Peppermint is apparently a hybrid between Spearmint (Mentha spicata) and Watermint (Mentha aquatica). If nothing else, the scent and flavor of the leaves are enough to identify the plant. It shows a strong preference for damp locations, although it will grow almost anywhere you plant it. It seldom produces viable seed, but it nevertheless makes a nuisance of itself in some parts of the country. Around here it is only an occasional tasty volunteer. This colony was growing in a wet depression beside a tributary of Wexford Run, where it was blooming in early September.

Linnaeus described this plant as a species, M. piperita; the × in Mentha × piperita denotes that the universal judgment of modern botanists identifies it as a hybrid. Gray’s description:

MÉNTHA [Tourn.] L. MINT. Calyx Ьеll-shaped or tubular, the 5 teeth equal or nearly so. Corolla with a short included tube, the upper lobe slightly broader, entire or notched. Stamens 4, equal, erect, distant. — Odorous perennial herbs; the small flowers mostly in close clusters, forming axillary capitate whorls, sometimes approximated in interrupted spikes, produced in summer, of two sorts as to the fertility of the stamens in most species. Corolla pale purple or whitish. Species mostly adventive or naturalized from Europe, with many hybrids. (Minthe of Theophrastus, from a Nymph of that name, fabled to have been changed Into Mint by Proserpine.)

M. piperìta L. (PEPPERMINT.) Glabrous, very pungent-tasted; leaves ovate-oblong to oblong-lanceolate, acute, sharply serrate; spikes becoming loose; calyx glabrous below, the teeth hirsute. — Along brooks, frequent. (Nat. from Eu.)

A strong and flavorful mint, similar in scent and taste to Spearmint (M. spicata). The flower spikes are the most distinguishing feature: flowers bloom in dense cylindrical spikes, like green fingers, rather than the looser interrupted spikes of Spearmint. Apple Mint grows in sunny waste places; this patch was growing on a weedy bank next to a softball field in Beechview, where it was blooming in the middle of August.

Gray lists this species as Mentha rotundifolia:

MÉNTHA [Tourn.] L. Mint. Calyx Ьеll-shaped or tubular, the 5 teeth equal or nearly so. Corolla with a short included tube, the upper lobe slightly broader, entire or notched. Stamens 4, equal, erect, distant. — Odorous perennial herbs; the small flowers mostly in close clusters, forming axillary capitate whorls, sometimes approximated in interrupted spikes, produced in summer, of two sorts as to the fertility of the stamens in most species. Corolla pale purple or whitish. Species mostly adventive or naturalized from Europe, with many hybrids. (Minthe of Theophrastus, from a Nymph of that name, fabled to have been changed Into Mint by Proserpine.)

Spikes narrow and leafless, densely crowded; leaves sessile or nearly so.

Spikes not canescent.

M. rotundifòlia (L.) Huds. Soft-hairy or downy; leaves broadly elliptical to round-ovate and somewhat heart-shaped, rugose, coarsely crenate-toothed; spikes slender. — At a few stations, Me. to O., Fla., and Tex. (Nat. from Eu.)

Also known as False Dragonhead, referring to its resemblance to a snapdragon. The name “Obedient Plant” describes a property that fascinates children, and any adults who are not too jaded to admit to being fascinated. If you push one of the individual flowers to the left or right, it will stay in that position. You can arrange all the flowers artistically on the stem, and they will stay right where you put them. You might almost think the plant had been specially bred by lazy florists. This plant was part of a large patch blooming in late July in a wet depression in Schenley Park.

Gray describes the genus and the species:

PHYSOSTEGIA Benth. FALSE DRAGON HEAD. Calyx obscurely 10-nerved, short-tubular or bell-shaped, more or less enlarged and slightly inflated in fruit. Corolla funnel-form, with a much inflated throat, 2-lipped; upper lip erect, nearly entire; the lower 3-parted, spreading, small, its middle lobe larger, broad and rounded, notched. — Smooth perennials, with upright wand-like stems, and sessile lanceolate or oblong mostly serrate leaves. Flowers large and showy, rose or flesh-color variegated with purple, opposite, crowded in simple or panicled terminal leafless spikes. (Name from physa, a bladder, and stege, a covering, in allusion to the calyx, which is at length somewhat inflated.)

• Stem conspicuously leafy up to the inflorescence.

P. virginiàna (L.) Benth. Stem 0.6-1.3 m. high, terminated by asimple virgate spike or several panicled spikes ; leaves thickish, mostly sharply serrate; calyx tubular-campanulate, its teeth half the length of the tube, acuminate, at length acerosetipped; corolla 1.8-2.3 cm. long. — Wet grounds, from w. Que. westw. and southw.; frequently escaped from cultivation in e. N. E. June-Sept.

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In her Guide to the Wild Flowers (1899), Alice Lounsberry gives us this description:

Flowers: growing closely in a dense spike on axillary flower-stalks. Calyx ; bell-shaped, of five-toothed sepals. Corolla: funnel-form; inflated; two-lipped, the upper lip arched and broad; the lower one of three spreading lobes, the centre lobe pale and dotted with a deep colour. Stamens: four; in pairs. Pistil: one; style two-lobed. Leaves: opposite; lanceolate; serrated. Stem: square; one to four feet high; slightly branched.

