Gardening hangovers, Part 3: fountain grass

Grasses are among California’s most prolific weeds. Exotic bromes and other annual grasses now carpet millions of acres, displacing of native wildflowers, bunch grasses and shrubs.

Most arrived with 19th century settlers and livestock (as contaminants in feed or lodged in animals’ coats, for example). But in recent years, ornamental grasses have joined the fray.

“Grasses are useful in a landscape,” says Jim Folsom, director of botanical gardens at the Huntington, “but by nature they are invasive; being a grass generally means being able to cover a lot territory fast.”

A nasty example festers at Arcadia Wilderness Park. Three acres of a steep, dry slope are bristling with a billowy plant with fuzzy seed heads, called fountain grass (Pennisetum setaceum). This runaway garden plant is also slurping up water in a nearby stream bed. Drew Ready of the nonprofit Los Angeles and San Gabriel Rivers Watershed Council says it’s converted “a biologically diverse stand of chaparral” into “a biological wasteland.”

The grass’ bad seed gets around easily — roving perhaps miles in strong wind. It has most likely already plopped into the adjacent Angeles National Forest, and needs only a disturbance -- fire or mudslide — to spread rapidly.

Like other alien grasses, fountain grass makes wildlands more fire-prone. “It provides a layer of really fine fuel that ignites very easily,” Ready explains. Coupled with an increase in human-sparked fires, exotic grasses threaten to extirpate plant communities on Southern California’s hillsides, including rare coastal sage scrub habitats. “Native species can’t endure these frequent fires and die off,” says Ileene Anderson, biologist with the Center for Biological Diversity.

In an attempt to keep fountain grass from escaping gardens, horticulturists have selected cultivars that aren’t supposed to reproduce, including purple-colored ‘Rubrum.’ But Ready doesn’t think they’re a safe bet: “Most nurserymen will tell you they’re not always sterile.” 

Ready advises gardeners to avoid all fountain grasses. “There are so many safe and beautiful alternatives,” he says, listing native deer grass, blue oat grass and "Canyon Prince" wild rye as examples.

He’s also concerned about the recent popularity of Mexican feathergrass; “because it spreads so readily by seed, it’s at best a garden nuisance; at worst it will become as much of a scourge as fountain grass.”

The Watershed Council promotes alternatives to the region’s most invasive plants on its Weed Watch website.

-- Ilsa Setziol

Coming Thursday: acacia

RELATED:

Gardening hangovers, Part 2: Mexican fan palms

Gardening hangovers, Part 1: periwinkle

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Photo credit: Ricardo DeAratanha / Los Angeles Times

Comments

[sheila]

So, if we are "victims" of, say, red brome, in our desert homes, can you please advise how to get rid of it? I try to hula hoe it but 90% of it grows out of the middle of another plant i don't want to kill, or out from under rocks. Hand-weeding several acres, stooped in the desert sun, is not really practical.

Any suggestions for getting RID of invasives would be appreciated by those of us who know not to plant them but are stuck with them...

thanks!

[Georgia]

Enjoying this series even though I live on the East Coast.

[Julia Posey]

Fountain grass pretty much blankets the sweeping hills from Monterey to Big Sur too. I was shocked when my family and I took that drive in September to camp in Big Sur. So much more growing than there was a decade ago.

[Ilsa Setziol]

Sheila,
I've e-mailed some experts in hope of getting you an answer on removing that brome.

[Emily Green]

I second all the appreciation for this excellent series. One of the key problems we have with invasives is that nurseries can still sell most of them with impunity. You even see the truly noxious nasturtiums in California "wildflower mixtures." The argument from nurseries is that they need to be allowed to propagate in nurseries here to sell the plants in less vulnerable areas, and also that judicious use of them should fall to the homeowner. This is nonsense. It is not beyond the wit of industry to adapt and sell less noxious plants. It could become a sales advantage for their brands to become emblems of Good Practice.

To stop invasives, we need the same kind of response from the USDA that it would have to plants infected with organisms that affect agriculture. You can bet that the official response to these plants would be a whole lot swifter if they were carrying Mediterranean fruit fly. The policy failure is that we have yet to put an economic value on protecting our wild spaces, and therefore have not directed the relevant agencies to act. So we are our own agencies. If you see invasives in your local store, ask for the manager. Write the chain. Selling these things has to become as unacceptable as, say, bringing foot and mouth into dairy country.

[Edith Allen]

Sheila,
Disturbing the soil with a hula hoe encourages more weed invasion. Hand pulling from small areas works, but not from large areas. Using a grass-specific herbicide (Fusilade) is effective before seed set. Grazing before seed set is also effective. The red brome seed bank declines after drought years, and control is best implemented when the seed bank density is low. This is a huge problem that land managers are trying to deal with, too.

[D Ready]

Annual grasses are difficult to remove completely from established landscapes. This is primarily due to an increased amount of available nitrogen, water, and well established seed banks.

Many use a pre-emergent herbicide, solarization and/or deep mulch applications. There are exceptions, but in the desert, gravel mulch is preferred to organic mulch. Unlike organic mulches, gravel won't break down and create the rich soils that many weedy annuals love. Desert winds also tend to blow organic mulches around and they need to be reapplied frequently where heat leads to quick decomposition.

These websites provide more detailed information:

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7441.html
http://cals.arizona.edu/yavapai/anr/hort/byg/archive/invasiveannualcoolseasongrasses.html
http://ag.arizona.edu/yavapai/anr/hort/byg/archive/springweedmgmt.html
http://www.mojavewma.org/redbrome.php

Good luck!

[Barbara E]

I agree with Edith Allen. Disturbing soil generally favors more weeds. Bromus rubens (red brome) is an annual weed that has low seed viability after one year. That's the good news. Seed in the soil that doesn't germinate probably won't the following year (2% germination rate after a year). Management includes killing grass before it goes to seed (either by hand or using an herbicide that is either grass selective or a pre-emergent- keeps seeds from forming new plants). Red brome does not like crowding or shade, so it is important to get native plants established in the area. Mulch seems to favor red brome improving germination rates - and of course some mulch has weed seed in it. So either get a goat or sheep to graze in early spring before the seed heads form, or mow it to the ground, or pull it out, or poison it. A good source is:
http://www.imapinvasives.org/GIST/ESA/esapages/documnts/bromrub.pdf

Good luck!

[D Ready]

Thanks for correcting and clarifying Barbara. Its always good when the pros chime in.

[sheila]

thanks for all the great pointers, ladies. i am at 4200 elevation so am just getting my wildflower bloom - i can't stand to kill the wildflowers (gravel mulch, grazing etc.) but this pesky grass seems to sense that and paces and sites itself accordingly.

there is the usual amount of healthy native vegetation, but most desert vegetation where i am (mesquite, cholla, creosote, etc) allows light through, especially in spring, so the grass grows freely anywhere it likes. i am very hesitant to use herbicides because i border a wilderness area, and have a lot of birds, jackrabbits, etc. but will investigate fusilade. there is (alas) no chance of selective grazing or hand-weeding multiple acres.

thanks again, i love this section of the paper!