PlantaeDB Logo
Login Sign-up

Genus Cytisus in Subfamily Papilionoideae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

Do you wish to read more about plant taxonomy? Click here!

Genus Description

Suggest a correction!

The genus Cytisus (Desf.) belongs to Fabaceae, subfamily Faboideae, tribe Genisteae, a group of Eurasian and North African “broom” shrubs characterized by reduced leaves and inconspicuous stipules. POWO (2024) lists about forty-eight accepted species, whereas WFO (2024) lists thirty-six, and GBIF (2024) treats roughly seventy, reflecting differing taxonomic treatments. The type is Cytisus scoparius (L.) Link (known as common broom). Plants are typically woody shrubs with strongly ridged green stems; leaves are trifoliolate and often small, with an appressed indumentum, and stipules are absent or minute. Flowers are solitary or in short axillary racemes; the calyx is tubular and two-lipped, the standard is reflexed and conspicuous, and the keel is rounded to slightly beaked. The ovary is superior and the fruit is a dehiscent legume; seeds have a fleshy aril.

Cytisus is most diverse in the Mediterranean basin and western Asia, with secondary centers in Macaronesia and Europe; several taxa are narrowly endemic to islands or mountain systems. Most species occupy open, dry, nutrient-poor habitats—maquis, garrigue, rocky slopes, and roadsides, often on acidic substrates; some reach high elevations in mountains. The genus contributes characteristic broom scrub elements to Mediterranean and temperate montane floras. Pollination is entomophilous, mainly by bees and butterflies, and dispersal is ballistic when dehiscent pods twist to fling seeds; several taxa naturalize outside their native ranges (e.g., C. scoparius in Australia, New Zealand, and western North America), a pattern reflected in GBIF occurrence data.

Intrinsic biology includes a well-supported base chromosome number x=23 (Luque & Ferrer, 1990) across surveyed species, consistent with many Genisteae. Growth forms vary from low cushions to tall shrubs, and many taxa exhibit a broom-like shoot architecture that promotes fire recovery through basal resprouting and seed germination after disturbance.

Recent work applies multiple circumscriptions. A broad, early-twenty-first century treatment (Klein, 2011) combined Cytisus and Chamaecytisus in a wider concept, whereas Euro+Med (2023) and regional Floras maintain a narrower Cytisus, excluding many former members as Chamaecytisus. Phylogenetic studies have repeatedly shown that Chamaecytisus is embedded within Genisteae, but relationships among Cytisus, Chamaecytisus, and Genista remain incompletely resolved and vary with sampling (Diez et al., 2009). Kew’s accepted-name list (POWO, 2024) aligns with the broader modern sense of Cytisus; WFO (2024) and national treatments follow the stricter delimitation, with C. scoparius as a widely accepted core member.

Human relevance is largely horticultural: several species, especially C. scoparius, are cultivated for their abundant yellow flowers and are used in reclamation and roadside plantings; introduced taxa can become invasive in some regions. The genus provides limited timber or minor craft material due to the size and habit of most shrubs.

Conservation attention concentrates on narrow endemics, but data are patchy and taxonomic instability obscures threat assessments. Baseline monitoring and a standardized phylogenomic framework are needed to clarify species limits and guide management.

Pick a Species to see its components: