Sustainable Conservation - Partnership to Prevent Invasive Plants

Notes from the Project Manager

Hello, and welcome to the fall 2005 edition of our Friends of the Partnership newsletter! Sustainable Conservation is pleased to share an update on our collaborative effort to address the unwanted spread of horticultural plants into open places and wildlands. Members of our steering committee represent the horticultural and environmental communities, and they continue to address invasive plants that are available for gardening and landscaping. Together, they are identifying non-invasive alternative plants and creating strategies for communicating their findings.

This newsletter is designed to share the progress of the California Partnership to Prevent Invasive Plant Introductions through Horticulture (Cal-PPIPIH). We want to keep you informed, engaged, and aware of invasive plant issues in California. For a chance to participate in our collaborative process, please see the request for feedback below. Your comments and questions are always welcome, and we invite you to share your own projects and news with us. Events, publications, and links will be included in each edition of the newsletter. For contact information, see the bottom of the page.

Enjoy the season, and keep in touch!

Terri Kempton
Project Manager, Cal-PPIPIH

News from the Steering Committee

In September, the Cal-PPIPIH Steering Committee visited invaded wildlands in Marin County to observe first-hand the scope of the problem and the amount of time, energy, and funding that is being devoted to controlling and eradicating escaped horticultural plants. Between the 800 acres of French broom on Marin County Water District lands, the barrage of garden plants invading Pt. Reyes National Seashore, and the extent of resources that go into managing these problems, Steering Committee members were thoroughly impressed by the magnitude and extent of the invasive plant problem.

*Steering Committee members on Mt. Tam*

The following day, the Steering Committee began development of a toolkit of materials and strategies to educate the horticultural industry and the gardening public about invasive plants to avoid and alternative plants that can be used safely. The group discussed the best way of communicating clear messages to nurseries, landscapers, gardeners, and other members of the horticultural community. Some specific outreach opportunities are:

creating or supporting an on-line database of information about invasive plants for wholesale/nurseries
generating brochures and posters for placement in retail locations
Master Gardener teaching tools for information dissemination

Members of the Committee are dedicated to engaging their colleagues in the process of identifying invasive plants and their alternatives. Before the next meeting in December, Cal-PPIPIH members will ask for feedback and suggestions from their stakeholder communities to ensure a transparent process that will help the industry prevent new and continuing horticultural plant invasions.

We Need Your Input!

The Cal-PPIPIH Steering Committee has generated a preliminary list of invasive plants that have horticultural value, for which we are considering recommending the substitution of non-invasive alternatives. These recommendations would be sensitive to regional issues and differences in plant invasiveness. Working collaboratively, Cal-PPIPIH members are developing strategies to support the horticultural community in a successful and profitable transition to non-invasive products. As a part of this effort, we plan to develop a toolkit of outreach and education materials for the horticultural community. The members of Cal-PPIPIH are seeking your feedback on this process and the preliminary list of plant species under consideration, as listed below. We would like very much to hear your responses to the following questions:

What are the difficulties and benefits you would face in making a transition from one of the listed plants to non-invasive alternatives?
What additional information would you need to replace any of the plants on the list with non-invasive alternatives?
How much time would you need to make a transition from one of the plants listed here to a non-invasive alternative?
What alternative plants can you recommend for the plants listed here?

The invasive plants now under consideration by Cal-PPIPIH for substitution with non-invasive alternatives are:

