Pycnanthemum tenuifolium

Common Names

Narrowleaf Mountain Mint, Slender Mountain Mint, Mountain Mint, Virginia Thyme, Common Horsemint

Summary

Narrowleaf mountain mint (Pycnanthemum tenuifolium) is a herbaceous perennial native to eastern North America, including Ontario, with a stiff, erect, clumping habit about 2–3 feet tall and extremely narrow, needle-like leaves that emit a minty aroma when crushed. It bears small white flowers (often with pale lavender tones) in mid- to late summer, forming terminal clusters and serving as a nectar source that attracts bees and butterflies while spreading rhizomatically to form dense populations. It grows in full sun to partial shade in well-drained soils ranging from dry to moist, tolerating a range of conditions and drought once established; hardy in USDA zones 4–8; typically spaced about 12–18 inches apart with a total spread of 12–24 inches; maintenance is low, with division every few years and deadheading to limit self-seeding; deer- and rabbit-resistant, it enhances pollinator, native plant, rain, rock, and meadow landscapes and can aid erosion control, though it may spread aggressively and is best confined by hardscape elements; propagation by seed (germinates without pretreatment) or by cuttings (best in June) or division during dormancy.

Lifecycle

Perennial

Height

24-36 inches

Spread

24-36 inches

Hardiness Zones

Zones 4-8

Sunlight Requirements

Ideally full Sun; tolerates Partial Sun and Partial Shade.

Soil Type

Well-drained soil

Soil Drainage

Well-drained soil

Soil pH

Acidic, pH below 6.0

Bloom Color

White

Bloom Time

Summer to Fall

Foliage Color

Green, Light green

Fall Foliage Color

Green

Leaf Lifecycle

Deciduous

Growth Rate

Rapid growth with quick rhizome spreading and aggressive expansion

Seasons of Interest

Spring, Summer, Fall, Winter

Propagation Methods

Seeds, Cuttings, Division

Attracts Wildlife

Bees, Butterflies, Other pollinators