In the early 1900s, California planted the ice plant on railway embankments as a means to control erosion, and the California Department of Transportation (Caltrans) later planted it in roadside areas. This succulent plant, known as Carpobrotus edulis, is native to the coastal regions of South Africa, which has the same type of climate as coastal California. The ice plant has also been a popular ornamental plant for many years and is still available in nurseries.
The California Department of Fish and Wildlife states that the plant grows fast and has been invasive in coastal California, ranging from areas above Humboldt County to as far south as Baja California. According to CDFW, once introduced, the plant forms a thick and extensive carpet that kills competing plants and modifies the soil composition. Due to being an invasive coastal plant, it competes with many endangered, threatened, and rare species.
Ice plant takes over dune habitats at Point Reyes
The National Park Service article has recorded the invasion by monitoring its own habitat. In this article, the ice plant, otherwise known as sea fig, is described as a perennial, mat-forming succulent that propagates by means of seeds and colonies. Ice plant may grow up to more than 3 feet in diameter in a year. During the monitoring period, eight of the 12 dune plots were invaded by ice plant.
Deep Dive
Why is ice plant considered invasive in coastal California?
How can ice plant infestations be removed?
What can I plant instead of ice plant for erosion control?
Walker links the plant to wider ecological effects. Ice plant alters the natural movement of sand in dune habitats, which changes the environment and reduces species diversity. Several sites had large colonies with multiple layers of dead material from previous years, so dense that nothing else could grow beneath it. The plant also has specialized structures that hold salt and release it into the soil when it dies. That prevents native species such as bluff lettuce (Dudleya farinosa) from establishing and results in a monoculture. Bluff lettuce is not currently listed as threatened or endangered, but only two of the dune plots at Point Reyes National Seashore have small populations of it.
{{/usCountry}}Walker links the plant to wider ecological effects. Ice plant alters the natural movement of sand in dune habitats, which changes the environment and reduces species diversity. Several sites had large colonies with multiple layers of dead material from previous years, so dense that nothing else could grow beneath it. The plant also has specialized structures that hold salt and release it into the soil when it dies. That prevents native species such as bluff lettuce (Dudleya farinosa) from establishing and results in a monoculture. Bluff lettuce is not currently listed as threatened or endangered, but only two of the dune plots at Point Reyes National Seashore have small populations of it.
{{/usCountry}}The article says removal is challenging. The ice plant flowers throughout the year, with each fruit producing up to hundreds of seeds, which easily spread after the removal or application of herbicides on the parent plant. Seasonal “Thursday Weeders” volunteer events are held twice a month at Abbott’s Lagoon by the Point Reyes National Seashore Association and the park service to remove ice plant and other problem plants such as European searocket and European dune grass.
Recommendations by the authorities
According to CDFW, ice plants should not be planted in areas where they might become invasive, and native alternatives are recommended. An example of such a plant is the purple sage (Salvia leucophylla). This is an evergreen shrub that reaches a height of 3 to 6 feet and produces light purple flowers from May to July. According to the agency, it does not need any watering once planted and is useful for erosion control.
For existing infestations, the department says ice plant is shallowly rooted, so it can be controlled manually, and removal can serve as a volunteer day for student groups. Because the plant is so widespread, however, only small infestations can realistically be tackled at one time. The department adds that removal should be followed by rehabilitation of the area, since ice plant can easily re-establish in bare soil.
Native succulents are under their own set of pressures. The park service says there are 26 native Dudleya species in California, 10 of which are listed as threatened or endangered under the Endangered Species Act. In some poaching cases, between 50 and 800 plants have been uprooted from the wild areas of Mendocino County. On September 28, 2021, California Gov. Gavin Newsom signed AB 223, making it unlawful to uproot, remove, harvest, or cut dudleya from state or local government land, or from private property without written permission, subject to the law’s exceptions.