The recommended time to prune desert adapted trees is during summer. You should not prune mesquite trees for at least one year after planting, and preferably two years except for dead or damaged branches and branches that will cause problems in the future.
Because mesquite trees grow faster in the warmer periods of the year, they need some special attention. Newly planted trees should have drip emitters placed fairly close to the trunk supplying water to the tree while the roots are in a restricted soil area after planting. Two lodge poles can be used to support single trunk 15 gallon and 24″ box-sized trees.
Drip Emitter Use
These practices will be sufficient when the tree is first planted, but as it grows, any drip emitters should be moved away from the trunk to the “drip” line. (The “drip line” is the edge of the canopy, or where the branches end.)
Moving the emitters out will promote the roots to grow outward into the surrounding soil and away from the trunk. This will assist the mesquite tree in establishing itself and provide support by creating balance between the root system and the canopy of the tree. Also, this will allow the area immediately adjacent to the trunk to dry out and become more solid, thus providing a little more support against the wind.
Pruning is also important for young trees. The extensive canopy of your mesquite tree should be thinned occasionally by pruning some of the inner branches. The most important branches to remove are those that cross and/or touch one another branch inside the tree’s canopy. Removing those branches will allow the wind to pass through, thus helping to avoid broken branches or the tree getting blown over in a storm. Proper thinning will not only help avoid wind damage, but will also aid in proper branch structure.
Wind damage and uprooting are the products of poor pruning and staking practices and improper irrigation and should not be considered as inherent, unavoidable horticultural shortcomings. Making trees seek out water and nutrients, by appropriate arrangement of irrigation emitters, fosters the development of a more dispersed root system and reduces the risk of wind throw.
Pruning to remove about 20% of the canopy every 3 to 4 weeks during the growing season helps promote root development that is proportional to the shoot growth of young trees. Removing more than 20% of the canopy can inhibit rooting and encourage undesired re-growth made up of dense flushes of branches and leaves.
Selective pruning should be used to foster the development of a symmetrical canopy with well spaced branches. Stake trees only when absolutely necessary and then only briefly. A low-breaking, upright tree occupies no more room than a standard-trunked specimen yet retains the natural wind resistance of trees found growing native in desert settings.