This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Like numerous other aquatic types, Water Mint finds a place in the ancient floras preserved to us. It is represented in Preglacial beds at Pakefield, Suffolk; Interglacial and Roman beds at Silchester. The present distribution of the plant is Europe, N. Africa, N. and W. Asia, and it has been introduced into North America. This plant is universal in distribution in Britain, growing in every county in Great Britain as far north as the Orkneys, and up to a height of 1500 ft., for instance, in Yorks. It is a native also of Ireland and the Channel Islands.
Water Mint is a hygrophyte, luxuriating in the moisture of riversides, wet places by ditches, pools, and ponds, around the margins of which it forms quite a fringe in many places. Wherever a spring issues from a hill-side, one will also find it. It is a regular component of marsh and bog floras.
The stem is erect, stoloniferous with creeping shoots, many growing in a bed in association, square, roughly hairy, and leafy. The leaves are egg-shaped, stalked, coarsely toothed, roughly hairy, heart-shaped at the base. The uppermost leaves answer as bracts, and are less than the flowers.
The flowers are in a globular head, lilac, in whorls or forming a terminal head. The teeth of the calyx equal the tube, and are triangular. The calyx is regular or 2-lipped, glandular and hairy both sides. The flower-stalks have bent-back hairs. The whole plant has a strong scent. The corolla is nearly regular. The erect stamens are equal in size.
Water Mint is 1 1/2 ft. high. Flowers can be found between July and September. The plant is a deciduous, herbaceous perennial, propagated by division.
The small-flowered plants are female and not so common as the hermaphrodite. The anthers mature first, before the stigma. In the latter the tube is 4-5 mm. long, and 2 mm. wide at the mouth, otherwise the flower resembles M. arvensis. The corolla forms a bell. Honey is secreted in the ovary, which is enlarged. Honey is not so easily reached as in M. arvensis, but insect visits are more numerous because the plant is taller and the heads are larger and denser. It is visited by Halictus, Ichneumons, Empis, Ascia, Eristalis, Syritta, Helophilus, Syrphus, Melanostoma, Onesia, Sarcophaga, Musca, Chrysops.
Photo. G. B. Dixon - Water Mint (Mentha Aquatica, L.)
The nutlets are adapted to fall when ripe around the parent plant, or to be eaten by birds and travel some distance, being thus dispersed by the plant itself or by animals.
This fragrant plant is peat-loving, growing in wet, moist, peaty soil, or pelophilous, growing on clay soil.
A fungus, Puccinia menthae, Mint Rust, attacks the leaves. Five beetles, Meligethes viduatus, M. lugubris, M. obscurus, Chrysomela menthastri, C. polita; two moths, Pyrausta purpura/is (Crimson and Gold Moth), No/a a/bu/alis; a Heteropterous insect, Zicrona cceru/ea; and Eupteryx vittatus, a Homopterous insect, feed on it.
Mentha, Theophrastus, is from the Greek mintha or minthe; Mintha, a nymph, being transformed into this plant by Proserpine. The second name refers to the aquatic habitat. It is called Bishop's Weed, Bishop's Wort, Fish Mint, Baulme Mint. It smells strongly of peppermint, and an oil is expressed from this and other species for the manufacture of it.
Essential Specific Characters:246. Mentha aquatica, L. - Stem erect, with subterranean stoles, hirsute, leaves ovate, serrate, the upper ones less than the flowers, flowers lilac, axillary, and terminal, subglobose.