Choose a supplier of castor seeds. Suppliers can be found on the Internet at sites such as Amazon, Local Harvest, and SeedRack. Several varieties may be advertise; make sure the seeds you order are Ricinus communis.
Choose a seed quantity. Castor plants can take up significant vertical as well as horizontal space. Plan for a 12-foot-high shrub, six feet in diameter. Ten seeds, or 12 grams, should cost you about $4. Bulk orders can be filled by foreign suppliers, although import of castor seeds is prohibited in Australia.
Order the seeds using the website's order form and fill in your address. Choose method of delivery, and wait for the shipment.