In the 1950s, California brought in Cape ivy as an ornamental vine; it spread across 500,000+ acres, cutting native seedling variety by as much as 95%

Cape ivy was introduced to California for its ornamental value, but the fast-growing vine eventually became a threat to the state’s coastal forests and streamside habitats. Its dense foliage can cover shrubs and trees, block sunlight and prevent native plants from regenerating. Once established, it can be difficult to remove because even small fragments of its stems may grow into new plants.

According to the California Invasive Plant Council (Cal-IPC), Cape ivy (Delairea odorata) was introduced to Marin County and Golden Gate Park in the 1950s for landscaping and became naturalised within about a decade. The council’s assessment reported that the plant occupied more than 500,000 acres in California. Its spread has raised concerns because research has documented substantial reductions in native plant diversity and seedling abundance in invaded habitats.

From ornamental plant to invasive vine


According to a study published in Biological Invasions, Cape ivy (Delairea odorata), native to South Africa, was introduced to the eastern United States in the 1850s as an ornamental plant. It was later collected growing wild in Berkeley, California, in 1892 and had become invasive in the San Francisco Bay Area by the 1960s. The vine thrives in shady, moist environments, including stream banks and fog-influenced coastal forests.

It has also spread into habitats such as oak woodlands, coastal scrub, grasslands and seasonal wetlands, where its dense growth can cover existing vegetation and compete with native plants for light and space. Cape ivy reproduces via creeping stems known as stolons that have the ability to take root at their nodes. Underground stems aid in its survival, while detached segments may regenerate when placed in appropriate environments. These segments may be accidentally transported from one area to another by water, gardening tools, and landscaping activities.

What research found about native plants

Cape ivy can alter the structure of plant communities by spreading across the ground and climbing over shrubs and trees. Its thick foliage reduces the amount of light reaching plants below, making it harder for native seedlings to establish and survive. A study by Alvarez and Cushman, published in Ecological Applications in 2002, examined Cape ivy in three coastal California habitats: coastal scrub, willow riparian forest and alder riparian forest. The researchers found that plots invaded by Cape ivy contained 36% fewer native plant species than uninvaded plots. Native seedling abundance was also 88% lower in invaded areas, while non-native seedling abundance was 92% lower.

Additionally, the scientists carried out a field study in which Cape ivy cover was decreased. After two years of this decrease, there was a 10% increase in the diversity of native plants and an 86% increase in seedlings. These results suggested that removal of this vine could help the native vegetation to regenerate, though it did not mean that all plant communities would react to the change in the same way. Apart from affecting vegetation, the plant contains toxins that can harm animals. When Cape ivy is present in waterways, it can pose a threat to fish. In addition, the dense growth of Cape ivy near streams can lead to erosion.

Why controlling Cape ivy is difficult

Researchers have also looked at biological control as a way of keeping Cape ivy in check. One candidate is the Cape ivy shoot-tip galling fly (Parafreutreta regalis), a small insect native to South Africa. It lays its eggs in the plant’s growing shoots, causing galls that can weaken the vine. Tests found that the fly was highly specific to Cape ivy, with no gall formation on the 93 other plant species examined. The insect was first released in California in 2016, with further releases carried out at other sites, including southern California in 2018.

The aim of biological control is not to wipe out established Cape ivy patches overnight, but to gradually reduce the plant’s growth and spread. Its success will depend on whether the fly can establish itself and have a noticeable effect under natural conditions. Cape ivy’s history is a reminder that plants introduced for their ornamental appeal can behave very differently once they escape gardens and enter native habitats.