Vegetative propagation techniques (cloning) for desert adapted trees many offer new ways to increase the variety and selection of nursery grown trees. Growers are always searching for trees that have attractive qualities like flowers color, bloom season, shape and growth rate. Because cross pollinating is common among desert species, seedlings rarely exhibit all the characteristics found in the "mother" tree. By using vegetative parts of a selected mother tree for propagation , growers can produce similar trees.

Two popular desert adapted tree species where clonal propagation will prove valuable are Thornless mesquites (Prosopis chilensis) and Ironwood (Olneya tesota). Thornless mesquites are being used increasingly in a variety of commercial and residential urban landscape settings. Mesquites are rapidly replacing elms and ash trees in applications like streetscapes, parking lots, open spaces, parks and building entries. Many locations require a strong, upright growth habit that accommodates pedestrian traffic.

Growers have responded by producing more standard trunked mesquites but this form appears to make mesquites more prone to wind throw. An alternative that combines wind stability and is pedestrian friendly are V-shaped, upright, low breaking and multiple trunked selections. To grow such trees from seed would require a high level of rouging (throwing away seedlings with undesired forms). By collecting propagation wood from mature trees that exhibit this form, growers are better able to effectively meet the expanding market for these forms.

Ironwood present a different set of horticultural challenges. Emphasis is being placed on identifying selections that demonstrate faster growth rates, upright, V-shaped growth, more open branching patterns and larger, more numerous and darker colored flowers. Cloning this specie has proven difficult and it is likely that a combination of both vegetative and seed selection methods will be used to improve commercially produced Ironwoods. Even modest improvements in growth rates or tree uniformity will significantly enhance the popularity and use of this unique Sonoran desert native.

Observing Ironwoods in the desert it is easy to see there are a variety of flowering patterns. Some are deep purple while others are pale lavender to creamy white. At present most landscape architect are not using Ironwoods as a color accent tree. The development of selections that exhibit more striking flower displays will further encourage the use of this tree for its beautiful and unusual flowers.

Before bringing new trees into the landscape market, growers must do extensive nursery evaluation. This process involves several years of observation so that growers understand the nature, growth, temperature sensitivity and other key growth perimeters. While new selections may exhibit characteristics that we value They may also carry deficiencies like weak rooting, insect and disease problems or any unobserved horticultural short comings. Nursery evaluations also provide an opportunity to assess the maintenance requirements of new selections. Clonal propagation coupled with the careful evaluation of new selections will ultimately offer landscape architects a wide array of arid species that are well adapted to ever expanding uses of desert adapted trees.