I live near the coast in Los Angeles County, CA. I planted a one-gallon hibiscus about three months ago and it seemed to be doing fine.The weather has started to warm and the leaves are no longer dark green. They're a yellowish green with some of the older leaves becoming yellow along the edges. It has some new growth and a few flowers. I suspected the problem is over-watering due to heavy rain but the soil has dried out and things haven't improved. What's wrong?
Hibiscus Pink Versicolor
Certified GKH Gardening Expert
Unfortunately yellow leaves can be a sign of any number of problems. Overwatering is always a prime suspect, so you're right to be thinking that way. How long has it been since the heavy rain? The plant might just need more time to recover. Another common culprit is nutrient deficiency. If you haven't fed your hibiscus yet this spring, try doing so now. That should help if it's lacking in nutrients, and if it's trying to recover from waterlogged roots, it can't hurt either. This article goes into more depth about how to fertilize a hibiscus: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-fertilizing.htm
There are a few other possible causes, and this article covers them all: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/answers-to-what-causes-hibiscus-leaves-turning-yellow.htm