On the other side of the continent from Fred in Cambridge, Mass, I too have growing patches of stoloniferous T. clusiana and T. c. chrysantha, both of which I enjoy very much, even when clumps insist on spreading out of beds in to turf areas. I have yet to see any sign of this behavior in T. sylvestris, however, much as I would like to have this one be stoloniferous. Kathleen Kathleen Sayce PNW Coast, WHZ 8, dryish cool summers & mild wet winters