FIRST IMPRESSIONS: Pycnanthemum flexuosum is an aromatic perennial wildflower. This mint relative bears oval toothed leaves on strong square stems. In summer, plants are topped by dense frizzy ball-like clusters of tiny white to lavender tubular flowers. Pollinators flock to the blooms in moist meadows or sunny gardens with average well drained soil.
HABITAT & HARDINESS: Pycnanthemum flexuosum occurs in the coastal plain from Virginia to northern Florida and west to Alabama and Mississippi.
Pycnanthemum flexuosum occurs in wet pine savannas, low pinelands, edges of pocosins, borders of cypress gum swamps, open marshes, bogs, openings in bottomland forests and pine barrens. Plants generally occur in association with pines (including longleaf pine), oak, cypress and sweetgum. This species also persists in sites that are regularly burned.
Plants are hardy from USDA Zones 5-8.
PLANT DESCRIPTION: Pycnanthemum flexuosum is an upright perennial that expands slowly from shallow rhizomes.
The sturdy square stems are covered with fine white hairs. They branch freely in the upper half.
Aromatic leaves are arranged opposite from each other on short petioles along the stems.
The blades are toothed or occasionally entire with pointed tips. They are lanceolate or narrowly elliptical and up to 2” long and about ½” wide. In autumn blades often develop red coloration along the margins.
The stems terminate in globular white to pale lavender dense head-like flower cymes. Many fragrant tubular florets are packed into the 1-1.5” wide inflorescence. Each floret is about ¼” long with a ring of united petals that is lobed toward the tip.
Blooming lasts for about 6 weeks from mid-summer to early autumn. The florets mature into ovoid nutlets that are nestled into brown button-like cymes.
Plants grow 2-3’ tall with 3-4’ spread.
CULTURAL & MAINTENANCE NEEDS: Pycnanthemum flexuosum thrives in sunny sites with moist well drained soil. Plants tolerate part sun, clay, seasonally wet soils, heat, humidity and drought.
Throngs of desirable pollinators flock to the blooms. The aromatic foliage is unpalatable to deer and plants are fairly resistant to other pests.
This species will slowly expand to form colonies. Since it is not aggressive, little maintenance is needed.
In manicured gardens, stems can be trimmed to the ground in late winter.
LANDSCAPE USES: The mountain mints are listed on many “Top Ten Plants for Pollinators” lists. Pycnanthemum flexuosum is a good choice for a Wildlife Garden or Meadow. Plants are also used as Butterfly Nectar Plants, Cut Flowers or as part of a Grouping or Mass Planting that will aid in Erosion Control. This species has Showy Blooms and is appropriate for Cottage Gardens, Deer Resistant Plantings, Water-wise Landscapes, Low Maintenance Plantings, Rain Gardens, Rock Gardens and Perennial Borders.
COMPANION & UNDERSTUDY PLANTS: Try pairing Pycnanthemum flexuosum with Monarda bradburiana, Rudbeckia hirta, Liatris spicata, Schizachyrium scoparium or Andropogon gerardii.
Pycnanthemum incanum has similar appearance and culture and could be substituted in some situations.
TRIVIA: The dense head-like flower cymes make this plant a pollinator paradise. Native bees, beneficial wasps, flies, beetles, skippers and small butterflies (especially hairstreaks) frequent the blossoms. Plants host gray hairstreak caterpillars. The aromatic foliage is unpalatable to deer, rabbits and other herbivores.
Also known as Koellia hugeri, Koellia hyssopifolia and Pycnanthemum hyssopifolium