Mentha x piperita.en.wikipedia.org. (Accessed 4/2014).

Mentha x piperita is a perennial herb, 0.6-1 m tall, strongly minty, sterile hybrid of M. aquatica and M. spicata, aggressively colonial from rhizomes and often also stolons, stems square, slender. 

Leaves opposite, stalk 0.4-1.5 cm long, blade 3-6 cm long, 1.5-3 cm wide, egg-shaped, tip pointed, sometimes blunt, base blunt, margin toothed. 

Flowers purplish to pinkish, to 0.5 cm long, nearly radially symmetrical, corolla tubular, 4 lobes, top lobe larger, notched at tip; calyx tubular, tube hairless, 5 linear lobes, with bristly margins; inflorescence of terminal spikes, beginning as oval, later elongating to 3-10 cm, flowers in crowded, whorls in nodes above two small leaf-like bracts; blooms June-Oct. 

Fruit none or sterile. 

Wetland status: FACW+. 

Frequency in NYC: Very infrequent. 

Origin: European cultigen. 

Habitat: Open wet, disturbed areas, stream banks. 

Notes: A traditional medicinal and culinary herb. Also used as a ground cover but tends to be invasive. Attractive to butterflies (PlantFinder. 2007).