Issue: April 12, 2002

Landscaping septic field

I have a septic system in my back yard. I would like to plant some trees and shrubs. Can you give me a list of trees and shrubs that produce shallow roots so as not to affect my septic system? Please include native plants and trees in your list. Gregory M. Rio Rancho

This is a common question that should be considered when septic systems are near plantings. There are "infiltrator systems," which may not be affected by plants, but the septic systems with a septic tank and leach lines may have problems. The primary problem is having roots enter the leach lines, clogging the lines. Planting above or near the septic tank may not cause a problem from the roots of the plants because this is a closed system that roots cannot easily enter. The problem with planting near the tank is that the septic tank is often near the surface, and the soil above it is not sufficient for plants other than grass. Also, it would not be wise to plant something that would interfere with the clean-out access to the tank. There are almost no trees and shrubs that can be planted over a septic leach field without risk of clogging the system. There is too great a chance that their roots will invade the leach lines. If the leach lines are clogged, you will find it necessary to dig up the system and replace it, killing the trees and costing a lot of money. Wildflowers, grasses, and other herbaceous plants are a better choice than trees and shrubs. Natives are good because you don't want to water an area in which the object is to dispose of septic system water. Native grasses, especially ornamental bunch grasses such as little bluestem, sheep fescue, blue avena, miscanthus species, and giant sacaton (quite tall), will be helpful in extracting the water without clogging the system. These may mix well with wildflower plants such as lupines, Indian paintbrush, Mexican hat, gloriosa daisies, butterfly weed (not really a weed), Russian sage, and many others.>

Redbud propagation by cutting

A friend brought me a branch from her Redbud tree and told me I could grow a tree from the branch. The end of the branch was fresh and in water. What next? Cecily R.

According to some plant propagation texts, this is a procedure with a good chance of success when cuttings are rooted in the late spring and early summer. Treat the base of the cutting with some rooting hormone (not considered essential) and then place the cutting in a pot of good potting soil. If the cutting is kept in a humid location to prevent desiccation, roots should form in a month or so. In New Mexico, a cold frame or clear plastic bag (not in direct sunlight) will help maintain the needed humidity. Once roots have developed, it may be planted in the landscape.

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!