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|Orobanche purpurea (yarrow broomrape)|
Broomrape or broom-rape (Orobanche) is a genus of over 200 species of parasitic herbaceous plants in the family Orobanchaceae, mostly native to the temperate Northern Hemisphere. Some species formerly included in this genus are now referred to the genus Conopholis. The broomrape plant is small, from 10–60 cm tall depending on species. It is best recognized by its yellow- to straw-coloured stems completely lacking chlorophyll, bearing yellow, white or blue, snapdragon-like flowers. The flower shoots are scaly, with a dense terminal spike of 10-20 flowers in most species, though single in O. uniflora. The leaves are merely triangular scales. The seeds are minute, tan-to-brown, and blacken with age. These plants generally flower from late winter to late spring. When they are not flowering, no part of these plants is visible above the surface of the soil.
As they have no chlorophyll, they are totally dependent on other plants for nutrients. Broomrape seeds remain dormant in the soil, often for many years, until stimulated to germinate by certain compounds produced by living plant roots. Broomrape seedlings put out a root-like growth, which attaches to the roots of nearby hosts. Once attached to a host, the broomrape robs its host of water and nutrients.
Some species are only able to parasitise a single plant species, such as ivy broomrape Orobanche hederae, which is restricted to parasitising ivy; these species are often named after the plant they parasitise. Others can infect several genera, such as the lesser broomrape O. minor, on Trifolium and other related Fabaceae.
Branched broomrape Orobanche ramosa, native to central and southwestern Europe but widely naturalised elsewhere, is considered a major threat to crops in some areas. Plants that are parasitized are tomato, eggplant, potato, cabbage, coleus, bell pepper, sunflower, celery, and beans. In heavily infested areas, branched broomrape can cause total crop failure.
Branched broomrape was found near Bowhill, South Australia in 1992, and some properties have been quarantined for more than a decade. The weed could become a national problem in Australia unless it can be contained.
The scientific name comes from Ancient Greek ὄροβος (orobos, “bitter vetch”) + ἄγχω (ankhō, “strangle”). The common English name comes from its originally being found and described on broom (Cytisus spp.) and it was realized what damage it does to them.
Naked broomrape (Orobanche uniflora)
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- Devonshire Association for the Advancement of Science, Literature and Art (1868). Report & transactions. p. 256.
- GRIN. "Species in GRIN for genus Orobanche". Taxonomy for Plants. National Germplasm Resources Laboratory, Beltsville, Maryland: USDA, ARS, National Genetic Resources Program. Retrieved October 30, 2009.
- "Plant Name Query Results for Orobanche". IPNI. Retrieved November 1, 2009.
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