In landscape settings, created in the course of construction and land development, a third type of environment is found. In these situations, neither water nor space are limiting factors, so that desert trees can grow rapidly in both directions. This growth can cause problems in areas where people and vehicles need to pass, such as along sidewalks and paths or in parking lots. Pruning is used to control and direct the growth of woody plants, particularly trees. Unfortunately, in many instances, tree structure and balance are destroyed in the process. Many multi-trunked mesquites, for example, have been pruned to a single crooked trunk in the mistaken belief that the tree width can be reduced. Most multi-trunked trees take up no more horizontal space than do single-trunked trees. The several (3, 5, or 7, in most cases) trunks can be selectively pruned to establish the lowest main laterals or scaffold branches at the height desired. Once the tree is "lifted" it can then be "laced out" or thinned. This technique allows the wind to more easily pass through the branches since the tree no longer has its lower branches to divert the wind around and over.

Growers of desert tree species typically produce both single (a) and true multiple trunk trees (trees which product multiple vertical branches at or near soil level) as well as "low-breakers" (trees which branch from 6 to 24"). A higher percentage of singles are produced by most growers than exist in nature. This tendency can be attributed to the following: 1) Convenience--it is often easiest for a nursery worker to select the largest stem and tightly stake it up, thus avoiding having to make critical pruning decisions required to produce attractive multi-trunk trees; 2) Convention--a client's preconceived notion of what a tree "should" look like often incorporates the straight-trunk, round- headed "lollipop" effect; and 3) Confusion--the incorrect assumption that a single trunk tree takes up significantly less space than a multi and that multi-trunk trees interfere with pedestrian and vehicle traffic. As a result, singles are often specified for use in parking lots, street plantings and pedestrian paths, when multis are equally appropriate.

There are situations in the landscape where even narrow multiple trunked trees would not be appropriate (e.g. a planting strip between a sidewalk and a wall). In such an instance it would make sense to select desert tree species with a vertical rather than a spreading habit. Choices include Palo Blanco (Acacia willardiana), Shoestring Acacia (A. stenophylla), and Mulga (A. aneura). Such trees would function better than species with crowns that would be crowded by the wall.

In summary, the use of multi-trunked desert trees in the landscape should be encouraged in all facets of the landscape industry, from design to construction to retail sales. The natural grace and beauty multi-trunk trees bring to the urban landscape are important factors in health, aesthetics and durability of desert landscapes.

(a) The definition found in Hortis Third (Macmillian Publishing Company, New York) more accurately describes small statute, patio-type trees (with 3 to 6' of clear straight trunk) like trees roses, tree fushsias and azlaeas than it does the vast majority of desert adapted tree species. We have elected to use single trunk to better create a distinction between single trunked, and multiple trunked specimens.