Delairea odorata, commonly known as Cape Ivy, is a perennial climbing vine that originated in the moist mountain forests of South Africa. It was introduced as an ornamental plant in the mid-19th century, and has since spread extensively, establishing itself in diverse environments worldwide.
Identifying Cape Ivy
Its leaves are glossy green and somewhat fleshy, typically 3 to 8 centimeters long and wide. They are broadly deltate or “ivy-shaped” with five to nine pointed lobes, sometimes displaying a purple tinge, and emit a medicinal scent when crushed. These leaves are arranged alternately along the stems, often with small, kidney-shaped stipules at their base.
It grows as a climbing or trailing vine, with stems reaching up to 9 meters long. Younger stems are thin and purplish, becoming woody with age. Cape Ivy produces small, yellow, daisy-like flowers, clustered at the tips of branches with a sweet fragrance. These flowers usually appear in dense clusters during late winter and early spring.
Why Cape Ivy is a Problem
Cape Ivy rapidly spreads, forming dense mats up to 30 centimeters thick that can smother and shade out native vegetation, shrubs, and even trees. This dense cover prevents the germination and growth of other species, reducing biodiversity within affected ecosystems. Its climbing nature allows it to ascend into tree canopies, potentially breaking branches and altering forest structure.
The plant reproduces vegetatively from small stem or root fragments; even a one-inch piece with a node can generate a new plant. This makes it difficult to manage, especially in riparian areas where water currents easily transport fragments downstream, leading to new infestations. Cape Ivy has a shallow root system, typically extending only up to 10 centimeters deep, which can exacerbate soil erosion, particularly along stream banks.
Cape Ivy contains toxic compounds. Its leaves contain pyrrolizidine alkaloids, which are liver toxins. These compounds can be harmful to livestock if ingested and are toxic to mammals, spiders, and fish, potentially affecting aquatic organisms when plant material enters waterways. The presence of these toxins limits the plant’s palatability to wildlife.
Controlling and Removing Cape Ivy
Managing and removing Cape Ivy requires a persistent and integrated approach. Manual removal is effective for smaller infestations, involving hand-pulling or digging to extract the plants. It is important to remove all root fragments and stem pieces, as even small remnants can resprout and lead to reinfestation. Collected plant material should be disposed of by bagging it or allowing it to dry out completely off the ground to prevent re-rooting.
Mechanical methods, such as cutting the vines at ground level, reduce the plant’s energy reserves and prevent seed production. Mowing is generally not recommended because it can fragment the plant, inadvertently spreading viable pieces and exacerbating the problem. For large, dense patches, the plant can be rolled up like a rug after cutting the stems at ground level, which helps in accessing and treating resprouts.
Chemical control options include herbicides like glyphosate and triclopyr. Glyphosate is a non-selective herbicide, affecting any plant it contacts, and is often applied as a foliar spray or through wiper applications. Triclopyr is a selective herbicide that targets broadleaf plants, making it suitable for areas where desirable grasses are present. Clopyralid is another selective broadleaf herbicide effective against Cape Ivy.
Apply herbicides when plants are actively growing, such as late summer or early fall for glyphosate, or when new growth appears in spring for triclopyr. For vines growing on trees, stems can be cut at waist height, pulled away from the tree, and then sprayed with herbicide, or the cut stumps can be immediately painted with a suitable herbicide. Always adhere to product labels for application rates, safety precautions, and guidelines, including the use of surfactants to improve herbicide penetration. Regular monitoring and repeat treatments are important for long-term management and preventing re-establishment.