1 - If you want to grow blueberries in New Mexico, you must work to modify soil pH.
Q. You recently wrote about growing blueberries in New Mexico. I thought gardeners were discouraged from growing blueberries because of the nature of our soil. What has changed?
A. Actually nothing has changed. Blueberries require a very acidic soil to grow properly. New Mexico provides an alkaline soil in which blueberries grow poorly and for only a short time. Dr. Walser, NMSU Extension Urban Small Farm Specialist, successfully grows blueberries by acidifying his irrigation water to a pH between 4.5 and 5.5. (The pH is a measure of acidity and alkalinity.) In some New Mexico soils, it is possible to grow blueberries if acidified water is used each time the blueberries are irrigated.
According to Dr. Walser, commercial growers of small fruits, including blueberries, have secure sites and specialized equipment that allow them to acidify their water with concentrated acids. Dr. Walser does not recommend this method for homeowners. Acids used by commercial growers are very caustic and too dangerous to recommend where specialized equipment and proper protective clothing (including eye protection) are not available and people are not trained to use them. In home situations, the commercial solution to growing blueberries is dangerous for children and pets as well.
Dr. Walser says that home gardeners willing to invest the effort and money can, however, use safer methods to grow blueberries. The first possibility for home gardeners is to grow dwarf blueberry varieties in containers in which the soil pH may be more easily maintained at a low pH. The soil should be based on peat and contain a mixture of pine bark, other acid-forming organic matter, and sulfur. Over time, the soil may accumulate minerals from the water that reduce the soils acidity. At that time the blueberries should be repotted in acid potting soil. The soil will maintain its acidity longer if the plants are irrigated with water to which vinegar has been added.
Gardeners wishing to grow blueberries in their garden (not in containers) should modify the soil by adding quantities of fine pine bark and other acidifying organic material. They should mulch with pine needles or other material that acidifies the soil as it decomposes and they should irrigate with water acidified by the addition of vinegar to their water. This vinegar can be added by an injector that adds the proper quantity of vinegar to the water as it flows through the irrigation lines. Such injectors are available in a variety of types through some gardening supply catalogs and on the internet. To assure the water is properly acidified, the gardener will need to purchase a pH meter to measure the pH of the water as it leaves the drip emitters in the irrigation system (not at the point it enters the system, but at the point of delivery to the plants). At this point, the water pH should be between 4.5 and 5.5. In some parts of New Mexico, the buffering capacity of the soil may prevent the growing of blueberries even if the water is acidified.
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: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!