JerryAnyone on here live where purple locust trees are native? Ohio maybe? I have bought 2 royal robe grafted trees from Stark Bros. but each time the graft dies after 1 year. I would like to try seed. The rootstock looks like black locust. Plenty of those around here.
The parent cross is Robinia hispida and Robinia pseudoacacia they graft it on Pseudoacacia root stock. Thats why sometimes you see them sucker and flower white.
If I recall hispid a forms a thicket or can but have a pinkish lavender flower.
another option is to search for another source.
Robinia Purple Robe is prone to breakage from wind and snow but I would think the grafts would not fail so easy.
I work for a large California Nursery and we buy in Bareroot shifters for 15's and 24" and rarely have any graft issues.
maybe start with a larger tree or skip the barefoot and get a established plant in a container