This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
A vast genus abounding in tropical countries, and a few species reaching the warm temperate parts of North America. Trees, shrubs, or herbs with abruptly pinnate leaves and paniculate or racemose usually yellow showy flowers. Sepals imbricate. Petals 5. Stamens 5 to 10, unequal, some of them abortive. An old Greek name.
1. C. Marilandica. - An herbaceous glabrous perennial, 3 to 4 feet high. Leaflets 10 to 20, lanceolate-oblong, obtuse. Flowers in axillary racemes, yellow. A native of North America, where it is called Wild Senna.
There are some of the annual species which might be grown in the open air. C. nictitans and C. procumbens are hardy North American annuals.