If you notice that your hibiscus leaves are turning yellow, you may be at a loss for what to do. Luckily, yellow leaves are not the end of the world. Rather, they are an indication that the plant has some need that is not being met. When you satisfy that need, the leaves will turn a healthy green again. The solution is to figure out what it is that the plant lacks and then to right the situation.
One of the most common causes of yellowness in hibiscus leaves is too much or too little water. The key to solving this problem is taking other conditions, such as temperature, into consideration when deciding how much water to give your hibiscus. During warm weather, hibiscus plants need to be watered daily or even on some occasions twice in one day, if it is particularly hot or windy. When the temperature is cooler or if it is cloudy, your hibiscus does not need as much water. Also, when the plant is dormant, you need only water enough to keep the soil from becoming completely dry.
Too much or too little light can be another cause of yellow leaves. If the plant is not getting enough light, the leaves will droop and become yellow, eventually falling. If the plant gets too much sunlight, this can cause yellowness in the leaves, as well as large white spots, which are the hibiscus' equivalent to sunburn in humans.
If the leaves remain partially green and do not eventually fall of the branches, the problem is most likely one of nutrition. One of two things could be wrong. Either the pH of the soil is not suitable for the hibiscus, in which case you should add substances to change the pH of the soil, or the plant needs more fertilizer than it is getting.
There are several other sources of yellow leaves. Hibiscus plants like temperatures between 65 and 85 degrees. A little cooler or a little warmer is fine, but extreme temperatures can cause leaves to turn yellow. Spider mites present another potential problem. These pests suck the juices from the leaves. To get rid of them, you'll need to spray the plants forcefully with your hose every 5 to 7 days, repeating the process 3 to 4 times.