Pycnanthemum incanum aka Silverleaf Mountain Mint

Pycnanthemum incanum is a perennial herb in the mint family. Gardeners know it as hoary mountain mint or silverleaf mountain-mint. It comes from the eastern United States, reaching west to Illinois. It grows in dry woods and thickets within that range. Its name refers to the gray cast of its leaves. This plant dies back rather than keeping its leaves year-round.

In gardens, it often stands 2–3 feet [0.61–0.91 m] tall. Some plants reach 6 feet [1.83 m], according to NC State. Allow a width of 2–4 feet [0.61–1.22 m]. Many branches rise from upright, square stems with pale hairs. The leaves grow in pairs along the stems. They have stalks, toothed edges, and an egg-like or narrow shape. Soft white hairs coat their lower sides. The upper leaves and flower bracts also look pale. Crushed plant parts release a strong scent like spearmint.

Small flowers form clusters at stem tips and upper leaf joints. Each flower has two lips and a white to lavender tint. Purple spots mark the lower lip. Pale bracts sit just below the blooms. Sources place flowering between June and October, with July–September reported by Missouri Botanical Garden. Bees, butterflies, moths, and other insects visit the flowers for nectar. The plant also feeds wavy-lined emerald moth larvae. NC State lists small black capsules that show in September and October.

Grow this mint in sun or part shade. Full sun gives the best flower display. It needs soil that drains well and accepts dry to moist ground. NC State notes a preference for moist soil. It also withstands drought and suits USDA zones 4–8. Care needs are low, but its spread needs watching. Long rhizomes, rooting stems, and seeds help it form colonies. Cut through spreading roots with a spade in spring to limit clumps. Division and seed both offer ways to raise more plants.

Use it in native gardens, dry meadows, or woodland settings. It also suits herb gardens and borders where spread stays checked. Its growth can help hold soil against erosion. Deer tend to leave it alone. Sources report no major pest or disease issues. Leaves and flowers have uses in tea, including dried leaves. PFAF records folk uses for headaches, stomach trouble, and fevers. These records do not establish treatment safety or benefit. PFAF lists no known hazards, but gives no specific pet-safety evidence.