What Is an Ice Plant?

Ice plants consist of several species of succulents originally found in Africa and later imported to the United States. Often, ice plants can form large mats of vegetation; some of them are considered invasive species because they can choke out the native flora. They're found primarily along the West Coast and are especially common in Southern California, where ice plant is used as ground cover along freeways.

All ice plants are species in the family Aizoaceae, the fig-marigold family, although not all share the same genus. Common species of ice plant include Mesembryanthemum crystallinum, Carpobrotus chilensis, Carpobrotus acinaciformis and Carpobrotus edulis. C. chilensis, C. edulis and M. crystallinum are all considered invasive species. Ice plants are sometimes called sea fig or hottentot fig as well.

Ice plant is a perennial, meaning that it lives for more than two years. The leaves are large, crisp and succulent; the plant stores water in them to help protect against desiccation. All ice plants are ground cover and grow close to the ground. The color of the flowers varies; C. chilensis has purple flowers, while C. edulis has yellow or pink flowers and M. crystallinum has white flowers. M. crystallinum is covered in small transparent bladders so that the plant appears to be covered in frozen dew drops or a layer of ice.

Ice plants form a dense root system that makes them difficult to remove. If any part of the root system remains intact, the plant may resprout later. Ice plants prefer well-drained soils and lots of sun; they thrive best in a Mediterranean climate. They were originally imported to the United States from Africa, where their drought tolerance, tendency to form thick mats and ability to stabilize soil or sand made them a desirable choice as ground cover. M. crystallinum has the unusual ability to switch from one type of photosynthetic mechanism called C3 photosynthesis to another kind of photosynthesis, CAM photosynthesis, which is more common among cacti and other succulents.

Ice plant is largely restricted to the Pacific Coast, where the climate favors its growth. Its tendency to form mats is both a blessing and a curse because ice plants can choke out native vegetation. In California, for example, ice plant species like C. chilensis displace native plants that grow on dunes, among them several endangered species. It reproduces rapidly once established, and native competitors or herbivores appear to have little effect on its growth. While the ice plant is both beautiful and useful, its story demonstrates the need to exercise caution when introducing foreign plants to a new environment.