a 12" "soil probe." When you insert it into the soil, then twist it, gently withdraw it and then check to see if there is any soil on the stem thingy, that lets you know if it needs to be watered or not. This "soil probe" does not require a battery. You can go to http://soilsleuth.com/soil_sleuth.html to order one for $7.75. There is also a phone number if needed. Mine will be here in four days. The probe can be used in your flower beds or in house plants. I think everyone should have one of those gadgets; whether you have a green thumb or not.
Reply:If it wilts, the leaves that it doesn't need die. Keep it moist and give it some plant food.
Reply:'tis time for us to say goodbye to our hibiscus. It happens every fall as the nights turn cool. I'll be cutting all of mine down to the soil line the next day or so. I sure hate to see summer go, don't you all?