When desert species such as Mesquite, Acacia and Palo Verde are planted in irrigated landscapes, these trees respond with lush, rapid growth. This can become problematic when these trees are planted in locations with space limitations. Frequent pruning is required to maintain size and prevent interference with structures and sidewalks. Additionally, rapid growth can lead to structural issues. Because irrigation is often applied only to a limited area of the root zone, a large root system may not develop to structurally support the plant. Extra care will be needed in the form of routine pruning to maintain root-crown ratios and reduce the potential of trees toppling in windstorms.
Recently, tree growth regulators have been developed to slow the growth of woody plants. Applied to the soil immediately adjacent to the stem, the growth regulator is absorbed and translocated throughout the crown. Growth regulators act on cell elongation so new shoots expand less than untreated plants. While the products don’t stop growth, they do slow growth significantly for a period of approximately two years. In addition, treated plants demand less water because of the growth regulation.
January is an ideal time to apply tree growth regulators. The product will be absorbed over the winter months and begin regulating growth in spring when trees flush out. Growth regulators can be applied at other times of the year as well but expect a one to two month delay in the onset of regulation due to the time required for absorption and distribution in the tree.