Die Fen Nettle differs from the normal Stinging Nettle mainly by the fact, that it has no stinging hairs at its leaves and few at the stem. Moreover the plant becomes higher, has more narrow leaves, and a different number of chromosomes. Mainly it grows in damp woods.
There are botanists who don't accept this subspecies. Their opinion is that the different attributes don't occur together but in different combinations, and that these plants show the big variability of Urtica dioica.