Colutea arborescens is a perennial shrub native to the Mediterranean region. It often flourishes in temperate climates and usually grows well in any soil type. In many parts of the world it is often used as an ornamental shrub, and it is also used in landscaping for erosion control. These deciduous shrubs have earned nicknames such as bladder senna and bladder pod due to their bladder-shaped seed pods.
Found growing wild in areas such as southern Europe, North Africa, and the western Himalayas, Colutea arborescens are a favorite among gardeners in other regions because of their ability to survive in many conditions. These flowering shrubs do well in just about any well drained soil type, including acidic, neutral, and alkaline soils. Soils lacking in nutrients, however, seem to be the best choice for these types of plants, and unlike other plants, they generally thrive in it.
The leaves of the Colutea arborescens are bright green in the spring and summer, and color ranges anywhere from yellow to red in the fall. They are odd pinnate compound leaves, meaning that they are comprised of pairs of leaflets arranged on both sides of a rachia with an additional leaflet on the end. These are usually between three to six inches (7.6 to 15.2 centimeters) long, and there are typically between nine and thirteen leaflets that make up each leaf. Colutea arborescens generally grow to be around six to ten feet (1.8 to three meters) in height with a spread of about six feet (1.8 meters).
Flowers usually bloom on the Colutea arborescens during late spring and continue blooming until early fall. The bright yellow flowers often have small reddish markings on the petals. The pea-shaped flowers on these plants are typically about one inch (1.8 centimeters) and grow up to four inches (10.2 centimeters) long.
Bladder senna plants have earned their nickname due to the bladder shape of the seed pod they produce. Seed pods up to two inches (five centimeters) long can be found dangling from the branches of the bladder senna until late fall. The pods are usually light green to purplish in color during the summer and transform to a light translucent brown in the fall. Each seed pod contains several seeds that become exposed when the papery pods break open.
Colutea arborescens is a member of the fabaceae, or leguminosae, family. This large family is commonly referred to as the pea or bean family, and it considered to be one of the largest families of flowering plants. Other plants included in this family include peanuts, soybeans, and green beans.