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Saturday - May 30, 2009

From: Buda, TX
Region: Southwest
Topic: Compost and Mulch, Diseases and Disorders, Shrubs
Title: Problems with Green Cloud purple sage in Buda TX
Answered by: Barbara Medford

QUESTION:

I planted the "Green Cloud" variety of purple sage about 3 years ago. Yesterday, I noticed yellowish dots on the underside of the leaves of some plants. Is this harmful? The plants seem to be ok at this time, but I'd like to prevent any problems that might be brewing. I thought about the cotton root rot, but we have been in a drought.....not much water here (however,the area is heavily mulched).

ANSWER:

There are 5 plants in our Native Plant Database with the common name "purple sage;" however, only one of them, Leucophyllum frutescens (Texas barometer bush), is native to Texas, so we will assume that it the one you are asking about. The species of this plant usually has silvery green foliage; "Green Cloud" is a selection which has green leaves and pinkish flowers. Pictures of Green Cloud.

We investigated the possibility of cotton root rot, but understand that this plant is pretty resistant to it. Another thing causing yellowing on leaves is chlorosis, the lack of cholorophyll, which is usually the result of the plant roots being unable to access trace elements, especially iron, in the soil. The key to both these problems is the drainage for the plant. Cotton root rot, for instance, is prevalent in calcareous clay loam, where drainage is poor. Chlorosis can be precipitated by too little drainage as well. So, the first thing you want to do is check that water is not standing on the roots of your purple sage. If water in a shallow depression stands there for more than about 30 minutes, your drainage is poor. You need some compost in the dirt in which the sage is planted, or it should be in a raised bed. Pull some of that mulch back, and work some decomposed matter into the soil as much as possible without damaging the roots. Let the lower branches get some air. Try gradually getting the air circulation improved and getting organic material into the soil, and see if that helps.