Cytisus scoparius (Common Broom; syn. Sarothamnus scoparius) is a perennial, leguminous shrub native to western and central Europe from the Iberian Peninsula north to the British Isles and southern Scandinavia, and east to Poland and Romania, where it is found in sunny sites, usually on dry, sandy soils at low altitudes.

It typically grows to 1-3 m tall, rarely 4 m, with main stems up to 5 cm thick, rarely 10 cm. It has green shoots with small deciduous trifoliate leaves 5-15 mm long, and in spring and summer is covered in profuse golden yellow flowers 20-30 mm from top to bottom and 15-20 mm wide. Flowering occurs after 50-80 growing degree days. In late summer, its legumes (seed pods) mature black, 2-3 cm long, 8 mm broad and 2-3 mm thick; they burst open, often with an audible crack, spreading seed from the parent plant. It is the hardiest species of broom, tolerating temperatures down to about -25°C.

There are two subspecies:

• Cytisus scoparius subsp. scoparius. Throughout the species' range.
• Cytisus scoparius subsp. maritimus (Rouy) Heywood. Western Europe, on maritime cliffs. Differs in prostrate growth, not over 0.4 m tall, and downy young shoots.

In Britain and Ireland the standard name is Broom, but this name is also used generically for other related species (see broom), and the term Common Broom is sometimes used for clarification. In other English-speaking countries, the most prevalent common name is Scotch Broom ; English Broom is also occasionally used (see Scotch and England).

Cultivation and naturalization

It is widely cultivated as an ornamental plant, with several cultivars selected for variation in flower colour, including 'Moonlight' with deep yellow flowers, 'Andreanus' and 'Firefly' with dark orange-red flowers, and growth habit, including 'Pendula' with pendulous branchlets.

It has been introduced into several other continents outside its native range and is classified as a noxious invasive species in California and the Pacific Northwest in North America, Australia and New Zealand. It commonly grows in disturbed areas along utility and transportation right-of-ways. The prolific growth of this species after timber harvest inhibits reforestation by competing with seedling trees. It is estimated that in Oregon it is responsible for USD$47 million in lost timber production each year in that state. Some attempts have been made to develop biological controls in affected areas, using three broom-feeding insects, the psyllid Arytainilla spartiophylla, the beetle Bruchidius villosus, and the moth Leucoptera spartifoliella.

In New Zealand broom is estimated to cost farmers NZD$10 million and the forestry industry NZD$90 million. Biological control for broom has been investigated since the mid 1980s with a number of species being trialled. They include the broom twig miner (Leucoptera spartifoliella), the broom seed beetles (Bruchidius villosus) the broom gall mite (Aceria genistae) the sap-sucking broom psyllid (Arytainilla spartiophila) and recently the broom leaf beetle (Gonioctena olivacea) and the broom shoot moth (Agonopterix assimilella). However, these insects can also eat native plants as well.

Images

Royal connection

The surname of the House of Plantagenet, rulers of England in the Middle Ages, was derived from common broom, which was then known as "planta genista" in Latin.

References

External links

• Bioimages - numerous photos
• Growing native plants
• U.S. invasive species info page
• Canada invasive species description