|Species in this genus|
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- Cultivation: Invastive, Naturalizing, Low-Maintenance, Easy-To-Grow
- Light: Sun
- Soil: Poor, Loam, Clay, Sand, Rock
- pH: 4, 5, 6, 7, 8
- Moisture: Wet, Medium, Dry, Well-Drained
- Form: Shrub
- Habit: Evergreen
- Flower: Large, Yellow
- Fruit/Seed: Medium, Fruit.Nut, Green
- Foliage: Leaves, Needles, Green
- Uses: Ornamental
Genista is a genus of legumes which includes many species of the plants known as Broom. So called because their twiggy almost leafless branches were traditionally used to make sweeping brooms in native European cultures.
Many of these brooms are notorious as Noxious weeds and some are used as very hardy landscape plants with masses of flowers.
Brooms are a group of evergreen, semi-evergreen, and deciduous shrubs in the subfamily Faboideae of the legume family Fabaceae, mainly in the three genera Chamaecytisus, Cytisus and Genista, but also in five other small genera (see box, right). All genera in this group are from the tribe Genisteae. These genera are all closely related and share similar characteristics of dense, slender green stems and very small leaves, which are adaptations to dry growing conditions. Most of the species have yellow flowers, but a few have white, orange, red, pink or purple flowers.
Two other close relatives are Ulex (gorse) and Laburnum (laburnum), but these differ more strongly in appearance from the brooms. Some botanists include Podocytisus caramanicus in the genus Laburnum.
Species of broom
The most widely familiar is common broom (Cytisus scoparius, syn. Sarothamnus scoparius), a native of northern Europe where it is found in sunny sites, usually on dry, sandy soils. Like most brooms, it has apparently leafless stems that in spring and summer are covered in profuse golden-yellow flowers. In late summer, its peapod-like seed capsules burst open, often with an audible pop, spreading seed from the parent plant. It makes a shrub about 1–3m tall, rarely to 4 m. It is also the hardiest broom, tolerating temperatures down to about -25°C.
The largest species of broom is Mount Etna broom (Genista aetnensis), which can make a small tree to 10 m tall; by contrast, some other species, e.g. dyer's broom Genista tinctoria, are low sub-shrubs, barely woody at all.
All the brooms and their relatives (including Laburnum and Ulex) are natives of Europe, north Africa and southwest Asia, with the greatest diversity in the Mediterranean region. Many brooms (though not all) are fire-climax species, adapted to regular stand-replacing fires which kill the above-ground parts of the plants, but create conditions for regrowth from the roots and also for germination of stored seeds in the soil.