Cassia, also known as Wild Senna grows from Pennsylvania down to Florida and west to Texas. It is a woody herb, about 6 feet tall with alternate leaves and leaflets. The flowers are bright yellow and it blooms here in late summer. The leaves were listed for medicinal purposes for many years in the United States Pharmacopoeia. Youngken says that the leaves contain the same principle found in the East Indian senns sold in drugstores, but in lesser amounts.
Many people have heard of senna as a leading purgative, and for such a use the wild American form seems to be equally valuable. The recommended dose was a teaspoonful steeped in boiling water for half an hour, taken a little at a time during the day, or a half-cupful at night. Caution is suggested, however, since very small quantities can cause severe diarrhea. Maybe this is another case of the cure being worse than what you're taking it for. I believe that senna was/is an active ingredient in some over the counter laxatives. I think I'll avoid it and just enjoy the flowers.
The plant was used as a cathartic by the Native Americans, who also made poultices from the moist, bruised roots for sores, and a decoction from the roots for fevers.
There are few references to senna in the early European herbals because the Cassia of the drug trade came largely from Arabia, India and similar climatic and cultural centers which, in the centuries of herbal compilation, had little communication with the West. Similarly, Europeans knew little of Native American medicine at that time.
This is a plant for a sunny, even a bit dry spot. It will grow in shade, but will probably not flower well there. It is a reliably hardy perennial and we have had it in the garden for many years. It also makes a pretty good cut flower.