Yes you can, Matilda, they come easily from seed. The easiest way is just to sprinkle a few seeds on the soil where you want them to grow, although I always start them off in pots. Be aware that they are unlikely to flower exactly as the parents. From the one seed pod you will get a variety of different forms some of which may be even nicer than the parent.

If they are Hybrids they won't come true.

If they are like the ones in my garden they come up all over the place without me doing a thing!!