by David Pojmann
There are major differences between country trees and urban trees. Country trees grew up in a favorable environment, along with others of their species, and adjusted slowly over the years to the soil conditions, water availability and micro-climates. They may have competed and won over other species of trees and other plants as well. Urban trees generally grew up in a nursery where their environment was closely regulated with the goal of fast growth over durability, and their roots were in a container that allowed little expansion. When a tree is planted in an urban environment it has to contend with many factors not present in a forest, so it is very important to select the right tree for the conditions on your property, such as soil type, pH, soil compaction, and distance to structures. Roots need oxygen as well as water to do their job. Depriving them either will result is a stunted, weak tree.
You can cut and paste the link below to take you to a USDA analysis of Sandoval County soils. You can use the map there to find the soil types in your area; however, if you live in a development, there is a chance that the soils may have been imported from other regions of the county. An analysis of the soil in your own yard is the best way to avoid planting trees that are not suited to the specific environment. It is better to match a tree with the pH of the existing soil than to try to modify the pH to suit a particular type of tree. https://www.nrcs.usda.gov/Internet/FSE_MANUSCRIPTS/new_mexico/NM656/0/Sandoval%20NM.pdf
Amending the soil around the tree was often recommended in the past when planting a tree, but most arborists today say to dig a hole two to three times the diameter of the container or root ball, then open up the roots of the tree to reduce the chances of their eventually strangling the tree. Put the soil that was removed back around the tree. The topmost root of the tree should be at or up to two inches above the native soil line. Water frequently during the first few months to ensure that the soil remains moist, but not wet.
Mulching trees in New Mexico is essential to their growth and health. Remember that a tree in a forest grows up with natural mulch that has accumulated over many years from leaves, bark, etc. Your tree deserves your best effort to duplicate those conditions. Mulch helps to retain soil moisture and controls weeds around the tree’s roots. It also protects the trunk from damage from mowing equipment if the tree is in turf. Mulch also helps to prevent soil compaction over the roots, and it will improve the soil over time as it rots, and it also will protect the soil from erosion by rainwater, especially on slopes. As a tree grows, add more mulch, keeping the area inside the drip line of the tree covered.
Two inches of mulch is the minimum to use. Four inches is better. Mulch may be bark, nut shells, straw, shredded trees, or gravel. Organic mulch works best, but appearance is also important in a landscape. Avoid using shredded tires. Keep the mulch a few inches from the trunk of the tree.
When trees are established, they still need water, pruning, pest control and general maintenance. Keep in mind that roots grow throughout the year, so it is important to water them at least monthly after the leaves have fallen, then more frequently when they start to green up. The water needs to go to a foot deep. Water at the drip line, not the trunk for stronger roots. The result will be earlier greening and more lush foliage in the summer months. Enjoy the shade.