   Pampas Grass: Riparian Invader - October 20, 2004 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County The Verde River riparian corridor is being colonized by several non-native, invasive plants. Among these are salt cedar (Tamarix ramosissima), water primrose (Ludwigia hexapetala), tree of heaven (Ailanthus altissima), Eurasian water-milfoil (Myriophyllum spicatum), and Pampas grass (Cortaderia selloana). While resource impacts of salt cedar have been widely publicized, the other species listed above are not as well known. Pampas grass is till sold in nurseries and is already increasing along the Verde. Let’s take a closer look at Pampas grass, potential resource impacts, and discuss some alternative plant species. Pampas grass is native to Brazil, Argentina, and Chile. It is a large bunchgrass that can grow to six feet tall in Arizona (taller when flowering). The edges of the leaves are saw-edged and can inflict a nasty cut if you get too close. The plume-like flower stalk differs slightly between male and female plants. These plumes are creamy white to pinkish and valued for dried flower arrangements. Pampas grass spreads by seed which can be transported long distances by wind and water. It prefers full sun and does require some moisture to become established. It has no natural enemies and is not grazed by livestock or wildlife. The problem with Pampas grass and other invasive plants is that they successfully outcompete native plants for light, soil moisture, and nutrients. As they increase in numbers, desirable native plant populations are reduced as are other plant, animal, and insect species that depend on the displaced native plants for survival. Pampas grass has caused serious resource impacts in Hawaii, California, New Zealand, and South Africa. Rather than planting Pampas grass, select a native ornamental grass species instead. Below is a list of natives that are noninvasive, drought adapted, and excellent alternatives to the dreaded Pampas grass. One of the showiest grasses is Muhlenbergia capillaris var. Regal Mist. This grass forms a clump 2-3 feet tall and forms deep pink seed heads in the fall. The seed heads are one foot higher than the grass and are very striking. It thrives in full sun, but tolerates partial shade. It does require some irrigation to look its best during summer. It is hardy to 0 degrees F. Deer grass (Muhlenbergia rigens) is can be found in our local mountains, handles any soil, and thrives in either full sun or partial shade. It has gray green foliage, reaches 4-5 feet in height, and blooms in slender spikes during fall. It is hardy to 0 degrees F. Alkali sacaton (Sporobolus airoides) has been used extensively for reclamation projects, but has excellent potential as an ornamental. It gets 3 feet tall and 4 feet wide, has wide leaves, and produces a rosy flower spike. It tolerates salty soils and is native to the Verde Valley. It is hardy to -20 degrees F. Mexican feather grass (Stipa tenuissima) is a close relative of our local needle and thread grass (Stipa comata). This grass is 18-24 inches tall and has very delicate and weeping foliage. It is hardy to -10 degrees F. Globally and nationally, invasive species take a great toll on native ecosystems and cause serious economic impacts. We are still at the early stages of the Pampas grass invasion along the riparian corridors in the Verde Valley. You can take steps locally to protect the Verde River and the other creeks in the Verde Valley by learning more about invasive plants and using native and non-invasive plant species in your landscape. The University of Arizona Cooperative Extension has publications and information on plant selection and noxious weeds. If you have 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/. |