Expert Advice: Hibiscus Bud Drop

Q: I had a lot of buds on my hibiscus bush. But they fell off just before they bloomed, and the few that did bloom had black edges on them. What caused this? —Mary Peppers, Pasadena, TX

A: When hibiscus plants drop their buds, it’s usually a sign of stress. Figuring out the cause can be tricky, but there are a few likely reasons:

  • Though hibiscus plants love heat and humidity, temperatures over 95°F can stress them. Thinking they may be about to die, they drop their buds as a defense mechanism. Help your hibiscus keep its cool by providing consistently moist soil and some protection from afternoon heat.
  • Hibiscus hate being moved and will often drop their buds in protest. Once the plant has settled in again, the problem should disappear.
  • Over-fertilization, nutritional deficiencies and environmental factors, such as poor drainage, can cause bud drop.
  • Several insects can cause bud drop:
    Thrips - Hold an almost-open bud over a piece of plain white paper and flick it with your finger. If you see a sprinkling of little black flecks, they’re probably thrips. Liquid pyrethrum is an effective control.
    Mealybugs - Check the stems for their fuzzy white egg sacks; use alcohol-soaked cotton swabs to remove them.
    Hibiscus gall midge - This pest causes buds to turn yellow and drop. It lays its eggs inside the flower buds; as the larvae develop, their feeding causes the buds to drop. A hibiscus-safe liquid systemic insecticide is the best way to control this troublesome pest. — Kathleen LaLiberte, garden writer and industry consultant