Unknown Plant

Unknown Plant

Observation - Unknown Plant - UK and Ireland. Description: I have been trying to find out what this plant is for months and it has just flowered (see photo) It has a square hairy branched stem, and has now grown to about 4 feet high in places, It has appeared on the edge of a field where the ground was cleared of

I have been trying to find out what this plant is for months and it has just flowered (see photo) It has a square hairy branched stem, and has now grown to about 4 feet high in places, It has appeared on the edge of a field where the ground was cleared of bramble and H balsam last year