By Kathleen Ferris
Desert shrubs do not thrive when homeowners and landscapers shear them into geometric shapes, such as balls, squares or inverted pyramids. Regular shearing weakens these shrubs, detracts from their beauty, discourages them from flowering, and shortens their lives. Desert shrubs just don’t conform to formal garden expectations. It’s painful to see these rugged plants neatly shaped in Valley parking lots, front yards and streetscapes.
Shrubs that grow in humidity and get regular rain survive and recover more easily from regular shearing to create hedges and formal shapes. Desert shrubs are different. These shrubs survive all year long on sparse resources under relentless sun and arid conditions. They can’t withstand the added stress of shearing.
Leaves make and store food that shrubs need to grow and to fight off disease. When gardeners regularly shear off leaves, the shrubs use their stored energy just to survive. They live in perpetual stress.
Sheared desert shrubs build shells of small leaves and the insides get dense with woody branches. Eventually, shrubs can’t make enough leaves and woody holes begin to break through the shell. The shrubs get ugly and eventually wear out.
Most shrubs familiar to Valley homeowners, such as Texas sage, California rosewood, and creosote, look their best when they are left alone. They will remain happy with a few inches of careful trimming that includes removing their dead and diseased limbs.
If you must prune, take out a maximum of 1/3 of the shrub’s older, larger branches. Cut the branches at the point where they attach to the plant or at the ground, not where the sidewalk ends. Remove branches that are rubbing against each other. The goal is to allow light and air to reach deep inside the shrub. That way a shrub will grow leaves along every branch instead of a shell of leaves only at the tips.
Desert shrubs need to be wider at the base. Bottom branches shade shrubs’ roots, maintaining moisture and cooling the soil. When gardeners remove the ground level branches, they expose the soil to harsh sun and drying.
Nurseries have desert shrubs that will grow to any height that fits a garden’s design. Buying the right size shrubs help avoid over pruning to make plants fit the space. For example, a gardener can find oleanders that grow to a height of 3 feet or 20 feet. Getting the right size also means less maintenance.
If nothing else will due but a formal hedge, there are a few shrubs that can handle the shearing, such as the desert-adapted jojoba or the Japanese boxwood or myrtle, which require more water. Even these shrubs need to be sheared to a shape that is wide at the bottom or they will lose their leaves on the lower branches.
An ideal desert-garden hedge uses a variety of lightly pruned shrubs in a staggered line, similar to the plants scattered along a desert wash. Leave the formal hedges for English gardens and bring a little desert design to your yard.
Find out how to prune and when to prune shrubs of all kinds at the University of Arizona Cooperative Extension, get pruning tips and resources at LandscapingWithStyle.com, or find a free class close to you.
For 45 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit www.amwua.org.