My experience with this species is that they tend to reseed where they are. Over time, the group will get larger. So my suggestion is let nature take its course. Or, harvest seeds from the ones that came up volunteer and put them where you want them. You can probably find seed companies that will sell you some seed online. There is one outfit down near Austin that farms wildflowers for seeds. Btw, bees love these. Caught a solitary bee on a cold morning sleeping in one of these.