Flood Hibiscus With Full, Hot Sun, Not Water
QUESTION: Do some hibiscus lose their leaves in winter? This is the second time I’ve planted ‘Kona’ hibiscus, and it is losing its leaves.
--R.C., Los Angeles
ANSWER: Although there is a deciduous hibiscus called Rose of Sharon, Hibiscus syriacus, that’s not what you’re growing. The tropical hibiscus (H. rosa-sinensis)--grown all over the Southland--should not be losing its leaves, though some leaf drop is typical in winter. Without seeing the plant, it is difficult to tell what the problem is, but the two most likely causes are too much shade and too much water.
Hibiscus want full, hot sun, good drainage and moderate water. If the plant is in a chilly, shaded spot it will loose leaves, and if the soil is cool and damp all the time, ditto. Sounds like it is planted in a bad spot or in a heavy clay soil.
According to one grower, you could also be jumping the gun. Apparently young hibiscus may “falter” in cooler weather, especially in heavy, wet soils where their roots are not getting enough oxygen, and the leaves will defoliate from the inside of the plant out. Don’t be too hasty to take the plant out; instead, wait and see if it adjusts to its new home with time. Hibiscus are one of our more reliable flowering shrubs.
How to Prevent Plants From Turning Brown
Q: We have Erodium chamaedryoides and E. corsicum planted as ground cover among azaleas on the north-facing front of our house, where they are watered every day. All of a sudden some began turning brown and dying off. We are having similar problems with Geraldton waxflowers at the top of a sunny hill. Can you offer some suggestions for remedial action?
--D.D., Fullerton
A: This sounds like a similar problem. Erodiums or cranesbills--little relatives of the true geraniums--don’t like heavy clay soils, and that goes double if they are getting too much water. I would say that watering them every day is irrigating way too much. They also prefer sun over shade, though they can tolerate a little.
But the real problem is the daily watering, even though Fullerton is a hot climate. At most, these plants should be watered twice a week in summer, less at other times of the year. You should be watering way less.
Since frequent watering encourages shallow rooting, the plants can’t be changed over to a less frequent watering schedule all at once. They need time to grow their roots deeper. If you start reducing now, you can have them weaned from frequent watering by late spring. Next summer, try watering for a longer period each time, but less often.
You can try replanting any you lost over the summer at this time of the year, though it sounds like the cranesbills may not be getting enough sun. One of the reasons to plant things in the fall is to get them accustomed to their new home at a less stressful time of year (for plants anyway).
During the winter, they’ll send their roots deep into the soil. By spring and summer, they should need infrequent watering, especially the waxflower. Watering as often as you are, you are bound to kill plants with kindness; the crown and roots will rot and the plants will quickly die or they will turn yellow, wilt and then die (which can look as if they were not getting enough water).
Back off and you may be surprised how well these plants do. They’re really quite tough.
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