   Tree and Shrub Planting Guidelines - October 4, 2006 Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Fall is a good time to plant evergreen trees in the Verde Valley area. This includes trees such as pines, junipers, deodar and atlas cedars. Many evergreen and semi-deciduous shrubs also perform well when planted in fall. These includes native shrubs such as sugar sumac (Rhus ovata), manzanita, apache plume, mountain mahogany, and cliff rose. Moderate air temperatures and warm soil temperatures allow plants to establish new roots and acclimate to the site before winter. Regardless of planting season, using the proper planting method is critical to long-term success of trees and shrubs in landscapes. The new method is often called the “Improved Planting Standard” and it is based on a wide, shallow planting hole and using no soil amendments in the backfilled soil. Many people (including nurseries and landscapers) have been slow to adopt this new science, but peer-reviewed research has proven that the method I will describe below is superior to the outdated and inferior “deep hole – amended soil” planting method. The Improved Planting Standard is also recommended by the International Society of Arboriculture, the National Arbor Day Foundation, and the nationwide Cooperative Extension system. The Improved Planting Standard uses the following steps: 1) dig the planting hole only as deep as the root ball; 2) loosen the soil in an area three to five times as wide as the root ball; 3) the areas where the loosened soil meets the undisturbed soil should be rough and sloped (not glazed or vertical); 4) place the tree or shrub in the planting hole and backfill with non-amended, native soil; 5) mound soil to create an irrigation well just outside the original root ball; 6) place three inches of organic mulch on the soil surface but do not allow it to contact the trunk; 7) remove the original nursery stake; 8) install new planting stakes if necessary (if the tree falls over when the nursery stake is removed); and 9) irrigate the tree or shrub as necessary wetting the root ball and surrounding soil. The Improved Planting Standard is superior because it allows roots to become acclimated to native soil and grow beyond the planting hole. It also prevents the root ball from sinking below the surrounding grade causing the root crown to become buried. Soil should never cover the root crown because the bark that is formed above this point requires oxygen and prolonged exposure to moisture can lead to disease or decreased vigor. The nursery stake should always be removed because it prevents the tree from developing strength and taper. Wood strengthens in response to wind and its own weight. If a tree will not stand on it’s own after removing the nursery stake, install two wooden tree stakes on opposite sides of the tree. The stakes should be driven deep enough to hit undisturbed soil below the root ball. Use flexible tree ties and allow some movement while preventing damage to the trunk. Cut off the tops of the stakes to prevent damage to nearby branches. Staking should also prevent movement of the root ball allowing new roots to extend into the native soil. Shrubs and most small trees do not require staking. Pruning is not necessary after planting. Damaged limbs can pruned out, but do not prune undamaged material. At one time, it was thought that pruning was necessary to “balance” the top growth with the root ball. This is NOT recommended. In addition, there is no evidence that newly planted landscape trees and shrubs should be fertilized. Ornamental landscape plants should only be fertilized when they show signs of nutrient deficiency. I know that many readers have always planted trees and shrubs in a hole twice as deep and twice as wide as the root ball and backfilled the hole with soil mixed with lots of organic amendment. In essence, all you have done is “re-potted” the plant. Roots will be concentrated in the amended soil and are much less apt to extend into the native soil. For more information on planting and staking trees and shrubs, visit the Cooperative Extension office and ask for the publication: Planting Guidelines: Container Trees and Shrubs or download it from our web site at: ag.arizona.edu/pubs/garden/az1022.pdf. Dr. Ed Gilman of the University of Florida also has an excellent tree planting web site at: hort.ifas.ufl.edu/woody/planting/index.htm. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |