5 Awesome Parasitic Plants

Rafflesia arnoldii, the world’s largest individual flower, is kind of nasty. Found in the forests of Malaysia and Indonesia, its giant red-brown blossom is nearly 1 meter (3.3 feet) in diameter and weighs up to 11 kg (24 pounds). It smells like rotting flesh to attract carrion-feeding flies as pollinators and its sticky fruit is spread by rodents. If you’ve ever seen a picture of this “corpse flower,” you may have noticed its lack of leaves. This delightful organism is actually an obligate parasite and cannot photosynthesize on its own. In fact, 100% of its unpleasantness is fueled with nutrients it steals from the roots of neighboring Tetrastigma vines! Rafflesia makes parasitism pay off in a big smelly way.

On the opposite end of the size spectrum is the minute Pilostyles thurberi, or Thurber’s stemsucker. Native to the deserts of southwestern North America, P. thurberi is an obligate parasite on the stems of shrubs in the pea family (Fabaceae). Measuring only about 6 mm (0.25 inch) long, the tiny plant lives entirely within the stem tissues of its hosts and lacks roots, leaves, or chlorophyll. Its presence is only made known when it breaks through the bark of its host to flower. Each individual plant produces only male or female flowers and scientists are still unsure what exactly pollinates these teeny-tiny flowers or how populations coordinate their flowering.

Dodder (Cuscuta sp.) is a fairly well known group of parasitic plants that form iconic masses of yellow, leafless vines over their hosts. Dodder plants are aggressive and use root-like organs called haustoria to penetrate the stems of their hosts and siphon off their water and nutrients, often to the point of host-death. Given that dodder species have little to no chlorophyll with which to make their own nutrients, it is crucial for young seedlings to find a host before they run out of the energy supplied by their seeds (usually about 5-10 days). Studies have shown that these seedlings can use airborne volatile organic compounds to locate their host plants, almost like a plant-y sense of smell! Cuscuta seedlings can even detect which of their neighboring plants are more suitable hosts and will actively grow towards them. Once a young plant successfully reaches a host, its embryonic root rots away and it becomes wholly dependent on its parasitism. The fact that this plant can sense its hosts makes it a candidate for a creepy plant-horror film and earns it a place amongst its esteemed parasitic brethren.

Not to be confused with their Christmas-y namesake (which, incidentally, is also a parasite), dwarf mistletoe (Arceuthobium) species are found throughout the world and primarily parasitize conifer trees. Like dodder, dwarf mistletoes employ haustoria to exploit their hosts’ vascular tissues and do little to no photosynthesis of their own. While many parasitic plants spread to new hosts with the help of animals or the wind, dwarf mistletoe spreads from treetop to treetop using high-velocity projectile seeds! Yes, this plant actually explodes bullet-shaped seeds onto new hosts. Dwarf mistletoe fruits each house a single seed covered in a sticky substance. As the fruit matures, pressure builds up inside and causes the thick skin to rupture, shooting the seed away from the plant at speeds of up to 90 km/hr (56 mph)! The sticky covering helps the seed attach to the surface on which it landed, ideally the branch of a nearby conifer. Ballistic parasitic embryos. Enough said.

A tall and beautiful flowering tree, the Australian Christmas tree (Nuytsia floribunda) is an elegant parasitic plant. Native to dry regions in southwest Australia, N. floribunda towers over the other plants in the landscape and flowers when many other species are dormant. Equipped with green leaves, the plant is able to photosynthesize and provide its own nutrition, but acts as facultative parasite and steals water from its neighbors as necessary (which enables both its size and dry-season flowering). In fact, the tree maintains an extensive network of parasitic root connections with numerous other plants to exploit their various water supplies. Incredibly, the plant establishes these connections by severing the hosts’ xylem vessels with haustoria equipped with a guillotine-like structure! This mini-guillotine is so strong that it has mistakenly chopped through numerous underground power and fiber optic cables. Any plant with a guillotine gets brownie points in my book.