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.)