I have grown Incarvillea in the past, but only I. delavayii seems to show up in the nurseries, and then only very rarely. (I may see only one plant every three years, or so.) I looked up the other species you mentioned, and they look nice. I will have to check out if they will grow in our climate, and debate with myself about going the mail order route.

I love rehmannia and they grow well here. It is one of those never-too-many plants that I encourage to grow everywhere throughout the yard. I made some new beds recently by removing some concrete, and went shopping for 5 1 gal. rehmannias to plant. But both nurseries were out. They are offered off and on throughout the year, so I will wait or move some starts.

and the rehmannia bloom for ages too. I haven't grown them from seed (and they are like gold-dust in nurseries over here too), but the incarvillea are easy to grow from seed (no need for stratifying or heat).