Highway Ice Plant spreads readily over time. It forms mats that work well as a ground cover, and overwhelms most other plants. Some field grasses manage to establish roots among the ice plants. (Contributed)
This column’s title includes one of the common names of a plant that has become a significant problem throughout coastal California and particularly in Santa Cruz, where it has invaded the West Cliff Drive environment.
Other common names for our featured plant include Hottentot Fig, Sour Fig, Sea Fig, Cape Fig and Pickleweed. The “fig” term refers to the plant’s fruiting capsule, which resembles the true fig. In South Africa, the plant’s name in Afrikaans name is “vygie” meaning “small fig.”
The botanical name for this plant is Carpobrotus edulis, a member of the Fig-Marigold plant family, the Aizoaceae, which is a large family of flowering plants including 135 genera and about 1,800 species. They are most commonly known as ice plants. Glistening epidermal bladder cells give these plants an icy appearance.
Ice plants have common characteristics: succulent leaves, shallow roots, daisy-like blossoms, and spreading or trailing growth patterns. In addition, deer and other mammals eat the plant’s edible leaves and fruiting capsules and spread the seeds through their droppings.
The most common blossom color for Highway Ice Plant is pale yellow. The leaves are triangular in form and up to 4 inches long. (Contributed)
Our featured plant, Carpobrotus edulis, spreads more aggressively than other Ice Plant species, earning a reputation as an invasive species. A close relative, C. chilensis, hybridizes readily with C. edulis, and has the same reputation as an invasive plant.
Edilis has been tagged as “Highway Ice Plant,” because it has been used in California since the early 1900s to stabilize soil and reduce erosion along railroad tracks and highways. Until the 1970s, thousands of acres were planted with C. edulis. Caltrans still installs this plant along highways, as shown by an internet search, but other state agencies work to remove it.
For example, the California Department of Parks and Recreation states that, “Non-native invasive plants pose a serious threat to native ecosystems,” lists the ice plant as one of the worst exotic plant invaders, and its resource management policies “direct the Department to preserve and restore indigenous plants and animals, while systematically removing populations of exotics in wildland settings.”
Some blossoms are pink. (Contributed)
Another example: the California Department of Fish and Wildlife states, “Because (ice plant) is a coastal invader, it competes with many endangered, threatened and rare plants. It is important to follow iceplant removal with rehabilitation of the area because it is easy for iceplant to re-establish in bare soil. Although iceplant can be attractive, it is important not to plant it in areas where it may become invasive.”
Avoidance or removal of Highway Ice Plant is also recommended by private groups, e.g., the California Invasive Plant Council and the California Native Pant Society.
In Santa Cruz, Highway Ice Plant (or Pigface, as it has been called) is well established along West Cliff Drive. Historian Ross Gibson wrote that, around 1963, “The cliffs were planted with dune plants like “mesembryanthemum” or ice plant. This provided drought-tolerant flowers and greenscape, fire suppression of volatile grasses, cliff-soil conservation, and erosion control. It was adopted by women’s clubs at the turn of the century to expand the floral aesthetic.”
The Sea Fig has become established in separate areas along West Cliff Drive. (Contributed)
During the following 60 years, these plants have spread to become the most prominent vegetation on West Cliff Drive, and have invaded Lighthouse Field State Beach.
These plants bloom from April to late summer. C. edulis’s flowers are generally pale yellow flowers and sometimes pink. C. chilensis has rose-purple blossoms, as seen in separate areas. Because these two species hybridize readily, as noted above, combinations may be seen.
The flowers are attractive, admittedly. Other less invasive ice plant species, particularly Delosperma and Lampranthus, have jewel-tone blossoms and are more suitable for garden use.
The city of Santa Cruz has adopted “The West Cliff Adaptation and Management Plan” (April 2021), which states, “The greatest enhancement opportunities for the terrestrial portion of West Cliff are restoring native habitat by removing invasive iceplant followed by replanting with a diverse palette of locally sourced native plant species. Restored habitat may support an increased biodiversity of resident and migratory fauna in less than one year. The long-term goal should be to remove iceplant throughout West Cliff.”
The Sea Fig, a close relative of the Highway Ice Plant, has similar leaves, and bright magenta flowers with yellow anthers. (Contributed)
In 2022, Santa Cruz Parks and Recreation’s Superintendent of Parks Travis Beck stated that staff removed a section of ice plant from the area between the path and the road down near Chico Avenue and replanted it with native coastal plants. The department has an annual project to cut back the ice plant where it overgrows the path and curb. This is more of a traffic maintenance process than a restoration effort.
The department is also developing more specific plans for the West Cliff landscape, including ways to complete ice plant removal and develop restoration plantings.
The city of Santa Cruz is focused currently on the West Cliff Resiliency and Accessibility project, so replacing the ice plant with native plant species will take its place on the priority list, but this habitat restoration process is clearly on the list.
Removal methods include mechanical control by digging or bulldozing, chemical control with glyphosate herbicide, or biocontrol with the South African Scale Insect (Pulvinariella mesembryanthemi), a specialized herbivore. Many gardeners would favor the bulldozing option.
One important aspect of this scheduling is State Parks’ goal to “preserve and restore indigenous plants and animals.” The state’s pursuit of that goal might need to include the city’s prior removal of the C. edulis that has been spreading into Lighthouse Field State Beach.
Wayne Kihei and others on the Santa Cruz Parks and Recreation West Cliff Ice Plant Hit Team removing ice plants from a West Cliff Drive walkway in May 2022. After the plants have been cut back, they could re-root on bare soil, so must be removed. (Santa Cruz Parks and Recreation/Contributed)
We will monitor that process.
Mark your garden calendar
The Monterey Bay chapter of the California Rare Fruit Society has announced its first-ever “Fruit-a-Palooza” event for June 10.
Advance your knowledge
For more on this column’s main topic, visit Debra Lee Baldwin’s online talks, including “Succulent Ice Plants for Your Garden” (tinyurl.com/2472npr7) and “Recognize and Avoid Weedy Succulents” (tinyurl.com/yc228xyj).
Enjoy Ice Plants only in your garden.
Tom Karwin is a past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and Lifetime Member of the Monterey Bay Area Cactus & Succulent Society, and a Lifetime UC Master Gardener (Certified 1999–2009). He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society. To view photos from his garden, https://www.facebook.com/ongardeningcom-566511763375123/ . For garden coaching info and an archive of On Gardening columns, visit ongardening.com. Email your comments or questions to email@example.com.