Tall and handsome, Cleome hassleriana is also referred to as the spider flower or cat whiskers plant. Once these carefree tender annuals begin flowering in mid-summer, you can look forward to non-stop blooming right up until frost. Cleomes enthusiastically reseed themselves, but they're not fussy about where they deposit their offspring. If you’d like to choose future cat whiskers plant locations, harvest the generous bounty of seeds in late summer or early fall to plant next season.
Begin watching your blooming cleomes during the summer when seed pods begin to develop. The slim, bright green, elongated pods are about 2 inches in length and resemble a cat’s whiskers. They’ll turn a light tan color and feel dry to the touch when the seeds are mature enough to harvest.
Choose a warm, sunny day with no rain in the forecast. The pods should be picked when the weather is dry to reduce the chances of mildew forming on the seeds because of moisture collected from the air. Pluck a sample pod and roll it between your fingers. If mature, it will release hundreds of tiny black seeds into your hand.
Pick a few mature pods and take them indoors. Hold one over a bowl and roll it between your fingers to release the seeds into the bowl.
Dump the seeds into a clean glass jar. Cap it tightly. Label it with the seed variety and the date.
Store the cleome seeds in the refrigerator until you’re ready to plant next year.
Pull up spent plants at the end of the season. They’ll still have plenty of viable seed pods intact. Simply lay them wherever you’d like to have more sprout up next spring. Cleomes are happy to oblige by prolifically reseeding themselves year after year.