This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Perennial. Propagates by seeds and by rootstocks.
Time of bloom: June to September.
Seed-time: August to November.
Range: Nova Scotia to Ontario and Minnesota, southward to Florida and Tennessee.
Habitat: Prefers moist soil, but will grow anywhere.
Some thousands of acres in this country, particularly in the states of New York, Indiana, and Michigan, are very profitably given to the cultivation of this plant for the distillation of its oil, which is used in flavoring confectionery, in cordials and cosmetics, and also medicinally. But beyond the bounds of cultivation the plant is a troublesome weed. A bed of it in the herb garden is difficult of restriction within proper limits, as the long, underground suckers are continually thrusting up new plants where they are not wanted.
Fig. 252. - Peppermint (Mentha piperita). X 1/4.
Stems one to three feet tall, often tinged with reddish purple, smooth, square, erect and branching. Leaves dark green, lance-shaped, about half as wide as long, sharply toothed, smooth on both sides except that the veins beneath are slightly hairy, pointed at tip, rounded or narrowed at base to a short petiole. Flowers in terminal spikes, obtuse at tip, densely whorled or sometimes interrupted, purple, rather showy; calyx smooth at base but with nearly equal hairy teeth; corolla with upper lip entire and lower lip three-lobed; the four stamens, equal, erect and included; style two-cleft at summit. Nutlets four in each calyx, ovoid and smooth. (Fig. 252.)
A peppermint patch is about as difficult to clean out as is one of Quack Grass, for the rootstocks must all be removed from the soil or starved to death. In the one case, this means very diligent use of grubbing hoe and rake; in the other, such close and frequent cutting as to allow no green leaves to appear throughout the growing season.