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Invasive Plant Species

What is an invasive species?

An invasive species is any non-native species whose introduction causes (or is likely to cause) economic or environmental harm or harm to humans, animals or native plant health.

What does it take to be invasive?

May contain: plant, flower, blossom, geranium, and acanthaceae
periwinkle (Vinca major)

It takes several characteristics for a plant to have the potential to become invasive:

  1. Fast growth
  2. Rapid reproduction
  3. High seed dispersal ability
  4. Tolerance of a wide range of environmental conditions
  5. Ability to outcompete native species for nutrients, light, space, etc.

The Cost of Invasives

May contain: plant, blossom, and flower
Yellow Starthistle (Centaurea solstitialis)

Across the United States, it is estimated that invasive species (both plants and animals) cost $138 billion annually.  This figure includes the cost of control measures as well as the cost associated with loss of tourism and recreational activities.  In California alone, $82 million is spent annually on control, monitoring, and outreach activities.  The total cost of invasives in the state is estimated to be billions of dollars.

Why should we care about invasive plants?

Invasive plants can affect our everyday activities and the health of our watersheds. 

May contain: plant and agavaceae
Giant Reed, False Bamboo (Arundo donax)
  • Some invasive plants consume enormous quantities of water.  This water is lost to wildlife, agriculture and the drinking supply.
  • Invasives can clog creeks, reducing their water-carrying capacity and increasing the risk of floods during winter storms.
  • Some invasives generate higher fuel loads than native plants.  When these plant species invade, wildfires can be more frequent.
  • Invasions can cause land values to drop and management is often costly.
  • They can blanket waterways, trails, and scenic landscapes, making boating, hiking and biking difficult, and lowering the land's value for photography and wildlife viewing.
  • Invasive plants can crowd out crops and livestock forage.
  • They can significantly degrade wildlife habitat.  Nationally, invasive species are the second greatest threat to endangered species, after habitat destruction.

What can you do?

There are several things that you can do at home to help minimize invasive species populations in southern California.

May contain: person, human, tree, plant, vegetation, bush, conifer, outdoors, and nature
Salt cedar (Tamarix sp.)
  • Avoid using known invasive plant species in gardens and landscaping.
  • Check out your local Weed Management Area (WMA) and report infestations.
  • Educate others about invasive plants.
  • Encourage your local nurseries not to sell invasive plants.
  • Volunteer with local groups to remove invasive species in your watershed.
  • Participate in local eradication programs to support the health of your watershed.

Your local Weed Management Area

The Santa Margarita and San Luis Rey Watersheds Weed Management Area (WMA) was formed to provide support, coordination, and funding for management of non-native invasive plants and restoration of native riparian habitat within the Santa Margarita and San Luis Rey watersheds in San Diego County.

The WMA is a valuable community resource. Report any invasive plant infestations to your WMA.

Invasive Plant Species Resources