Alliance to Combat Invasive Plants Grows

I have been working with Sustainable Conservation ( either directly, or through U.C. Davis Weed Science Program, for the past two years on developing, testing, and promoting a new weed risk assessment tool aimed at nurseries marketing horticultural plants, in an effort to reduce the sale and spread of invasive plants in California and the United States. Luckily, some of our efforts are paying off. I just received this notice from SusCon (yay!):

Alliance to Combat Invasive Plants Grows

San Francisco, CA (May 4, 2015) – PlantRight, a statewide campaign that partners with California plant growers and retailers to voluntarily phase out invasive plants in the state’s $11 billion horticultural industry, announced that it has secured key corporate commitments in promoting safe, non-invasive plants to benefit the state’s environment and people. Topping the list of industry partners are more than 200 The Home Depot stores in California. Once PlantRight determines a plant is invasive, The Home Depot will begin the process of phasing that plant out of its product mix.

“PlantRight’s collaboration with nursery retailers has been gaining slow yet steady momentum among garden centers large and small,” said Ashley Boren, Executive Director of Sustainable Conservation, which leads the PlantRight campaign. “Garnering the support of The Home Depot California represents a positive breakthrough for the industry in helping to curb the spread of invasive ornamental plants.”

Invasive plants reproduce quickly, blanket natural areas, and outcompete native plants and animals. Once they take hold, they are expensive to remove and control. Collectively, invasive species are the second greatest threat to biodiversity after human development. Invasive plants also threaten people by clogging waterways, increasing flooding risk and escalating fire danger.

“Partnering with PlantRight in California is the right thing to do for our communities,” says Brian Parker, Senior Merchant Live Goods with The Home Depot. “We’re committed to providing the best plant options for California, including drought tolerant and non-invasive varieties. Our growers are solid partners in these efforts, as we all are committed to protecting California’s landscape, wildlife and communities.”

Across California, for example, invasive broom plants have taken over entire landscapes of public and private land – including protected areas like state parks. Not all brooms are problematic, yet those that are cause significant damage. Some brooms alter soil composition in ways that are toxic to native flora, and each plant can produce up to 12,000 seeds – making it difficult to control once established. They form dense stands that can completely take over and eliminate native habitats.

These invasive brooms are so resilient that they often regrow after fire and grazing are used to eradicate them. Scotch broom was introduced to California as an ornamental garden plant in the 1850s, and was also widely used for roadside erosion control in the early 1900s. It was not recognized as a problem until the 1930s. Today, Scotch broom infestations cover more than 700,000 acres of open space, roughly the size of Yosemite National Park.

In Marin County near San Francisco, the municipal water district reports that French broom has taken over 1,400 acres within the watershed, and is spreading at a rate of about 50 acres per year despite tens of thousands of volunteer hours to remove it.

Giant reed (Arundo donax) has invaded streams and riverbeds throughout southwest California and in the Central Valley, damaging ecosystems and increasing fire danger and flood risk. At least 10 protected animal species in California, including the endangered bird the Least Bell’s vireo, suffer habitat loss due to invading giant reed. In wetter regions of the state, periwinkle (Vinca major) is blanketing forest floors, crowding out native plants and wildlife in the undergrowth, while playing host to such bacterial threats as Pierce’s disease, which threatens crops like wine grapes.

In California, the estimated cost to manage invasive plants tops $82 million each year. Nationally, the annual cost runs into the billions. That doesn’t include financial losses from reduced crop yields, land values and recreational activities.

“Half of all known invasive plants in California were introduced through horticultural channels – though not intentionally,” said Boren. “Considering that approximately 70% of plant sales are made at big-box stores, The Home Depot’s partnership with PlantRight will be transformative in making the industry a key problem-solver. This collaboration also shows that a healthy environment and a healthy bottom line can go hand in hand.”

Conservation groups, like the California Invasive Plant Council, agree that it’s more than just an environmental opportunity. “Preventing the spread of invasive plants, or the next Scotch broom invasion, saves untold millions in mitigation costs for our state and taxpayers, in addition to protecting California’s natural landscapes and native species,” says Doug Johnson, Executive Director of the California Invasive Plant Council, which complements PlantRight’s efforts by pursuing invasive-plant research and policy, leading restoration projects and educating the public about invasive issues.

“PlantRight makes it easy for the industry to do the right thing, voluntarily,” said Ashley Gill, Green Acres Nursery owner and Board Member at the California Association of Nurseries and Garden Centers, the state’s venerable nursery trade group.

“First and foremost, PlantRight really listened to the industry’s needs and concerns in developing an effective solution. They also knew blanket regulation, which can have unintended downsides for businesses and might still not end up fixing the problem, wasn’t the way. And, they used sound science to inform all decisions, which boosted the industry’s trust and desire to help.”

To assist its retail partners and other nursery professionals in making sense of what is, and is not, invasive, PlantRight maintains a list of high-priority garden plants that are invasive in California, and dozens of attractive, non-invasive alternatives. “We believe in coaching the do’s,” says Boren. “Our alternatives list is a practical way to help retailers and landscape professionals make the right plant choices.”

The plant list is a byproduct of PlantRight’s annual spring survey of California garden centers, which it conducts to stay apprised of trends with invasive garden plants throughout the state. Since conducting its first nursery survey in 2010, PlantRight has measured a 60% decrease in the number of retail nurseries selling invasive plants. PlantRight hopes to bring that number down much closer to zero in the near future.

