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Friday - June 10, 2011

From: White Oak, TX
Region: Southwest
Topic: Non-Natives
Title: Problems with non-native althea in White Oak TX
Answered by: Barbara Medford

QUESTION:

I have an althea bush that is 2 years old. I have never had a problem with it before but this year only half of it has leaved out and is blooming. The other half has some very small leaves and very small blooms but will not bloom or continue to leaf out. I tried putting some fertilizer on it to help the problem and discovered that ants had made a home in that side of the bush actually in the branches and the roots. Is there any way that I can save it?

ANSWER:

Hibiscus syriacus, Rose of Sharon, formerly referred to as Althaea syriacus, is native to India and China and therefore falls out of our realm of expertise. The Lady Bird Johnson Wildflower Center is committed to the growth, protection and propagation of plants native not only to North America but to the areas in which those plants grow natively. We realize you probably bought the plant locally, but the fact that a plant is sold locally does not mean that is native there or even, in some cases, will survive at all.

There are a number of problems that this plant can have, including leaf spots, cankers, rust, aphids and spider mites. Putting fertilizer on an already stressed plant is never a good idea-the fertilizer pushes the plant to put on new growth when it is just struggling to survive. Also, the fertilizer will encourage  production of leaves, at the expense of blooms. Using a high-nitrogen fertilizer, such as a lawn fertilizer, will only discourage blooms.

We don't believe the ants are your primary problem. Please read this previous Mr. Smarty Plants question involving ants, which turned out to be an aphid problem. An excerpt from that answer:

Ants are farmers and very fond of aphids, but not to eat. They will protect or fiercely defend aphids so they can harvest the "honeydew," exuded by the aphids. That honeydew is a major food source for the ants. On outdoor (and sometimes indoor) plants, ants protect and care for honeydew-producing insects such as aphids, soft scales, whiteflies, and mealybugs, increasing damage from these pests.

What to do about it? Since your plant is non-native to North America we have no information on it in our Native Plant Database. If you eliminate the aphids, the ants will move on to somewhere else they can practice their honeydew farming.   We recommend a good hard spray of water onto the affected plants, which knocks aphids and their eggs off and they can't get back up. The next thing you can do is try to keep the aphids from wintering over in your garden. See this aricle on Controlling Aphids in Your Garden.

If you don't find indications of aphids on your plant, search on the Internet for the other problems that Hibiscus syriacus is known to have and are listed above.

 

 
 

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