Orobanche flava on Petasites hybridus (large leaves). Both species are introduced to Denmark.

Heide-Jørgensen H S, 2011. Parasitic plants. In: Simberloff, D and M Reymánek (eds.). Encyclopedia of biological invasions. Univ. Calif. Press, Berkeley and Los Angeles.

Parasitic flowering plants exploit other flowering plants for water and nutrients with the help of one or more haustoria. Part of the haustorium, the intrusive organ, penetrates host tissue to establish contact with the conductive tissue of the host. Introduced parasitic plants occur throughout the world and some are considered invasive. They often cause considerable economic damage when attacking monocultures in agriculture, orchards, and forestry, and much effort is done to avoid and control invasive, harmful parasitic plants.

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