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Index : Trees
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- 3. October Is Tree Planting Time - Top
- Without a doubt, October is the best month to plant trees here in the desert Southwest. Cooling autumn temperatures make it less likely that leaves and stems of newly planted trees will shock and dry out. In addition, still warm desert soils encourage the growth of new roots vital to the establishment of young trees.
When purchasing a tree from your favorite local garden center or nursery, make the right choice. Selecting a tree that will eventually outgrow it’s allocated space leads to inevitable problems. Look for a tree with a slight taper to the trunk; larger at the bottom and smaller at the top. This is a sign of good trunk development. Also pick one that has branches spaced all along the trunk, even down low. Low branches help increase the girth and strength of the trunk.
When planting, dig the hole just deep enough to fit the root ball into the ground, with the top roots level with the surrounding soil surface. Dig the hole one or two feet wider than the root ball to provide space for new roots to grow. Fill around the tree roots with the soil you dug from the hole, taking care to remove any large rocks. Do not add organic amendments such as compost, topsoil or manure to the planting hole. New roots must adapt to growing in our native desert soils. Forming a planting hole with enriched soil restricts root growth by creating a pot-in-the-ground that roots can’t grow beyond.
To help direct water down to the roots and prevent run-off, form an irrigation well around the tree. This is made by mounding up soil up a few inches high in a circle at the outside edge of the tree’s root ball. The ring of raised soil will help hold irrigation water until it absorbs into the roots and surrounding soil.
After planting, make sure the tree is watered often enough to keep the soil moist. Warm weather may necessitate daily watering for the first week or two. As temperatures cool, gradually lengthen the intervals between watering.
Regardless of the type of tree you have planted, native desert or non-desert tree, they all need to be watered on a regular basis until they become established. This usually takes one complete growing season. Trees planted this fall, should be fully established by next fall. When established, native desert trees such as Palo Verde can be taken off irrigation entirely. Introduced tree species such as Live Oak, however, will require continued watering throughout their life.
Don’t prune any of the branches on the tree unless they’re broken or otherwise damaged. The more branches, the more leaves and it’s leaves that manufacture carbohydrates to feed root growth. If the tree has shoots or branches on the lower third of the trunk, leave these on for the first year after planting. It’s these lower shoots that help stimulate the growth and thickening of the trunk.
Whenever possible, avoid staking trees. Small trees seldom need support. The purpose of staking is to prevent the root ball from moving in the soil and tearing off emerging roots. Our heavy mineral soils are usually sufficient to anchor the root ball. Never stake the tree in a fashion that prevents the trunk from bending. The natural bending motion of the trunk is beneficial in developing something called “tension strength” in the trunk. If a tree must be staked, ask for instructions at the time of purchase.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
- Updated: October 8, 2006
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