Semiparasitic

Semiparasitic plants are plants that rely on a host plant for part of their nutrients but remain capable of photosynthesis. The term is often used interchangeably with hemiparasitic. Semiparasites form specialized structures called haustoria that connect to the host’s vascular system, typically the xylem, to take up water and minerals. Photosynthesis provides most of their carbon, so they are less dependent on the host for energy than holoparasites, though the host can substantially supplement their nutrition.

Most hemiparasites have a broad host range, while others are more selective. They are commonly found in forests and grasslands, often attaching to branches or roots of neighboring plants. The ecological role of semiparasites includes influencing plant community composition, nutrient cycling, and light availability. Their presence can affect the growth and distribution of neighboring species, with effects that vary by environmental conditions.

Examples include mistletoe (Viscum species, especially Viscum album in Europe), Rhinanthus (yellow-rattle), Castilleja (Indian paintbrush), and Pedicularis (lousewort). Distinction from holoparasites is that holoparasites lack chlorophyll and rely entirely on the host for carbon, whereas semiparasites occupy an intermediate position and may range in dependence depending on species and environment.

Human uses and study focus on semiparasites include weed management and ecosystem restoration, while mistletoes and related plants also hold cultural significance in various regions.