Epilobium fleischeri / Alpine Willowherb

Does anyone have experience growing this particular variety of willowherb? I'm concerned about the aggressiveness, based on my experience with E. angustifolium, which required a serious assault to remove last spring after it escaped the bucket.

Some sources say the fleischeri is "compact" and others say the rhizomes are no better behaved than those of the regular willowherb.

My soil is silty loam-- well drained, on the lean side. Cdn zone 6b.

I'd like to hear about your experience growing this.

Thanks.