Mentha aquatica is similar to mentha arvensis, differing in the tubular rather than bell-shaped calyces, and for having the largest flower cluster at the top of the stem rather than lower down.
Main flower color:
All of the British Isles, except high elevation regions
Up to 60 cm
Damp woodland and meadows, and shallow water along the edges of lakes and ponds
The corolla is pale pink, around 4 mm long; narrowly funnel-shaped, opening to five lobes, slightly uneven along the margins, and hairy on the outer surface. Stamens are strongly exserted. Flowers form mainly as a rounded to slightly elongated terminal cluster, usually with one or two smaller whorls at the leaf nodes below
Opposite, ovate, hairy (especially underneath), lined by small, shallow teeth; up to 6 cm long and 4 cm across
July to October