Select the cleome plants that produce the most attractive blooms and grow the healthiest for seed saving. Monitor these plants for pod formation after their flowers begin to wilt. Cleome seed pods resemble bean pods and can measure 3 inches or more in length.
Hold a bowl beneath the seed pods after they swell and begin to dry. Squeeze the pod gently, starting at the top and pulling downward. Pods with ripe seeds easily split open, and the seeds will fall into the bowl. If a pod doesn't split, continue to try it daily until it ripens enough to spill its seed.
Spread the seeds out on a tray, and remove any stems and other unwanted material. Place the tray in a dry, warm place and allow the seeds to dry for one week. Stir the seeds daily so all sides dry evenly.
Label an envelope with the cleome variety and harvest date. Place the dried seeds in the envelope and seal it closed.
Store the envelope in an airtight jar or container. Keep the jar in a cool, dark place. Plant the seeds within one year of harvest to ensure the best germination rates.