When a little fish comes to the surface of the water and opens his mouth his expression is not unlike that of these flowers. They have, however, none of the darting, evasive tendencies of the fish. The flower is most docile. Strangely enough, it appears to be without any elasticity, and will remain in exactly the position in which it is placed for an indefinite time. From this characteristic the plant quite carries off the palm of obedience among the flowers.

You could look at spearmint as an invasive wed, but it gives us so much in return for the space it takes that it’s a hard weed to resent. Spearmint spreads mainly by runners, forming large, dense patches. Its scent and flavor are recognizable at once. It blooms with pleasant spikes of little white flowers that were attracting little green flies when this picture was taken. This plant was part of a large patch blooming in late July in Beechview.

Flowers. In terminal spikes;  white with pink lines especially on upper lip; in whorls of a dozen or more; stamens twice the length of the corolla.

Leaves. Sessile; ovate-lanceolate, deeply veined, looking wrinkled; toothed, about 2 and a half or 3 times as long as broad.

Stems. Square, about 3 feet tall, wiry, often branching near the flower spike. Long underground or at-surface stems from which upright stems rise at rooting joints.

The whole plant is, of course, strongly aromatic, and its aroma and flavor are its most identifiable characteristics.

Gray describes the genus and the species:

MENTHA [Tourn.] L. MINT. Calyx Ьеll-shaped or tubular, the 5 teeth equal or nearly so. Corolla with a short included tube, the upper lobe slightly broader, entire or notched. Stamens 4, equal, erect, distant. — Odorous perennial herbs ; the small flowers mostly in close clusters, forming axillary capitate whorls, sometimes approximated in interrupted spikes, produced in summer, of two sorts as to the fertility of the stamens in most species. Corolla pale purple or whitish. Species mostly adventive or naturalized from Europe, with many hybrids. (Minthe of Theophrastus, from a Nymph of that name, fabled to have been changed Into Mint by Proserpine.)

Spikes narrow and leafless, densely crowded; leaves sessile or nearly so.

Spikes not canescent.

M. spicata L. (SPEARMINT.) Nearly smooth; leaves oblong-or ovate-lanceolate, unequally serrate, sometimes short-petioled; bracts linear-lanceolate and subulate, conspicuous. (M. viridis L.) — Wet places, common. (Nat. from Eu.)

This is probably your cat’s favorite herb, but it seems to have almost the same intensely euphoric effect on little white butterflies, to judge by the swirling masses of them that were visiting this plant. It was blooming in late July at the edge of an overgrown gravel drive in Scott Township. A tisane can be made from the leaves, but your cat will probably drink it before you get a chance at it.

Nepeta cataria is the only species commonly found in the wild around here. In Gray, the genus Glechoma is also included in Nepeta.

NÉPETA L. CAT MINT. Calyx tubular, often incurved. Corolla dilated in the throat; the upper lip erect, rather concave, notched or 2-cleft ; the lower 3-cleft, the middle lobe largest, either 2-lobed or entire. —Perennial herbs. (The Latin name, thought to be derived from Nepete, an Etruscan city.)

§ 1. CATARIA [Tourn.] Reiohenb. Cymose clusters rather dense and many-flowered, forming interrupted spikes or racemes; upper floral leaves small and bract-like.

N. catària L. (catnip.) Downy, erect, branched; leaves heart-shaped, oblong, deeply crenate, whitish-downy underneath; corolla whitish, dotted with purple. — Near dwellings; a common weed. July-Sept. (Nat. from Eu.)

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In his Field Book of American Wild Flowers, F. Schuyler Mathews becomes uncharacteristically personal in describing this plant:

Nepeta cataria. An exceedingly common weed to which many of the animals of the tribe Felis are greatly attached. A favorite Manx cat of mine would walk a mile every other day or so, from my Campton studio to a spot where it grew in plenty, notwithstanding the way was through the woods and over a hill of no small difficulty! The stem is densely downy as well as the deeply round-toothed leaves, and both are sage green in color. The pale lilac or lilac-white and spotted flowers are also downy, and gathered in small terminal clusters, which are rarely 4 inches long. Leaves strongly aromatic. 2-3 feet high. Common everywhere. Naturalized from Europe.

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In Wild Flowers East of the Rockies (1910), Chester Albert Reed gives us a little more of the lore of Catnip:

CATNIP (Nepeta cataria) (EUROPEAN) is a very common mint, introduced from Europe, the aromatic foliage of which has a very peculiar attraction for all members of the feline race. It apparently has an intoxicating effect upon them; after eating the leaves they will roll about on them for a long time. It also formerly was used for making Catnip tea, a one-time remedy for most of the ills of childhood. The plant has a stout, square hollow stem from 2 to 3 feet tall and is downy, as are the sage green, toothed leaves. The lilac-white flowers are clustered on peduncles from the axils of the leaves. Catnip is common throughout our range.