“This partnership between The Home Depot and PlantRight will benefit gardeners of all levels, considering how challenging it can be to differentiate between deceptively beautiful, drought tolerant plants that are invasive, such as Mexican feathergrass, and those that are not,” said Missy Gable, Director of the University of California Master Gardener Program, whose volunteer members have played an instrumental role in PlantRight’s annual spring nursery survey.


PlantRight is a Sustainable Conservation-led campaign that works with leaders in California’s nursery industry to promote non-invasive plants exclusively for the state. The cornerstone of PlantRight’s educational, science-based content is its plant list, published since 2006, as a compass for the industry to successfully and voluntarily navigate invasive plant issues and opportunities. In 2006, virtually all retail nurseries in California sold one or more invasive plants. Today, less than 40% of California retail nurseries sell an invasive plant on PlantRight’s list. Visit to learn more.



Case Studies

INVASIVE:  Green fountain grass (Pennisetum setaceum)                                                            

Green fountain grass grows up to five feet tall in large clumps of long, narrow leaves with foxtail-like plumes in the summer. This invasive form of fountain grass has been observed invading deserts, grasslands and coastal areas. It has been reported as a major problem in 10 California state parks. It increases fuel load and therefore the frequency, intensity and spread of fire – and it quickly re-establishes in dense clumps after fires. Green fountain grass can become dominant in grasslands within two to three years if no control measures are employed. Fortunately for gardeners, the purple form of fountain grass is not invasive.

Non-Invasive ALTERNATIVES (just a few of many alternatives):

–          California fescue (Festuca californica)

–          Pine muhly (Muhlenbergia dubia)

–          Oriental fountain grass (Pennisetum orientale)

–          Purple fountain grass (Pennisetum setaceum ‘Rubrum’) note: this is a sterile cultivar

INVASIVE: Highway iceplant (Carpobrotus edulis)

Some iceplants have been intentionally used along highways and in sandy soils because they establish quickly, spread easily and control erosion. Unfortunately, these are some of the very characteristics that make these species invasive in coastal areas. This dense groundcover carpets over entire dune habitats along the coast from north of San Francisco all the way south to Mexico and on the Channel Islands. This iceplant increases soil salt content and blocks light from reaching other species – harming fragile native ecosystems, eliminating native plants such as beach strawberry, and rendering native nesting habitat (for shorebirds like the endangered snowy plover) inhospitable.

Non-Invasive ALTERNATIVES (just a few of many alternatives):

–          Non-invasive iceplant (Delosperma cooperi)

–          White trailing iceplant (Delosperma ‘Alba’)

–          Beach strawberry (Fragaria chiloensis / F. vesca)

–          Prostrate coyote bush (Baccharis pilularis)

INVASIVE: Mexican feathergrass (Stipa or Nassella tenuissima)

The first emerging invasive (i.e., not yet widely established in California open spaces, but likely to do so if left unchecked) to merit inclusion on the PlantRight list. Mexican feathergrass self-sows abundantly and is quick to spread out of its designated place in the garden. It is an extremely vigorous plant, which crowds out pasture species as well as native grasses in coastal areas.

In Argentina, where Mexican feathergrass is native, it is regarded as an unpalatable grass. The grass forms indigestible balls in the stomach of livestock and, if they are forced to graze the infected pasture, they may lose weight, get sick or even die. Mexican feathergrass can become dominant under continual heavy grazing pressure with a low frequency of high-intensity fire.

Non-Invasive ALTERNATIVES (just a few of many alternatives):

–          Blue grama grass (Bouteloua gracilis ‘Blonde Ambition’)

–          Autumn moor grass (Sesleria autumnalis)

–          White awn muhly (Muhlenbergia capillaris ‘White Cloud’)

INVASIVE: Pampas grass – Cortaderia selloana

If you walk along one of the many California landscapes invaded with pampas grass you won’t hear any bird songs. Pampas grass forms massive stands that crowd out the native plants that provide valuable habitat for birds and other wildlife. These tall plants burn quickly and at high temperatures, allowing flames to jump streams and land corridors that would normally act as barriers to the spread of wildfires. Each pampas plume produces up to 10,000 seeds each year.

Non-Invasive ALTERNATIVES (just a few of many alternatives):

–          Deer grass (Muhlenbergia rigens)

–          Foerster’s reed grass (Calamagrostis x acutiflora ‘Karl Foerster’)

–          Linheimer’s muhly grass (Muhlenbergia lindheimeri)

–          ‘Katie Belles’ and ‘Tropicbelle’ (Lomandra hystrix)


Garden Friendly Water Conservation Events at California area Home Depot stores May & June 2015

The Home Depot stores in Southern California

May 16

12975 W. Jefferson Blvd., Los Angeles CA 90066

12255 Pigeon Pass Rd., Moreno Valley CA 92557

3323 Madison St., Riverside CA 92504

14549 Ramona Ave., Chino CA 91710

May 30

5755 Mission Ave., Oceanside CA 92057

110 E. Sepulveda Blvd., Carson CA 90745

3150 Case Road Blvd. P., Perris CA 92570

695 E. Hospitality Ave., San Bernardino CA 92408

June 6

16005 Sierra Lakes Pkwy., Fontana CA 92336

1151 W. Lugonia Ave., Redlands CA 92374

12322 Washington Blvd., Whittier CA 90606

June 13

14603 Ocean Gate Ave., Hawthorne CA 90250

The Home Depot Stores in Northern California

May 16

2675 E. Bidwell St., Folsom CA 95630

Cover Photo Credit: KENPEI, GFDL,Creative Commons Attribution ShareAlike 2.1 Japan License

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