The Crotalaria genus is not exclusive to Australia and there are around 600 species worldwide. In Australia there are approximately 26 indigenous species though there seems to be some dispute as to whether all of these are endemic as some may be naturalised. Crotalaria are native to the tropical and sub-tropical areas of northern and inland Australia, especially Western Australia.

The Crotalaria genus belongs to the Papilionaceae family which includes other legumes such as peas and beans. The Australian species include annual and perennial plants and many are ephemeral annuals that grow quickly. Typically the flowers are yellow or lime green though there is at least one species, Crotalaria verrucosa (Blueflower Rattlepod) that bears bluish-purple flowers. The flowers of all the Crotalarias are followed by inflated pods. When they mature and dry, the seeds rattle inside, thus giving rise to the common name.

Some of the native Crotalaria species are poisonous to stock. Crotalaria crispata, C. eremea, C. aridicola and C. medicaginea are all potentially dangerous to grazing farm animals.

Not many of the Australian species have made it into cultivation but there are several that make very interesting garden plants. Crotalaria laburnifolia is commonly called Birdflower. It bears very large, dramatic yellow flowers. The unopened buds look like small birds clinging to the stems. This is a perennial plant with a slender habit and attractive leguminous foliage. It grows to around 2m tall. While it hails originally from inland riverine areas of north western WA, NT and North Qld, it will tolerate a range of climates. (For instance I have watched with interest the progress of several plants in a native garden in Melbourne over a period of 8 years and they invariably flower around March/April.) The flowers are very striking.

Another species that makes a handsome garden plant is Crotalaria cunninghamia. This slender shrub grows in inland areas and has felted grey foliage and spectacular lime green flowers that are followed by puffy, club-shaped pods. In the north, its common name is Parrot Pea. While it is comparatively short-lived, new plants can easily be propagated from seed.

As well as being very decorative, Crotalarias have a role to play in the life cycle of native insects such as the pretty speckled Crotalaria Moth and butterflies such as Long-tailed Pea-blues.

Illustrations from top to bottom:
1. The striking pea-flowers of Crotalaria laburnifolia.
2. The trifoliate leaves of Crotalaria laburnifolia.
3. The buds look like small birds attached to the stem by their beaks. 
4. The large inflated seed pods rattle when dry.