Inspect your castor bean plant for seed pods. Seed pods form during the growing season; they become much larger and more visible in late fall. If you have trouble locating pods, check deep within the plant, shifting aside the large leaves for better visibility.
Chart the weather. The best time to harvest castor bean seeds is right before killing frost. Try not to wait until after the killing frost, as it can cause the seed pods to burst and the seeds fall to the ground. Check your weather daily and be prepared.
Check the growth of the seed pods. As the pods ripen, they turn dark brown and feel dry and leathery to the touch. If you notice ripe seed pods, go ahead and harvest them rather then waiting to harvest all the pods at one time.
Harvest the castor bean seeds. Put on a pair of gloves, as contact with the seeds and pods can cause an allergic reaction in some people. Pick the seed pods directly from the tree. Place them into a container for storage.
Remove the seeds from the pods. While wearing gloves, gently break open the seed pods and rub your finger across the seeds. They will come loose from the pod and fall out into your hand. Castor bean seeds are the size of beans and have a distinctive mottling pattern.
Plant the seeds, or place them in a cool dark place for storage until you are ready to use them. Make sure children and animals will not have access to the storage place, as these seeds are toxic.
Clean up. If you used disposable gloves, throw them away. Wash other types of gloves and the clothing you wore during harvesting. Wash your hands and arms up to your elbows thoroughly.