GV?Gardeners: Invasive grasses threaten neighborhoods

A number of local citizens have been expressing their anxiety over the amount of exotic grasses showing up along roadsides, property boundaries, and in neighborhood common areas around our community.

With many annual homeowner association meetings scheduled this time of year, perhaps it is again time to talk about invasive weeds, especially grasses.

Perhaps at these meetings, a discussion of how to identify these invaders and then how to begin eradicating them is in order. Groups may be formed to start working on this problem and establishing a new weed management program in their own neighborhood.

Among our toughest challenges are green fountain grass (Pennisetum setaceum) and buffelgrass (Pennisetum ciliare). Probably one of the biggest obstacles for eradication is that these are lovely, decorative grasses. It can be difficult (and unpopular) to tear out something so attractive in the landscape.

Green fountain grass spreads aggressively by seed and forms dense clumps, choking out native plants and altering wildlife habitat. It is also an extreme fire hazard to homes, native plants and animals. This robust perennial clumping grass is a common ornamental in landscapes, while spreading aggressively. Especially happy in washes and neighborhood common areas, it displaces native grasses and other vegetation.

Buffelgrass is a close relative to fountain grass, and is also a very dangerous fire threat. Still sold as cattle forage in some places, buffelgrass is an aggressive invader that has spread along roadsides into urban areas and wild lands. Resulting extremely hot fires can kill saguaros, palo verdes, and other “signature” plants of the Sonoran desert, but fire does not even slow up buffelgrass!

What can be done to prevent these grasses and the disastrous results of their invasion? The first thing is to recognize the threat that if left uncontrolled, these invaders will irrevocably alter the Sonoran Desert. Do some research and learn to identify the “bad guys.” Understand that it is important to the environment right here in our own neighborhoods.

Homeowners can set a good example by removing invasive grasses from their yards, and encouraging friends and neighbors to do the same. There are two ways to eradicate these grasses effectively. Herbicides (Glyphosate/Roundup) can do a good job at killing actively growing, green grasses. Follow label instructions carefully.

Manual removal is very effective if the root mass is entirely removed. Disking is not advised as it will expand the infestation by spreading root nodules. Mowing is not effective, but it can be coupled with herbicide treatment. Regardless, to prevent re-infestation, vigilant monitoring and spot eradication may be required indefinitely.

You may ask your HOA to get involved in your neighborhood. Walk through common areas occasionally to peruse what changes in vegetation have occurred. Report the invaders to your landscape chairman, and ask that action be taken.

Descriptive pamphlets on invasive weeds are free for distribution at neighborhood meetings. Trained volunteers are available to work with community groups on the identification, mapping, and removal of invasive grasses. Speakers for public meetings can be arranged. A good starting place may be the Arizona Native Plant Society, Tucson Chapter. Its Web site is: www.aznps.org.

A pamphlet, “Wipe Out Weeds,” is available from Pima County Regional Flood Control District, (520) 243-1800. Another is “Wanted Buffelgrass Dead and Gone” put together by several interested organizations and available by calling (520) 877-6000 or clicking on www.buffelgrass.org.

Time is of the essence. For example, buffel grass spreads exponentially — meaning it will double in numbers every year. We may never totally eradicate these invasive grasses, but we can work at managing to control their spread. It is important! These plants threaten the very unique plant and animal diversity of Southeastern Arizona.

Mary Kidnocker is a Master Gardener who writes frequently about the subject from a local perspective. Her columns appear Sundays. She is president of The Green Valley Gardeners.