Parasitic plants

Root parasite Euphrasia revoluta. Photo: Mike Thorsen.

Parasitic plants belong to about 19 families of flowering plants. The Viscaceous and Loranthaceous mistletoes comprise approximately three-quarters of all parasitic species. Several other families of parasitic flowering plants are also well known, especially the broomrapes (Orobanchaceae) and dodders (Cuscutaceae).

Parasitic plants have a modified root called the haustorium which penetrates the host plant and connects to the host's xylem and/or phloem.

Ileostylus micranthus attached to a Coprosma proquinqua. Photo: Jesse Bythell

There are a number of terms associated with parasitism: 

  • Root parasite: attaches to the host root.
  • Holoparasite: completely parasitic on other plants and has virtually no chlorophyll.
  • Hemi-parasite: parasitic but also photosynthesises itself. Obtains water and mineral nutrients and may obtain part of its organic nutrients from the host.
  • Obligate parasites: cannot complete its life cycle without a host.
  • Facultative parasite: can complete its life cycle independent of a host.
  • Stem parasite: attaches to the host stem.

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This page last updated on 29 May 2014