Burned Crape Myrtle Plants

Question:

I have 20 crape myrtle plants that are looking burned and crispy. They are planted with a block wall to the north and white rockscape around them. I think the problem is sunburn from the wall and rocks and the fact that the planting faces south to southwest.

What other plants would work well under these conditions?

Answer:

Crape myrtle will grow in southern New Mexico and as far north as Albuquerque, but the dry air and our soils can create some problems. It is likely that the dissolved solids are high in the water and soil. High temperatures and dry air make the problem worse. As the crape myrtle plants shade the wall, they will partly remedy the problem by reducing heating from the direct sunlight falling on the wall. A living mulch over the rocks (vinca or other vining plant) will also help lower the temperature around the crape myrtle plants.

Calcium salts from the wall (and perhaps from the rocks) contribute to the salt problems. If the water has high levels of salt, especially sodium salts, it will be a major contributor to the problem. A soil and tap water test will help determine if this is the problem and if the water can be used to remedy the problem.

If the water is not too salty, it can be used to leach salts from the soil. Harvested precipitation water is the best water for leaching the salts. Adequate water applied often enough to keep the soil from drying completely during the growing season will also help.

Another option is to remove the rocks several feet from the base of the plants and replace it with organic mulch (bark or wood chips). Organic mulches will create a cooler environment around the plants and help conserve water in the soil. They will also help as they decompose and acidify the soil, speeding the leaching of salts.

Replacing the crape myrtle plants is another option. If you wish to keep the crape myrtle plants, move them to a more humid and less sunny location. Replacement plants may include desert willow, Mexican bird-of-paradise, fernbush, native mahonia and other native or locally adapted shrubs. Vines to cover the wall may also be considered. These include trumpet vine and silver-lace vine.

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Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

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