I have rooted these in the past. Don't have to now as they increase fast enough not to be necessary any longer. Brian Whyer, Buckinghamshire, England, zone ~8 Well, I figured out what was happening with the black “wire”, but I figured it out too late: the black “wire” was in fact the sprout of one of the Chilean Tropaeolum. Because these plants branch freely, no permanent damage was done. The part of the stem I did not break off is perhaps eight inches long and already had started to branch.