Colutea is a genus of about 28 species of deciduous flowering shrubs belonging to the legume family Fabaceae (order Fabales). Members of the genus are native to the Old World, ranging across southern Europe, north Africa, and southwest Asia. Plants typically grow 2–5 metres tall and are sometimes known as bladder sennas, though they are not closely related to the true sennas (Senna).
The foliage is pinnate and light green to glaucous grey-green. In summer, plants bear pea-shaped flowers in yellow to orange hues, arranged in racemes. Their most distinctive feature is the inflated, bladder-like seed pods that follow flowering, ripening from pale green to shades of red and copper — an ornamental quality that has made the genus popular in gardens.
Colutea arborescens, the bladder senna, is the best-known species and has been cultivated in Britain since before 1568, initially thought to have been introduced for medicinal use. It tolerates poor, sandy, well-drained soils and has naturalised on railway embankments in the UK. The hybrid C. × media (C. arborescens × C. orientalis), which produces coppery flowers, is also in cultivation. Seeds are easily raised, making propagation straightforward.
Ecologically, Colutea species serve as larval food plants for the moth Coleophora colutella. The seeds of C. istria have historically been eaten by Bedouins in the Sinai and Negev during times of scarcity.
Etymology
The name Colutea derives from the ancient Greek koloutea, a name used by Dioscorides and other classical authors for a plant that is believed to correspond to this genus. The common name "bladder senna" refers to the inflated, bladder-like seed pods and the superficial resemblance of the foliage to true sennas, though the genera are not closely related.
Distribution
Colutea is native to southern Europe, north Africa, and southwest Asia. The genus extends from the Mediterranean basin — including Iberia, the Balkans, and north Africa — eastward through Turkey, the Caucasus, Iran, Afghanistan, and into Central Asia and China (C. delavayi). Colutea arborescens has become naturalised in parts of the United Kingdom, where it established itself on the sharp drainage of railway embankments.
Ecology
Colutea species function as larval host plants for Coleophora colutella, a moth in the family Coleophoridae (Lepidoptera). The inflated seed pods are dispersed partly by wind and partly by water, aided by the air-filled chambers. Plants tolerate dry, infertile, and rocky substrates, often colonising disturbed habitats such as road cuttings, embankments, and scrubland edges.
Cultivation
Colutea arborescens is the most widely cultivated species, grown chiefly for its ornamental bladder-like seed pods, which dry well and are used in floral arrangements. It thrives in poor, sandy, or gravelly soils with sharp drainage and performs less well in heavy or loamy ground. Propagation is straightforward from seed. The hybrid Colutea × media (C. arborescens × C. orientalis) is also cultivated and valued for its coppery-orange flowers.
Cultural Uses
The seeds of Colutea istria have been recorded as an emergency food among Bedouin communities of the Sinai and Negev deserts. Colutea arborescens was introduced to Britain, likely before 1568, reportedly for medicinal purposes, though it was eventually grown primarily as an ornamental.
