Advice to Grow By

UC Master Gardeners of San Diego County

Hotline (858) 822-6910
www.MasterGardenerSD.org

help@MasterGardenerSD.org

How to Keep Your Garden Safe from Invasive Plants

What is an invasive?
An Invasive Species is a species that is able to establish itself on many sites, may grow quickly and spread, disrupting natural
plant communities or ecosystems. Both plants and animals can be invasive. Some ornamental plants have been widely
planted only to become invasive over time. Animal pests such as the South American Palm Weevil have become big pests,
killing Canary Island palms from the Mexican border as far north as La Jolla and still advancing.
Invasive species not only have disastrous effects on natural ecosystems but have a large economic cost. The state of
California spends millions of dollars each year to try to control and remove invasive species. Home gardeners can also have
increased cost and work to control invasive pests, whether plant or animal.
Reducing fire hazard is another consideration. Native plants tend to burn more slowly while invasive plants tend to increase fire risk.

Why Does a Plant Become Invasive?

Native plants co-evolve with other animals in their ecosystem. One problem with invasive plants is that they are foreign to the new ecosystem and have no predators, parasites or diseases to hold them in check. Invasive plants reproduce early, fast and often. As a result, they outcompete native or other plants. They use up resources such as water, organic nutrients and space needed by other plants.

Another factor that makes invasive plants such a problem is they tend to have wider tolerance for different environmental
conditions. Invasive plants might tolerate conditions such as high temperatures that ornamental plants may not. Some invasive plants are just plain persistent. They keep coming back from pieces of roots left in the ground or from reseeding. Ever tried to get rid of nasturtiums, for example?

Where Do Invasive Plants Come From?

Invasive plants enter our region from a myriad of means. They can:

• hitchhike on all types of transportation vehicles.
• sneak in on packing materials.
• come under their own means, or via birds or animal fur, or, as in the case of the weevil, fly in.
• spread by wind, water, and wildfires.

Many plant species are brought here by people that want to grow a specific plant for cooking, cultural reasons or to remind
them of their previous home. They usually do not realize the damage that some plants can cause when brought into a new area.

Another source of invasive plant species is the nursery trade. New plant varieties are produced each year to help home gardeners grow plants successfully. Some of these become invasive so be aware and don’t buy an invasive plant.

Examples of Invasive Plants

California Invasive Plant Council lists species that have spread in San Diego County as invasive and discourage gardeners from planting them.

Here are a few common invasive plants from their list:

• Acacia species
• Brazilian Pepper Tree, Schinus terebinthefolius
• Butterfly bush, Buddleja davidii
• Eucalyptus species
• Feather grasses, Pennisetum species, all species and varieties
• Garden Nasturtium, Tropaeolum majus
• Hottentot fig/Ice plant, Carpobrotus edulis
• Mexican fan palm, Washingtonian robusta
• Mustard species
• Pride of Madeira, Echium candicans

But there are many more invasive species.

What Can You Do to Prevent Invasive Species?

• Learn which plants are invasive in your county. Ask the nursery staff if the plant is invasive in your area. This also helps educate the nurseries that a gardener does not want invasive species in their garden.
• Do not bring plant/seeds from other areas.
• Support organizations that work to remove invasive species.

Resources for further information

• California Invasive Plant Council, See: “Plants A to Z”
• San Diego Chapter of the American Society of Landscape Architects
• City of Carlsbad: Identification Guide: Plants and Animals
• Bossard, Randall and Hashovsky: Invasive Plants of California’s Wildlands

The Master Gardener Association of San Diego County supports the University of California Master Gardeners of San Diego County. UCANR is an equal opportunity provider and employer.