Arctotheca calendula, or fertile capeweed, has invaded natural habitats in areas of coastal prairie (e.g., Humboldt County) and coastal scrub (e.g., Monterey County). Fertile capeweed forms dense mats that crowd out all other plants.
Arundo donax, or giant reed, crowds out native plant species along waterways and is a fire and flooding hazard. Arundo populations can spread rapidly, doubling as quickly as every 10 years.
Elaeagnus angustifolia, or Russian olive, invades arid areas (e.g., San Joaquin Valley, southern Sierra Nevada and parts of the Mojave Desert), drains water resources and increases fuel loads for wildfires.
Myoporum laetum, commonly referred to as myoporum, forms monocultures and displaces native vegetation. It is potentially toxic to wildlife and livestock and has invaded areas along the south and central coast.
Sapium sebiferum, or Chinese tallow tree, grows faster than native vegetation and can establish and proliferate under a variety of environmental conditions. It has invaded areas in the Sacramento Valley, the San Francisco Bay Area, and along the American River Parkway. It has become a problem in areas of other states similar to California (e.g., coastal Texas), indicating a serious invasion potential.
Sesbania punicea, also known as scarlet wisteria, invades riparian areas and forms dense monotypic stands. It has invaded 60% of the 44 miles of creek bed in Sacramento and Placer Counties. The tree is highly toxic to animals and has poisoned birds that try to eat their seeds.
Tamarix ramosissoma, or salt cedar, has invaded the river systems of arid California. This tree drains water tables, deposits salt in the soil, increases flooding, and creates a fire hazard.
Vinca major, or periwinkle, can form a dense carpet where it excludes native herbs and out-competes native vegetation. It has invaded along streambanks and in humid areas, including Garrapata State Park and Pt. Reyes National Seashore.
Aquatic invasive plants, including Eichhornia crassipes (water hyacinth), Egeria densa (Brazilian waterweed), Myriophyllum aquaticum (parrot's feather), and Elodea canadensis (common waterweed), are invasive in wetlands, sloughs, and ponds across the state. These plants can completely fill a water body, altering water flow and temperature, blocking out native plants and the organisms that rely on them.
Members of the broom family, including Cytisus scoparius (Scotch broom), Cytisus striatus (striated broom), Genista monspessulana (French broom), Retama monosperma (bridal veil broom), and Spartium junceum (Spanish broom), have invaded hundreds of acres across the state and are identified as one of the worst weeds by The Nature Conservancy. Their prolific seed bank can live in the soil for decades, making these plants particularly difficult to remove. Please note, this list does not include "Sweet Broom;" Cal-PPIPIH has no information indicating that it is invasive in California's wildlands.
The ice plants, Carpobrotus edulis (highway iceplant) and Mesembryanthemum crystallinum (crystalline iceplant), are an invasive problem along the California coast. These plants take over coastal dunes eliminating prime bird nesting habitat, and release salt into the soil, rendering the area uninhabitable to native plants and animals.

Related News

The California Invasive Plant Council (Cal-IPC) held its 14th annual symposium from October 6-8 in Chico, California. The gathering, "Prevention Reinvention: Protocols, Information, and Partnerships to Stop the Spread of Invasive Plants," attracted more than 350 attendees and featured 40 talks, 24 posters, and four field trips. In several of the eight break-out sessions, the role of horticulture in both introducing and preventing the introduction of invasive plant species was discussed. An entire day preceding the symposium was dedicated to hands-on training in wildland weed removal techniques.

Next year's symposium will be in Sonoma County from October 5-7, 2006. It will be a great chance for restoration professionals, volunteers, and researchers to discuss the latest in invasive plant biology and management. To learn more, visit the Cal-IPC web site at www.cal-ipc.org.

*Morning session of the Cal-IPC 2005 Symposium*

Featured plant

By our next newsletter, Cal-PPIPIH will have some non-invasive alternative plants to recommend in place of invasive species. As the Partnership continues the collaborative process to prevent plant invasions, this section of the newsletter will showcase our findings and suggestions. Each season we will highlight a non-invasive plant to inspire the gardening community to explore alternative planting options. Stay tuned for more information.

Recommend a friend!

If you know of anyone that would like to learn more about the Partnership, please let us know! Help our network of Friends expand by referring colleagues or organizations that are concerned about horticultural prevention of invasive plants. They will receive an email with a link to the newsletter.