- A beautiful creeper known as the cat’s claw vine has become something of a springtime attraction in Sri Lanka, but its explosive growth could turn it into an invasive species.
- The exotic species, introduced as an ornamental plant from the New World, can grow up to 30 meters (98 feet), enabling it to reach even the canopies of tall trees, posing huge problems to host trees and smothering smaller plants.
- Other countries around the world, including the U.S., have categorized it as an invasive alien species — something Sri Lanka may have to consider once the plant begins to pose a threat to the native vegetation.
- This post is a commentary. The views expressed are those of the author, not necessarily Mongabay.
During the middle of March each year, the ornamental cat’s claw vine (Dolichandra unguis-cati) bursts into bloom in Sri Lanka, and this year is no exception.
The entire creeper gets covered in pretty golden yellow blooms and becomes a sight to behold. The largest concentration of these vines is found in Peradeniya, in the central district of Kandy, mostly within the premises and the vicinity of the University of Peradeniya.
People look forward to this spectacle during the flowering season, as evident from the numerous photographs, social media posts and stories published and even poems that refer to the unparalleled beauty of the flowering vines.
Exotic plant species
The cat’s claw vine is an exotic species that was introduced to Sri Lanka as an ornamental plant. It is native to tropical America and the Caribbean islands.
It is a long trailing creeper or vine that can grow to lengths of even 30 meters (98 feet) which makes it possible to reach the canopies of taller trees. It produces numerous branches that in turn give rise to thin, hanging branches that dangle down from the host like a green cascade.
The leaves are comprised of two small leaves, and a third modified into a three-pronged clasping tendril, shaped somewhat like the nails in the paws of a cat, which gives the creeper its name: cat’s claw.
The flowers are borne from the nodes of the leaves and are large and have a short tubular corolla that ends in five petals. The flowers are a bright golden yellow and are quite conspicuous even from a distance. They virtually cover the smaller vines, which shed most of their leaves during flowering, enhancing the effect made by the flowers. It has not been observed producing seeds in Sri Lanka.
However, this fast and profusely growing vine poses many problems for the host trees. The mass of vines adds a considerable weight, and branches of trees and even entire small trees have collapsed under the weight of this vine. The smaller vines cover the branches, which makes the branches defoliate and eventually die. It leads to the weakening of the trees, which may gradually die. There are instances where a whole tree has died, after being covered and smothered by the cat’s claw vines. Even taller trees are not safe from this vine, as it can easily reach the canopy of most and thereafter spread over, smothering the canopy. Since the vine produces large numbers of leaves, the leaves that are shed form a thick mat of fallen leaves that can prevent the germination of seeds and cover the smaller plants that grow on the floor.
The cat’s claw vine has become an invasive species in a number of countries; it has been placed on the list of Invasive Alien Species (IAS) prepared by the IUCN’s Invasive Species Specialists Group (ISSG). It is considered an IAS in U.S., Australia, Uganda, Kenya and some of the Pacific islands.
Despite the global trend, this species is not yet considered an invasive alien species in Sri Lanka, and is not extensively cultivated here, except for the few well-known localities where it has occurred for a long time.
It is my observation that the creeper readily takes root when in wet soil and can be easily propagated through cuttings made from the thin, hanging vines. It grows quickly, needs little care and can cover the ground and grow if a suitable host tree is found. It can also hop from canopy to canopy or from tree to tree, if there are closely placed branches.
The extensive growth habits and the large space needed for it to flourish, together with the habit of it covering up trees, have dissuaded most people from even trying to cultivate it in their home gardens. This is fortunate, as it has prevented this plant from escaping into the wild.
The creeper has been often used by some to cover pergolas, rooftops and trellises in buildings and other such urban green spaces. This makes it possible for the uprooted vines or pruned branches to find their way to natural habitats.
As beautiful as it is, this is yet another exotic ornamental plant in Sri Lanka with the potential to become an IAS in the future, if adequate care is not taken of the existing population.
This highlights an existing need to a need place it in the category of a potential invasive species, and to conduct a risk assessment, in order to assess the degree of risk posed by it and to inform what kind of preemptive actions may be needed, or not, to prevent it becoming a problem in the future.
Jagath Gunawardana is a Colombo-based environmental lawyer, lecturer and naturalist.
Banner image of a flowering cat’s claw vine, courtesy of Jagath Gunawardana.
