J&P supplies bare root roses on fortuniana rootstock. The Sunsprite roses I bought through GVR I'm pretty sure were on fortuniana rootstock; the roots looked different, the roses set leaves earlier that Sunsprite roses from Edmunds, and the color of the new foliage had little or no purple coloration. The tags on the Sunsprites from GVR said they came from J&P. FWIW.
In any case, thanks for the tips on soaking roses, Zuzu. It gives me the rare chance to celebrate the utility of being lazy.
