Certified GKH Gardening Expert
Hibiscus are one of the types of plants that respond to dryness by dropping yellow leaves. Brown edges can be caused by a range of conditions, among them too little moisture, but it's not the first thing I would think of with hibiscus. The best way to find out if your plant is too wet or too dry is to examine the soil. dig into it with a long spoon, a moisture meter, or a wooden skewer to see how much moisture is down there. You might find it's too wet! The soil should feel cool and light, not dry, but with a little moisture in it, and then it's good to have more water. If you determine that it's not too wet, the next thing to investigate is the mineral content. Do you fertilize alot? If so, you may have a salt build up due to unused fertilizer. Leach the soil thoroughly (run several gallons of water through to wash away the salt), and repot with fresh soil if possible. Then again, if you don't fertilize at all, there's a possibility that mineral deficiency could be the problem. If you still see the problem after you've leached the soil (or fertilized), you might want to analyze the soil for pH and mineral levels. You can get a simple soil test in most plant stores. It's not super accurate, but it will give you a basic idea, and indicate corrective measures.