It’s been a while since we’ve featured a parasitic plant species. Parasites are often thought of negatively, due to their incursion on the livelihoods of other species. However, they’re undeniably fascinating! This large parasitic climber is Cassytha melantha, also known as coarse dodder-laurel.
The scale of this picture may be deceptive, as the vine seems to be at least a few centimeters thick as it wraps around the trunk of a tree. It is actually 1-4 mm thick (~0.1 in.), and wrapped around a small stem of Acacia mearnsii. Native throughout much of southern Australia, coarse dodder-laurel (and other species of the tree- or shrub-smothering Cassytha) is a common sight in the region. Cassytha melantha is among the largest of the dodder laurels. Unlike most Cassytha species, it primarily uses eucalypts as host plants (today’s photograph being an exception).
Seed dispersal is achieved by birds eating the small green fruits and passing the seeds through their gut. If the seeds land in an appropriate location near a host plant, the initial stem of this species will rotate until it finds its host, after which it climbs and attaches itself to smooth bark. Sap-sucking discs allow coarse dodder-laurels to both stay attached to the host plant’s bark and acquire nutrients by penetrating the cambium layer. Eventually, the original portion of the stem that germinated dies off, leaving the dodder-laurel plant completely dependent on its host.
The name dodder is often associated with species of Cuscuta, which are similar parasitic twiners in a different family. The laurel part of the name is due to the placement of Cassytha within the laurel or bay family, the Lauraceae. Cassytha is related to Cuscuta etymologically, originating from the Greek word kasytas. The specific epithet melantha, comes from the Greek words melas (black), and anthos (flower), referring to the small black hairs on the calyx of the flower. These flowers emit a pleasantly-fragrant perfume, which attracts a number of pollinators. Leaves, when present, are small, red, and scale-like.
Many additional photos of coarse dodder-laurel, including one of its smothering nature, can be seen on NatureShare: Cassytha melantha.