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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Wednesday - December 08, 2010

From: Utopia, TX
Region: Southwest
Topic: Compost and Mulch, Diseases and Disorders, Transplants
Title: Blackened leaves on purple sage in Utopia TX
Answered by: Barbara Medford

QUESTION:

I live in Utopia Texas and have a 5-ft. Texas Purple Sage that has developed a black appearance on the leaves. What is this and what can I do about it?

ANSWER:

There are a number of different plants, mostly in the genus Salvia, that have the common name "Purple Sage." However, judging from the height you indicated, we are guessing that what you have is Leucophyllum frutescens (Cenizo). Without seeing the plant, knowing where it is planted in your landscape or what the soil is, we can only hazard some guesses, and you can use your judgment deciding what might be the problem.

You can follow the plant link above to learn about the preferred growing conditions for this plant. The first thing we would emphasize is that it needs very good drainage in the soil. In the first few months it is in the ground, it needs some deep watering, which is done by sticking a hose down in the soil and letting water dribble slowly in. If water comes to the surface when this is done and does not quickly disappear, the drainage is inadequate. If we are correct about which plant you are referring to, it does, indeed, grow natively in Uvalde County, so the USDA Hardiness Zone is appropriate for it.

If the plant is being watered by a sprinkler system, and especially if the drainage is poor, there is likely not only the drowning roots to consider, but a sooty mold caused by wetting the leaves. Also, the plant needs to be in full sun, which we consider to be 6 hours or more of sun daily. It will survive in part shade, 2 to 6 hours of sun, but will not bloom as well and, again, be susceptible to fungus.

If you feel the drainage is the problem, we would suggest you consider re-planting the bush. This is the right time of year for doing this, while the plant is semi-dormant. Dig a fresh hole, moving into more sunlight, if necessary, and add a good compost or other organic material. This will both improve drainage and enhance the roots' ability to access nutrients in the soil. Do not fertilize! This particular plant does not need fertilizer and you should never fertilize any plant under stress. After the drainage is corrected, a period of deep watering should be all that is necessary. Once well-established, the Cenizo is very drought-resistant.

One other possibility we will mention concerning the black appearance. Examine your plant for aphids. They excrete a substance called honeydew, on which a sooty mold can appear. They will not harm a healthy plant, but the appearance is unattractive.

From our Native Plant Image Gallery:


Leucophyllum frutescens


Leucophyllum frutescens


Leucophyllum frutescens


Leucophyllum frutescens

 

 

 

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