   Thorny Native Shrubs of the Verde Valley - March 15, 2006 Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Plants have a range of unique adaptations to help them survive in arid environments. Some desert plants are ephemeral: taking advantage of moisture when it comes and completing their life cycle over the span of weeks if need be. Cacti have succulent stems and their leaves have become spines. Cactus spines not only protect them from herbivory, but can also shade the plant from the intense sun. Other arid plant adaptations include: pubescent (hairy), waxy, small, and/or folded leaves; extensive or deep root systems, and dormancy during drought periods. During dry periods, woody plants are sometimes the only forage available to grazing/browsing animals in arid environments. Some woody plants, such as creosote bush, have chemical compounds that inhibit or prevent herbivory. Others have prickly leaves or thorny stems that make them less palatable to browsers. Their thorniness also keeps them from being trampled by animals including humans. Below, I have listed several thorny native shrubs (and small trees) found in the Verde Valley area. If you have them on your property, don’t be in a hurry to rip them out. They are well adapted to our climate and soils. Some of them are also being grown by for sale in nurseries. Catclaw acacia (Acacia greggii) is widespread in the southwest at elevations below 4,500 ft. It is often a shrub but become a small tree with age. Bipinnate compound leaves are gray green and deciduous. Pale yellow, fragrant flower spikes bloom in spring and mature into flattened, twisted bean pods. Short, curved spines occur singly along twigs. These can rip clothing and skin. Cultivated by nursery industry. Crucifixion thorn (Canotia holocantha) grows in Arizona, southern Utah, southeastern California, and northwestern Mexico between the elevations of 2,000 and 4,500 ft. Leaves small and deciduous. Branches are green and tipped with spines which appear sharp but are relatively soft. White inconspicuous flowers. Rarely taller than 15 ft. Very unique plant that grows in almost pure stands in areas of the Verde Valley. May never be grown for sale commercially due to limited range and odd appearance. Algerita (Mahonia fremontii) grows in Arizona, Utah, Colorado, California, and New Mexico between the elevations of 4,000 and 7,000 ft. A dense erect shrub with very spiny, evergreen, gray-green, compound pinnate leaves. Has yellow flowers in spring which ripen into bluish-black berries. This plant has tremendous potential for use in low water use landscapes. Some growers appear to propagate it, but availability may be limited. Wait-a-minute (Mimosa biuncifera) is widespread in the southwest at elevations between 3,000 and 6,000 ft. Bipinnate compound leaves are deciduous and dark green (smaller than those of catclaw). Cream colored flower clusters bloom in spring and mature into flattened bean pods. Short, curved spines occur in pairs along twigs. Paired spine arrangement also makes it easy to discriminate from catclaw acacia. This plant is not available in nurseries, but has some potential for use in landscapes. Velvet mesquite (Prosopis velutina) is widespread in the southwest at elevations below 5,000 ft. Shrubby when young but becomes a medium sized tree with age. Bipinnate compound leaves are gray green and deciduous. Pale yellow-green flower spikes bloom in spring and mature into flattened bean pods. Roots can grow deep to extract water. Prized as firewood and cultivated by nursery industry. Graythorn (Ziziphus obtusifolia var. canescens) grows in Arizona, Utah, Nevada, California, and Mexico between the elevations of 1,000 and 5,000 ft. A dense erect shrub with small, deciduous leaves. Grayish twigs are tipped with sharp spines. Small flowers are followed by blue-black berries which are excellent feed for quail and doves. This plant is not available in nurseries, but has some potential for use in landscapes. To see photos of these plants, you may visit Doug Von Gausig’s Plants of the Verde Valley and Sedona web site at: www.naturesongs.com/vvplants/. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |