I have been growing Cleomes from seed for years. Mostly because it is a great background plant, it is airy, drought tolerant and EASY to grow from seed. Once you successfully grow one plant you will have enough seed to share with the whole neighborhood next year.
The seed pods look like little beans. They pop open in your hand.
Allowing you to easily collect seeds for next year.
They will re-seed themselves and you have to look carefully when weeding your flower beds for cleome seedlings. These seedlings will need separating and moving around because they will be thick. The plants to be a little fussy when you move them, so move them when the plants are young, just a couple of inches high. (You will have enough seedlings that it will be ok if some don't make it.)