Many popular ornamental plants in California have become invasive, spreading beyond gardens and causing harm to local ecosystems. These plants often escape through seed dispersal or aggressive root systems, allowing them to establish themselves in the wild and outcompete native species.
Invasive plants can be spread unintentionally by people when seeds attach to clothing, pets, equipment, or vehicles. Some invasive species were introduced on purpose for landscaping, erosion control, or as windbreaks but later escaped into natural areas. Once established outside of gardens, these non-native ornamentals can grow quickly and dominate their surroundings.
Only a small percentage of introduced plant species become invasive, but those that do share traits such as rapid reproduction, adaptability, and a lack of natural predators. Scotch broom (Cytisus scoparius) is an example of a plant brought to California for ornamental use and erosion control that has since become highly invasive. Its fast growth and prolific seed production make it difficult to manage; currently it infests over 700,000 acres in the state.
Organizations like the California Invasive Plant Council (Cal-IPC) are working to raise awareness about invasive ornamentals and encourage the use of non-invasive alternatives. Cal-IPC maintains an inventory list identifying plants with significant ecological impacts and high potential for spread. The list also highlights “watch” species at risk of becoming problematic in the future.
A majority of the species listed by Cal-IPC were intentionally introduced—about 63% for uses such as landscaping or agriculture—with nearly 80% entering through nurseries as ornamental plants. While some are regulated by state agencies like the California Department of Food and Agriculture (CDFA), many invasive ornamentals remain legally available for sale in nurseries across California.
Residents are encouraged to research which ornamentals are considered invasive before planting new gardens or landscapes. They should remove any spreading invasives from existing yards and consider replacing them with native or non-invasive alternatives suited to local conditions. Resources such as university extension offices or native plant societies offer guidance on appropriate choices.
Examples of common invasive ornamentals include big periwinkle (Vinca major), calla lily (Zantedeschia aethiopica), and pampas grass (Cortaderia selloana). Each has been shown to displace native vegetation due to aggressive growth habits. Alternatives recommended include douglas iris for ground cover instead of periwinkle, bush anemone instead of calla lily, and giant wildrye instead of pampas grass.
UC Master Gardener volunteers are available for advice on managing garden invasives. Reports about problem species can be made through County Agricultural Commissioner’s Offices or local UC Cooperative Extension Offices.
According to the U.S. Environmental Protection Agency (https://www.epa.gov/watershedacademy/invasive-non-native-species), invasive non-native species pose significant threats by disrupting habitats and reducing biodiversity.
Sources:
Bossard, C. (1996). IPCW Plant Report – Cytisus scoparius.
US Environmental Protection Agency (https://www.epa.gov/watershedacademy/invasive-non-native-species)
