Written by Jeff


All photographs courtesy of the City of Scottsdale, AZ (see link below)

When you think about the desert, you usually don’t get mental images of areas overrun by weeds and invasive plants. After all, a desert receives a dozen inches or less of rain a year on average. I was very surprised to learn that invasive plants (read weeds) pose a potential serious problem for the Sonoran Desert. What I am reporting below was gleaned from a presentation given to the Maricopa County Master Gardeners as part of the February, 2009 Monthly Update.

Jerry Miller is a retired physics professor who became interested in preserving the McDowell Mountain Preserve and saving it from invasive plants. Through perseverance, pluck and persuasion, the program has had some successes thus far. The program he presented is called:

SCOTTSDALE’S INVASIVE WEED MANAGEMENT PROGRAM: FOUR YEARS OF SUCCESSES AND FRUSTRATIONS

There are a total of eight invasive plants which have garnered the focus of the group:

1. Desert Broom (Baccharis sarothroides) – native
Desert Broom

2. Red Bromegrass (Bromus rubens)
Red Bromegrass

3. Buffel Grass (Pennisetum ciliare)
Buffel Grass

4. Tamarisk/Salt Cedar (Tamarix spp.)
Tamarisk/Salt Cedar

5. Fountain Grass (Pennisetum setaceum)
Fountain Grass

6. Malta (Maltese) Starthistle (Centaurea melitensis)
Malta (Maltese) Starthistle

7. Saharan Mustard (Brassica tournefortii)

Saharan Mustard

8. Bermuda Grass (Cynodon dactylon)
Bermuda Grass

All of these are non-native except Desert Broom. It is important to note the Latin names as other species or cultivars may not be invasive and may suitable for use in and around the geographic areas under discussion. The Fountain Grass mentioned above (Pennisetum setaceum ) is extremely invasive and, unfortunately, still in use by many. The purple Fountain Grass (Pennisetum setaceum ‘Rubrum’) is not invasive and has a good number of ornamental uses even though in some parts of the country it does grow fast and has a tendency to “take over.” Having said that, when in doubt, find another plant.

Interestingly enough, the desert has a microbiotic crust (desert pavement) that prevents many weeds from taking hold. This serves the desert well, but when man intrudes by walking, digging or building, the crust is destroyed and a foothold may be created for certain plants considered weeds.

The McDowell Mountain Preserve is made up of 36,400 acres of city and state-owned property according to Mr. Miller. Unfortunately, the state of Arizona offers very little help in maintaining this area. The Invasive Weed Program (IWP) began in 2004 when certain weeds were verified and mapped. Buffel grass, for example, has been distributed through the area by human traffic – hikers and campers. To be most effective, many constituencies must remain involved in solving the weed problem. The city of Scottsdale, the McDowell Sonoran Preserve, the McDowell Sonoran Conservancy and volunteers all join forces to work on ridding the area of numerous stands of these invasive plants.

The management plan has eight distinct goals:

  • Produce a city-wide noxious weed list primarily for education at this time
  • Maintain the strict use of herbicides in the preserve and surrounding areas
  • Develop sophisticated monitoring and mapping systems
  • Develop a network of volunteers to complement the work of city staff
  • Develop an expendables budget with the city
  • Develop cooperative agreements with neighbors of the preserve
  • Develop new codes requiring contractors to be responsible for invasive plant eradication and mitigation on disturbed soils
  • Develop a relationship with other groups fighting invasive weeds to learn about new problems and effective strategies

If you live in and around the Sonoran desert and you care to help preserve native species and habitat that contribute to the beauty of this remarkable environment, contact your local government to learn how you can work toward reducing the loss of native flora. References are listed below to guide in the use of appropriate planting material and providing resources for reducing species that encroach on our the Sonoran Desert habitat.

Gardening on the Moon, www.gardeningonthemoon.com, originally published this post


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Article References:

City of Scottsdale – Invasive Plants in and Near the McDowell Sonoran Preserve

McDowell Sonoran Preserve – General

McDowell Sonoran Preserve -Preserving the Ecosystem

McDowell Sonoran Preserve -Invasive Weed Program

McDowell Sonoran Conservancy- General