Trees Introduction


There are trees for shade and shelter, trees that provide fruits and nuts, ornamental trees and flowering trees, deciduous and evergreen.  They come in all shapes and sizes from tiny dwarfs to the towering Redwoods, windswept Bristlecones to whimsical topiary.  Trees exist in all but the very driest or coldest regions of the world.

Water Use

Some trees suitable for arid environments are[1]:

  • Desert willow (Chilopsis linearis)

  • Russian Olive (Elaegnus angustifolia)

  • Scrub oak (Quercus gamelii)

  • Idaho locust (Robinia idahoensis)

  • One-seed juniper (Juniperus monosperma)

  • Colorado pine (Pinus edulis)

  • Singleleaf pinyon (P. monophylla)

  • Ponderosa pine (P. ponderosa)

For the purposes of determining the water requirements for landscapes, trees can have a significant impact. The presence of trees can greatly increase density of plants in a landscape. The effect on evapotranspiration from the amount of plant material in a landscape is evaluated by the density factor. This density factor can be increased from 100% (for a full ground covering) to 130% by the addition of tree canopy[2].


Trees provide countless benefits from reducing erosion and pollution run-off to cooling and CO2 absorption[3].  Many municipalities understand the many benefits that trees provide for their communities and have ordinances in place that specify the number, size, and type of trees used in any new development.  Additional benefits can found at TreeLink [4], a nonprofit organization devoted to raising awareness and support for healthy urban forests and serves as an information repository and networking center for urban forestry professionals while providing outreach to land agencies, academics, green industry and the general public.

[1] Ellefson, Connie, Tom Stephens and Doug Welsh. (1992) Xeriscape Gardening: Water Conservation for the American Landscape. Macmillan Publishing Co., New York.

[2] University of California Cooperative Extension and the California Department of Water Resources (2000) “A Guide to Estimating Irrigation Water Needs of Landscape Plantings in California.” Accessed August 22, 2011

[3] Arbor Day Foundation. “The Value of Trees to a Community.” Accessed August 5, 2008.

[4] From a water efficiency perspective trees play an important role is shading other plants and reduc TreeLink Log On  “Branch Out. Benefits of Trees.” Accessed August 5, 2008. the water requirement for those plants that benefit from the shade.