The castor bean plant is a fast growing annual plant that can reach a total height of 6 to 15 feet tall. In frost-free areas they may live many years and become tree-like. Castor bean plants have large leaves measuring over 20 inches and look largely tropical. Castor bean seeds can be tricky to locate since the seeds of the plant contains a potent toxin call ricin. The plant can become invasive in areas which are frost-free and may be listed on the invasive species list.
Research types of castor bean plants. The Zanzibar castor bean plant grows up to 15 feet tall and has large green leaves. The red spire castor bean grows up to 10 feet in height, has reddish stems and bronze-green foliage. The Sanguineus castor bean plant grows 10 feet or higher, has red stems and blood red leaves. The Carmencita castor bean plant grows 6 to 10 feet high and has burgundy stems and foliage. Figure out your space allotment and pick a type of castor bean that will fit accordingly.
Visit your local garden center and see if it carries castor bean seeds. A lot of garden centers are carrying more tropical plants to cater to the ever-growing desire to have a tropical-looking garden. You're most likely to find common (green-leafed) types of castor bean plants at garden centers since they try to cater to popular demand. If you can purchase them locally, you will save on shipping.
Visit online nurseries, seed stores, or eBay. You will likely have no problem locating castor bean seeds online. A lot more people are beginning to order their exotic stuff online and rarer, but more striking types of plants (including castor beans) are available. Ordering online, though, will set you back a little extra money because you'll have to pay for shipping.
Sign up with a seed swapping group. (See Resources for a popular one that swaps castor bean seeds.) With seed swapping groups, you generally pay a small membership fee. You then send them your seeds and receive "credits." Use these "credits" to then "purchase" your castor bean seeds.