In the Garden with Pat Rubin

Bee garden writer Pat Rubin writes about everything that grows, from flowers and trees to vegetables and lawns. Pat volunteered for several years as a Placer County Master Gardener and has written about gardening for many national and regional publications. In addition to gardening, she spends time raising and showing miniature horses and miniature donkeys.

In the Garden will include news, events, advice and other gardening tidbits. Pat will also answer reader questions.

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January 22, 2008

Frost versus tropical hibiscus

Q: For several years, I've planted tropical hibiscus in pots around our swimming pool. At first, I tried to over-winter them, but had little success, so I started pulling them up and buying new ones each year. Last summer the ones I picked turned out great. They were full of blooms all summer. I kept them and am going to try to get them to come back. In the past when I tried this, they were very slow to leaf out and bloomed very late. Any suggestions on how to encourage them to bloom earlier?
Gary Schackner, Rocklin

A: The key point to remember is that these plants are tropical, and a long way from home. Even though our winters are mild compared to much of the rest of the country, your hibiscus will need some protection and coddling in our climate.

I’d take a two-prong approach.

First, I’d take cuttings late fall or early summer, and keep the new young plants in pots in a protected area. That way if you do lose the potted plants, you'll have new ones in reserve. Cuttings should be four to six inches long. Use branch tips that are mature, but neither soft nor hard and woody. Insert cuttings in a coarse potting soil,and keep them moist. They should root in six or eight weeks.

Next, come winter, I’d take every precaution to protect the mother plants.
Use anti-transpirant sprays (available at nurseries and garden centers) like Cloud Cover or Wilt-Pruf. Wind and frost can cause plants to loose moisture, which can lead to an untimely death. The sprays act like a protective coating on the leaves and reduce water loss.

There are frost blankets on the market today that let light in and you can leave on the plants without harming them. They can even be touching the foliage without damaging it during freezing weather, unlike plastic. You could also string some large-bulb Christmas lights through the plants to give them extra warmth on chilly nights. When frost is predicted, switch on the lights.

They can be slow to start in the spring, says Don Shor, owner of Redwood Barn Nursery in Davis. He recommends cutting the dead or damage growth back when new growth appears in spring, and repotting the plants at the same time. The "cross your fingers," he says.

Shor had a customer with a similar problem who used the above-mentioned precautions to save a row of tropical hibiscus, and for about $25 each winter was able to save $200 worth of plants.

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