The competing and divergent biological and physical need of trees and turf make the care and maintenance of trees planted in turf areas especially challenging. These challenges are amplified with certain desert adapted species and overwhelming with others. Landscape designs that attempt to create park-like environments by combining desert adapted species (and certain more traditional tree species) with turf, leave landscape maintenance professionals with the difficult task of satisfying the vastly divergent horticultural requirements of these two landscape elements.

The primary dilemma is will the trees tolerate the shallow frequent watering necessary to keep turf attractive and vigorous. Conversely, will the maturing tree generate shade that inhibits the growth, density and durability of turf. 

Summer Lawns: Mesquites and many Acacia species (see below) planted in typical summer lawns grow well because the greater availability of water comes at a time of vigorous growth of the trees. The added water in combination with seasonal applications of fertilizers (primarily applied to the turf) can stimulate rapid tree growth. Initially this growth may be desirable. In the long term frequent, shallow irrigation of the turf encourages surface rooting and makes the trees more subject to wind throw (up rooting caused by high winds). Supplemental deep irrigation, specifically for the tree, in the area from the trunk to just beyond the canopy drip line, will promote the development of a broader, deeper root system. Both deep and frequent shallow watering, during the growing season, will also encourage the development of a dense leaf and branch canopy. When trees are actively growing, no more than 20% of the branches or foliage should be removed monthly, during the trees early development (3 to 5 years post installation). The intense shade produced by trees like Chilean Mesquites can inhibit the growth of most common and hybrid Bermuda grasses. Shaded grasses are thinner, less vigorous and easily damaged by foot traffic, more subject to disease and invasion by weed or undesirable grass species. Mesquites are not unique in this regard but show this adverse interaction in far fewer years than do Native Mesquites, Blue Palo Verde, Sweet Acacia and other broad, dense canopied desert trees.

Year Round Lawns: Winter lawns create special problems for many desert trees because large amounts of water and fertilizers are applied during seasons (fall and winter) when desert trees should be going dormant. Semi-deciduous trees, for example, will continue to produce new tender growth if water is available and temperatures are warm. Such actively growing trees can be severely damaged or even killed when freezes occur. Reducing or eliminating irrigations in fall and winter is an effective way of encouraging dormancy in semi-deciduous desert trees. The installation and maintenance of winter lawns eliminate the opportunity to promote dormancy and hardening off in some desert species.

Lawn Maintenance Issues: Lawn maintenance activities around trees like mowers and line trimmers can damage almost any tree specie planted in turf. Trees that develop little if any bark and have soft trunks, like Blue and Sonoran Palo Verdes, are particularly prone to serious injury. Proper tree placement, grass-free tree wells and physical barriers or guards around the base of trees can reduce the likelihood of damage.

Creative designs can remedy some of these situations. Where possible segregate trees into hardscape areas or areas with rock mulches instead of within turf areas. This is done very successfully and to the benefit of both trees and turf in many award winning landscapes and world renowned desert golf course designs. Avoid using particularly vulnerable species, especially in areas that are regularly over-seeded with winter grasses or where they would be especially vulnerable to injury from mowers and trimmers. Provide regular, deep, well-distributed irrigation of trees to promote deep and dispersed root systems. Carefully consider the list below when incorporating desert adapted trees into your landscape designs.

Trees that generally tolerate lawn planting include:

Mesquites (all species); Screw Bean, Thornless 'AZT', Native, Honey

Sweet Acacia (Acacia smallii)

Desert Willow (Chilopsis linearis) 'AZT'

Shoestring Acacia (Acacia stenophylla)

Cat Claw Acacia (Acacia greggii)

Trees that generally do not tolerate planting in lawns:

Blue Palo Verde (Cercidium floridum)

Sonoran Palo Verde (C. praecox)

Foothill Palo Verde (C. microphyllum)

Mulga (A. aneura)

Ironwood (Olneya tesota)

Texas Ebony (Pithecellobium flexicaule)

This is not to suggest that it is impossible to maintain any of the trees listed above successfully in lawns, but rather that these trees will require special care and management to survive in these settings. In Summary, several factors must be considered when planting desert trees in turf areas: 1) is the year round maintenance and irrigation of the turf compatible with the specie of trees; 2) will the growth of the trees adversely affect the turf; and 3) does the additional maintenance, care and potential risks of tree death justify the use of this specie in a turf area.