Issue: July 15, 2000

• Don't put barbecue ashes in garden in New Mexico
• Mossy things growing on trees in New Mexico

Don't put barbecue ashes in garden in New Mexico

Would the burnt dust from a charcoal barbecue help enrich the soil in my garden and, if so, how much of the dust would be beneficial? It seems like a good way to recycle my barbecue refuse.
Josh New Mexico

The usual answer to questions about using wood ash to enrich soil in New Mexico is -- DON'T DO IT! Now, if you are in the mountains and have a low pH soil (rare even in the mountains in New Mexico), it is possible to use the wood ashes, but very carefully).

Wood ashes contain a lot of salt. The organic material has oxidized (burned off) leaving behind a lot of minerals, especially potassium. This material increases the salt content of our already salty New Mexico soils. To make the situation worse, most New Mexico soils are not deficient in potassium, so we are creating a problem without gaining any benefit. We recommend that the wood ashes be disposed in a manner that does not add them to garden soil (in a landfill or spread over a gravel driveway, etc.). Do not even add them to the compost pile.

The only way to be certain that the above warning applies to your soil is to have your soil tested. Look especially at the pH results and saltiness. If your soil is acid, then you can use the wood ashes in the garden.

In other parts of the country, especially east of the Mississippi River (and some areas to the west), the soils are acidic and deficient in potassium. In these areas, the addition of wood ashes is beneficial. It is from garden books written for these areas that we will find recommendations to add wood ashes to the garden.

Mossy things growing on trees in New Mexico

I have an interest in property in Colfax County (Angel Fire area) and now notice that the pine trees there appear very distressed this year. Many branches and some entire pine trees are dead. Long-needle and short-needle pine are both attacked by a stringy moss-looking parasite. The long-needle pines seem to be the worst affected. Fir, aspen and blue spruce do not appear to be significantly affected. My questions are (1) What is the name of the parasite in question? (2) Does it only attack pines? Others? (3) What is normally the ultimate outcome of an affected tree? Is it fatal? (4) What can be done about the parasite? Spray? Systemic treatment? (5) Any recommended product to use for treatment?

The organism you asked about (calling it a parasite) is in actuality a lichen, a symbiotic association of fungus and algae. It is not a parasite. That is, it does not take its nutrition from its host tree. It only sits upon the tree. There are lichens which grow on rocks, fence posts, and even telephone lines which provide no nutrition, only a substrate on which to sit.

The stress evident in the trees is probably drought related. The winter was much drier than normal and the strong winds in much of New Mexico have made the drought stress worse. Trees which are defoliated or partially defoliated by stress become the best places for the lichen to grow as more light is available. So there is a relationship between the condition of the tree and the growth of lichen, but the lichen do not cause the problem.

A concern however, is that lichen is very flammable, so if a fire went through the area, the trees with lichen would be more susceptible to ignition. In the absence of fire, the trees may continue to decline if the drought persists and if the damage done by drought is irreversible. If more water was provided to the trees, some may recover and return to a normal appearance.

There is no real treatment for lichen and no really good reason to try to control it. If you must try something, try a diluted solution of copper sulfate. Copper sulfate will kill the fungus and algae, but it can also damage the tree. So, be warned that there is the potential to do more harm than good.

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.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!