I have tried to key out this plant in my Flower Key but cant find a satisfactory answer. Can anyone help.
I have found it in a woodland in South Wales, and believe it to be Lamiaceae because it has a square stem, toothed opposite leaves, and irregular flowers, with a 5- toothed calyx. This species stands about 1.5m at its tallest, in this location. The upper lip is dominant with a deep purple colour, the lateral lobes seem almost absent and the lower lip is very small and green, folding back against the corolla tube, almost like a shirt collar. The corolla tube is like a little cup and is filled with nectar. A single style protudes out of the corolla tube, but not beyond the top lip and there are four stamen in each flower.
Leaves are as large as 114mm and are hairless. Two edges of the square petiole join together just before the leaf starts, causing a kind of pleating to the leaf shape.