If you go to Home Depot, Lowes, etc. buy the grafted plants not the seedlings. At least if you are looking for multi-petaled desert roses. Almost no one grafts single petaled plants unless they are trying to put multiple colors on the same base. Seedlings of multi-petaled plants are as easy to grow as the singles but they don't come true to type. You may get single, double, triple, or just deformed flowers from the seedlings. No mass grower wants to waste resources growing seedlings except as bases for their grafts, and they typically use the same clone for their grafts and they are invariably single flowers but have good fat bases. So if you buy a grafted plant even not in flower the chances are very high that it will be multi-petaled. Someone thought it was special enough to warrant the extra work.