"They grow wild in Norway, at high(ish) altitudes and in boggy ground ( I think!). They often appear as "local delicacies" in restaurants there, and are quite expensive as I recall.
I'm guessing growing conditions in Italy are quite…"
"Glyphosate will see them off eventually, but may need several applications. Try strimming them down to ground level, and then spraying the newly emerged foliage a few weeks later - the young foliage will absorb the chemical more effectively. Give it…"