The genus Colutea usually belongs to the Fabaceae family, although some literature classifies it as belonging to the Leguminosae family. Both families are the pea family and the Colutea flowers and seedpods typically resemble the pea plants. Some of these sweet-scented plants are medium-sized shrubs, while others are tree-like shrubs. Generally, they are native to southern Europe across the Himalayas. The plant was a medicinal plant in ancient Turkey and scientists continue to study its healing potential.
The bladder-senna, or C. arborescens, is one of the most popular Colutea plants for gardeners. It sometimes grows up to 15 feet (4.5 m) tall and wide, depending on the climate and cultivar, and has dull green leaves that measure up to 6 inches (about 15 cm) long. The leaves usually grow in five to six pairs of broad elliptical to ovate leaflets. The yellow flowers grow in racemes up to 5 inches (about 13 cm) long and each raceme contains between three to eight flowers. The 3 inch (about 8 cm) long seedpods change from green to a papery translucency as they mature.
In contrast to the tall bladder-senna, the bushy C. orientalis usually grows to a rounded 6 foot (about 2 m) height and width. The leaves are pinnate, meaning it has a central axis or stem that has parts branching from it, and range from bluish-green to gray-green. The flowers are coppery red with yellow markings and grow on racemes that may be up to 2.5 inches (about 5 cm) long. The individual leaves are obovate, meaning they are egg-shaped, tapering toward the tip.
The C. media is a hybrid of the two species mentioned above. It grows to 10 feet (3 m) tall. The blue-green to gray-green leaves are often 6 inches (15 cm) long and grow in three to six pairs of elliptical leaflets. The flowers are orange-brown, sometimes described as copper colored, and sometimes have a yellow center. The seedpods often are 3 inches (8 cm) long and change from a green-brown to translucent as they mature.
In Turkey, ancient healers used the leaves and fruits of the plant to treat inflammatory wounds. Some herbalists use the leaves for their laxative properties. In modern times, scientists and pharmaceutical companies are studying it for possible medicinal potential. A person should use caution when trying tonics made with Colutea plants because the seeds may cause stomach upset.
Colutea shrubs generally are very good garden plants. They often tolerate poor, dry soil where many shrubs do not thrive. Typically, they are excellent city plants, especially in coastal cities, because they tolerate pollution and salty air. Generally, they grow in full sun. In their native lands, such as eastern Africa, Iran, and Afghanistan, they usually grow in dry woodlands and thickets.