This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The habitat of this plant is river-sides, marshes, moist places. The habit is erect. The plant is usually softly hairy. The stems are 4-angled. The leaves are ovate to oblong or heart-shaped, the upper ones bract-like, not so long as the flowers, stalked, coarsely toothed, hairy both sides, opposite. The flowers are lilac, in axillary and terminal, dense, capitate spikes, which are ovoid, round, oblong, continuous or interrupted below. The ultimate flower-stalks and flowers are hairy. The bracts and bracteoles are awl-like to lance-shaped. The calyx-teeth are slender. The calyx is glandular, smooth, tubular. The plant is 1-5 ft. high, flowering in August and September, and is a herbaceous perennial.
Mentha alopecuroides, Hull = M. velutina, Bab. - The habitat of this plant is waste places. There are subterranean stolons. The leaves are very broad, more or less heart-shaped below, coarsely toothed, rather wrinkled above, very hairy below. The flowers are pink, in conical to cylindrical, short, stout spikes, with lance-shaped bracts, not so long as the flowers. The calyx-teeth are as long as the tube. The corolla is hairy. The plant is 2-3 ft. in height, and flowers in August and September. It is a herbaceous perennial.
M. aqua-tica X spicata). - The habitat of this plant is damp places. The plant has the mint habit. There are underground stolons. The whole plant is devoid of hairs, and is more slender and smaller than Spearmint. The leaves are stalked, hairless, or hairy on the veins below, ovate to lance-shaped, oblong, acute, or blunt below, coarsely toothed, the upper leaves not so large. The flowers are lilac, in cylindric spikes, interrupted below, with close whorls, loose, short and blunt. The calyx is glandular, tubular, often red, smooth below, with awl-like, lance-shaped teeth. The plant has a purplish tint, and smells of peppermint. The plant is 1-2 ft. in height, flowering in August and September, and is a herbaceous perennial.
The habitat of this plant is wet places, waste places, marshes. The habit is as in Watermint. The plant is green. The leaves are nearly stalkless, hairy both sides, elliptical, ovate to lance-shaped, oblong, acutely coarsely toothed, the upper leaves smaller, longer than the flowers. The flowers are lilac, in an indeterminate inflorescence, with flowers in axillary, distant whorls, none at the top. The bracteoles are not so long as the flowers, long-pointed. The calyx-teeth are triangular, lance-shaped, not so long as the tube, acute, the calyx tubular or bell-shaped. The throat of the calyx is naked. The ultimate flower-stalks, calyx, and corolla are hairy. The plant is 1-3 ft. in height, flowering between July and September, and is a herbaceous perennial.
The habitat of this plant is watery places. The plant has been regarded as a variety or sub-species of the last, or as one parent if that be considered a hybrid. The stem and veins of the leaves are purple or red (hence rubra). The leaves are smooth or have a few distant hairs, and are stalked. The flowers arc lilac. The ultimate flower-stalks, lower part of the calyx, and corolla are smooth, the calyx-teeth hairy. The plant is 2-5 ft. in height, and is in bloom between July and October, the plant being a herbaceous perennial.
This plant, found in Wilts, is regarded as a variety of M. gentilis, L., or as a form of M. rubra, Huds. It is more slender, with the leaves more or less devoid of stalks, and green. The stem is hairy below. The leaves are oblong to lance - shaped, smooth or with a few hairs, the flowers in separate whorls, the lower bracts short - stalked, 5-6 times as long as the distant whorls, smaller and narrower than the leaves. The bracteoles are equal to or exceed the flowers. The calyx is fringed with hairs. The ultimate flower-stalks and corolla are smooth.
The habitat of this plant is river-banks, moist places, fields. The habit is erect. The stem is 4-angled, hollow, stout, with fine, turned-back hairs, less coarse than in the common Woundwort. The stem-leaves are opposite, shortly-stalked or stalkless, ovate, oblong to lance-shaped, narrow, linear, more or less heart-shaped below, scalloped to coarsely toothed. The lower leaves are short-stalked, the upper stalkless. The flowers are dull-purple, in whorls of 8-10, with lance-shaped, acute calyx-teeth, which are spinous, and minute bracts. The nutlets are shining, with small dots. The plant is 1-3 ft. in height, flowering from July to September, and is a herbaceous perennial.
This hybrid (between S. sylvatica and S. paluslris) has been found in 64 vice-counties from the Shetlands to W. Cornwall, and in Ireland (17), and the Channel Islands. It is not uncommon. The habitat is cultivated ground. The leaves are shortly-stalked, narrower than in the last, ovate to lance-shaped, heart-shaped below, coarsely toothed. The leaf-stalks may be half as long as the leaves.