Pycnanthemum muticum

Etymology

Pycnanthemum is derived from the Greek “pyknos” meaning dense and “anthos” meaning flower, describing the densely packed flower clusters; muticum is Latin, meaning blunt.

Native Habitat

Meadows, fields, low woodland areas.

Garden Uses

Best grown en masse to highlight the effect of the fabulous silvery bracts, and to maximize pollinator accessibility. Can be used as a border plant, ideal for pollinator gardens as well as cottage gardens or meadows that are designed to allow the plants to naturalize. Due to its spreading nature, it is well-suited for stabilizing slopes. Generally pest and disease-free, though it can succumb to rust.

Overview

Clustered mountain-mint is a perennial native to Eastern North America, found from Maine (rare) to Michigan and Illinois in the north, and from Missouri to Florida and Texas in the south. This clump-forming plant is commonly found in open places such as grassy meadows and low woodlands, and along woodland edges, but occasionally can be found in dry upland woods. It prefers to grow in full to part sun, ideally in moist or medium-damp soils, and is the least drought tolerant of this genus. While the plant can tolerate bright shade, it blooms best in full sun. Clustered mountain mint spreads via shallow-rooted rhizomes but is not aggressive like many true mints (Mentha genus).

Leaves and Stems

The 1-3” long leaves are simple, almost sessile, ovate to lanceolate, acuminate (pointed), with round or heart-shaped bases and toothed margins. The foliage is very strongly scented of mint. The leaves grow in opposite arrangement along branching stems that are square-sided, as is typical of the mint family.

Flowers

Tiny (approximately 1/4” in length), lipped, tubular white-pink flowers bloom from July to September in densely packed, flat-topped, mostly terminal clusters. The flowers appear delicately spotted with pinkish-purple dots, and are lobed, with 3 lobes on the lower lip, 2 on the upper lip. The clusters are surrounded by shining, silvery-white leafy bracts. When massed, this shimmering, frosted effect is quite striking.

Fruit/Seed

Tiny brown oval seeds ripen in late fall, but remain nestled within the dried flower heads throughout the winter.

Animal Associates

This is an excellent pollinator plant attracting a multitude of bees, wasps, flies, and butterflies. The plant serves as a host for the wavy-lined emerald moth (Synchlora aerata) and for the gray hairstreak butterfly (Strymon melinus). A pollinator plant trial at Penn State held in 2013 assessed 88 species and ranked clustered mountain-mint as the number one species for attracting a diversity of pollinators. Due to its high essential oil content, browsers such as deer and rabbits tend to leave clustered mountain-mint alone.