GV?Gardeners: Identify and eradicate invasive grasses

Currently thriving along our roadsides, common areas, and arroyos are two very invasive grasses.

These non-natives are buffelgrass and fountain grass, which to the untrained eye are difficult to tell apart.

Both grasses spread by seed or root runners.

Fountain grass (Pennisetum setaceum) is a robust clumping grass still being used as a common landscape ornamental.

It is increasingly spreading into natural habitats, especially in washes, where it displaces native grasses and other vegetation.

Although it doesn’t usually spread as rapidly as buffelgrass, it does encourage habitat-disrupting fires and loss of native vegetation.

Usually growing to 1-1/2 to 4 feet tall, fountain grass forms a dense clump with erect stems and slender leaves. It blooms in summer and fall, depending on rain.

The long feathery flower heads resemble bottlebrushes and are 6 to 15 inches long. Seeds, which are off-white, pink, or purple, may survive six years in the soil before germinating.

Buffelgrass (Pennisetum ciliare) was introduced in Arizona as a forage crop in the 1930s.

It is described as a fire-loving, drought-tolerant perennial that spreads in wet or dry years.

It forms dense infestations that crowd out native plants.

Active or dormant plants can burn year round, producing very hot fires.

Such a fire will kill most native plants in its path, because the Sonoran desert is not adapted to fire.

This shrubby bunch grass produces new leaves and flower spikes very quickly after light rains anytime of the year.

Growing to 1-1/2 feet tall and up to 3 feet wide, older plants branch densely, very open, and nearly without form, giving it a “messy” appearance.

Tiny whitish hairs can be seen at the leaf base where it meets the stem.

This plant can quickly green up after rains, and just as quickly turn to a straw color when dry.

Buffelgrass flowers look like a bottlebrush, tan when mature and reddish to purplish when young.

Field evidence in Arizona suggests that seeds may survive for 3 years.

Unlike fountain grass, when the seeds fall from this plant, the central stem (rachis) where the seeds were attached, is extremely rough to the touch.

To distinguish these grasses apart, keep in mind that fountain grass is taller, leaves are narrower and stand more erect, giving it a symmetrical shape.

Fountain grass flowers can be from 6 to 15 inches long. Buffelgrass, with shorter flowers, will appear to lack a defined form, since the 1-1/2 inch wide leaf blades tend to fall away from the plant center, giving it an “unkempt” appearance.

There are two ways to work at eradicating these grasses.

Most success has come from removing the plant and root ball by the use of a digging bar.

After dug out, plants are placed into a large trash bag and disposed of in the landfill. Pulling out can be done any time of the year.

Herbicide control is an effective way to kill invasive grasses, but must be done when at least 50 percent of the grass’ leaves are green.

Glyphosate herbicides such as Roundup Pro or Kleenup Pro in a 2 percent solution are non-selective, post-emergent herbicides, and can also kill non-target grasses and plants. There is no effect on seeds.

Each individual plant must be carefully sprayed to coat the leaves.

Re-treatment is commonly necessary.

This method has been effective at the University of Arizona Desert Lab on Tumamoc Hill in southwestern Tucson.

There are currently a number of “weedwacker” teams across Pima County who labor diligently year-round to control these invaders.

The Tucson Mountains group proudly state that because of its efforts, no buffelgrass can be found roadside from Gates Pass to the Desert Museum entrance.

This is extremely hard work in often remote, rugged areas, but these devoted folks have a mission.

The control of fountain grass and buffelgrass will take constant vigilance. Areas once cleared may be re-infested.

Required is a minimum of three years of sustained effort to eliminate the vast quantities of viable seeds that remain in the soil.

What can you do? Start in your neighborhood by setting a good example and removing invasive grasses from your own yard.

Then encourage your neighbors and friends to do the same.

Very important is to ask your Homeowner Association to monitor and clear common areas of these invaders.

Practice identifying invasive grasses… not all are bad… there are many beneficial grasses that belong in the Sonoran Desert.

Mary Kidnocker is a Master Gardener who writes frequently about the subject from a local perspective. Her columns are featured each Sunday. She is currently president of The Green Valley Gardeners.