Invasive species are the second leading threat to wildlife and biodiversity, and they are expensive for public parks and agencies to remove. Although most garden plants are not a threat, more than half of invasive plants originally arrived through gardens and landscaping, so home gardening choices matter.
PlantRight, a statewide program to educate and inspire both the horticultural industry and the gardening public to prevent new introductions of invasive plants in California, earlier this year launched its campaign to encourage home gardeners in Southern California to avoid using invasive plants. It was created by the steering committee of California Horticultural Invasives Prevention Partnership (Cal-HIP) with the ultimate goal of protecting California wildlands and wildlife from invasive plants.
“Most of the plants used in gardens and landscaping do not invade wildlands and harm wildlife,” said Terri Kempton, PlantRight Project Manager at Sustainable Conservation. “But a few species can-and do-escape from cultivated areas into open landscapes and cause serious ecological problems. Fortunately, there are plenty of beautiful, safe alternatives to invasives, so it’s easy for gardeners to find plants that meet all their specific needs.”
“Invasive plants like Arundo donax, green fountain grass and iceplant cause significant harm to parks and natural areas throughout Southern California,” said Ruth Coleman, director of California State Parks. “They crowd out native plants, insects and animals. They are expensive to remove or control. Invasive plants can also make wildfires burn hotter and faster.”
The economic cost is as significant as the ecological cost: more than $35 billion per year nationally in eradication work and economic losses. In California alone, $85 million in taxpayer funds go to fighting invasive plants and animals every year.
In addition to being environmentally responsible, some noninvasive plants can offer additional benefits, such as drought resistance, lower fertilizer requirements and attracting wildlife. For people living in a fire zone, planting noninvasive fire-safe plants can help protect their homes and properties.
For each region of California, PlantRight’s steering committee identified the problem plants and noninvasive alternatives that will thrive in that area. For example, in Southern California, giant reed (Arundo donax) has invaded streams and riverbeds, crowding out the wide diversity of native plants and wildlife that rely on waterways to survive. Giant reed is also highly flammable and increases fire danger. Another invader in coastal areas is highway iceplant (Mesembryanthemum crystallinum). This dense groundcover carpets over entire dune habitats, eliminating native plants such as beach strawberry and endangering shorebirds like the snowy plover.
Following are case studies of invasive plants, and recommended alternatives.
Invasive: Arundo donax, giant reed
If you walk along one of the many California streams invaded with Arundo donax, or giant reed, you won’t hear any bird song. Arundo forms massive stands that crowd out the native plants that provide valuable habitat for birds and other wildlife. At least 10 protected animal species in California, including the least Bell’s vireo, suffer habitat loss to invading Arundo. These tall plants burn quickly and at high temperatures, allowing flames to jump streams that would normally act as barriers to the spread of wildfires.
Alternatives:Clumping Bamboos (Bamboos multiplex, B. oldhamii, Fargesia nitida); New Zealand flax (Phormium tenax cultivars)
Invasive: Pennisetum setaceum, Green fountain grass
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.
Alternatives: Blue Oat Grass (Helictotrichon sempervirens), Deer Grass (Muhlenbergia rigens), Sedge Cultivars (Carex spp.), California Fescue (Fectuca californica), Purple Fountain Grass (Pennisetum setaceum ‘Rubrum’)
Invasive: Iceplants , highway iceplant, crystalline iceplant (Mesembryanthemum crystallinum, 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 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. Iceplant increases soil salt content and blocks light from reaching other species-harming fragile native ecosystems, eliminating native plants such as beach strawberry, and endangering shorebirds like the snowy plover.
Alternatives: Noninvasive iceplant (Delosperma cooperi), Beach Strawberry or Woody Strawberry (Fragaria chiloensis / F. vesca), Myoporum Groundcover (Myoporum parvifolium ‘Prostratum’), Whorled stonecrop (Sedum ternatum)
-This article was provided courtesy of PlantRight.org