Parasitic plants require other plants to gather nutrients and water in order to thrive and survive. About 15 families of flowering plants make up parasitic plants with many of them falling into the mistletoe species. Parasitic plants attach themselves to the host plant via their vascular system, or tissues. The plants propagate when their seeds land on the host plant’s tissue; once the seed germinates, its root penetrates the host, allowing it to share the host plant’s food. While parasitic plants rarely cause the host plant to die, they do seriously affect its growth.
Also known as big leaf mistletoe, Christmas mistletoe (Phoradendron macrophyllum) remains best known for its green leaves and red berries used during the holidays. The perennial flowering plant parasitizes nearby trunks and branches of woody trees and shrubs including cottonwoods, willows, alders and sycamores. The plant uses specialized roots to invade the host plant and absorb nutrients. The plant spreads thanks to birds who eat the seeds and disperse them into other areas or on the branches of trees where the seeds germinate.
Thurber's pilostyles (Pilostyles thurberi) consists of a tiny stem parasite that produces a beautiful little flower. In the Colorado Desert of the southwestern United States, the barely noticeable parasitic plant lives on the stems of dyeweed, a short, sweet-smelling desert shrub. The plant becomes more obvious after its tiny reddish buds pop open into small dark red blossoms. The flowers stay on the plant up to a year. Once the flowers disappear, they leave small round scars or craters on the host plant, the only evidence that the parasitic plant grew there. Pilostyles grows in deserts in the United States, Costa Rica, Chile, Australia and Ethiopia, among others.
Western Australia Christmas Tree
One of the larger parasitic plants, the Western Australia Christmas tree (Nuytsia floribunda) grows in an area of western Australia from the Murchison River to the west end of the Great Australian Bight. The tree prefers sandy soil in open forests where its roots can attach themselves to other plants. Sometimes the plant uses other trees up to 400 feet away as a host. The tree grows up to 25 feet in height with a profusion of golden-yellow flowers appearing in the summer. Propagation of the plants remains difficult since plants grown from seed or cuttings rarely survive for more than one to two years.
Also known as smartweed dodder, the knotweed dodder (Cuscuta polygonorum) grows as a stem parasite. The native parasitic plant grows in swampy and forest lowland areas in the Midwestern United States. Knotweed dodder uses plants such as buttonbush and jewelweed as host plants. The annual vine features four-petalled white flowers. The plant remains on the plant species of special concerns list.