Care and Maintenance of Small Stature, Desert Trees
Small statured desert-adapted trees are an essential part of the landscape tree palette. In patio plantings, as accent plantings to compliment larger or deciduous trees, in narrow spaces between structures or adjacent to pedestrian areas, small stature trees can provide shade, texture, color and screening in difficult locations. Their wide adaptability, durability, and wide array of shapes, textures, leaf and flower colors, and low maintenance make them ideal for many landscape applications.
Acacia craspedocarpa, Leather Leaf Acacia,
Small stature, and a fair number of medium and large stature, desert tree species are essentially large to very large shrubs with a multiple trunked, natural forms. In native desert settings, without any pruning, all these trees will form a hemispherical canopy with branches extending to the ground. This is easily seen in unpruned landscape specimens of Acacia craspedocarpa, Leather Leaf Acacia, Acacia constricta, White Thorn Acacia, Dodonaea angustifolia, Hopbush, Cordia boissieri, Texas Olive, Acacia greggii, Catclaw Acacia, Sephoria secundaflora (Green and Silver Peso), Texas Mountain Laurel, and others.
Sophora secundiflora, Texas Mountain Laurel
These growth habits provide several valuable adaptations to hot, dry desert conditions. The canopy shape and dense branching force drying deserts winds over and around the leaf canopy, rather than through the canopy, and helping reduce evapo-transpiration. Branches extending to the ground and the dense leaf canopy generate ample shade beneath the canopy, reducing the evaporation of moisture from the soil surface.
Misguided attempts to prune multiple trunk desert species, of all statures, is a common yet foolish errand that requires considerable investment of time and effort that only produces trees that are physically, physiologically, horticulturally, and aesthetically compromised. A more detailed discussion of proper pruning practices can be found at www.aridzonetrees.com. The adverse effects of converting multiple trunked, small stature trees to single trunked specimens are far worse than for larger stature trees.
Cordia boissieri, Texas Olive
Photosynthetic capacity is directly related to tree growth as it is defined as a measure of the rate at which photosynthesis occurs. Plant leaves convert CO2 and light from the sun to produce glucose. Glucose serves as an energy source and a building block for more complex metabolic and structural molecules in the plants. External processes and environmental conditions that reduce photosynthetic capacity directly reduce/slow growth.
Dodonaea angustifolia, Hopbush
Improper pruning practices, especially those associated with converting multiple trunk trees to single trunk, significantly reduce the size and density of the leaf canopy and photosynthetic capacity, in both the short and long term. In the short term, there are fewer leaf bearing branches and net fewer leaves to support photosynthesis. As a result, photosynthesis, and growth slows. In the long term, the time required to return to a “normal” level of photosynthesis and growth will be dictated by the original size of the canopy, the amount removed, and species inherent capacity to regrow its canopy. The larger percentage of the canopy that is removed to accomplish the objective of the pruning, the longer and slower the return to normal growth.
Acacia aneura, Mulga
Almost all small statured trees fall within the group considered slower growing. All pruning sets back growth. Larger trees, depending on the season of the year, may return to near normal canopies in 4 to 6 months (hence regular, light seasonal pruning is recommended for these species). Smaller statures may take years to overcome the effects of severe, improper pruning. Given that the role of these trees is, most often, to add leaf and flower color, texture, and variety to the landscape, severe pruning could eliminate these benefits for years.
As with all trees, the landscape design should place them in locations that will complement their nature shape and form without requiring excessive pruning. Proper placement will necessitate an appreciation for the mature dimensions of the tree, its interactions with adjacent biological and non-biological elements of the landscape, and its compatibility with the anticipated uses for the landscape (pedestrians, shade, screening, etc.). In the right environment, small stature, desert-adapted trees bring beauty and variety to any landscape.
Partial List of Small Stature Trees
Grown by AZT
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Acacia aneura, Mulga
Acacia constricta, White Thorn Acacia
Acacia craspedocarpa, Leather Leaf Acacia
Acacia greggii, Catclaw Acacia
Cordia boissieri, Texas Olive
Dodonaea angustifolia, Hopbush
Sophora secundiflora (Green and Silver Leaf),
Texas Mountain Laurel