Pycnanthemum tenuifolium
narrowleaf mountainmint
Overview
Pycnanthemum tenuifolium, narrowleaf mountainmint, is an upright perennial in the mint family, 1-3 feet (30-90 cm) tall, forming a bushy clump of slender, branching stems clothed in very narrow, almost needle-like leaves 1-2 inches (2.5-5 cm) long. The smooth green foliage carries a strong spearmint scent when crushed, and the square stems mark it clearly as a mint. From midsummer into early fall the branch tips are crowded with flat clusters of many tiny white flowers dotted with purple, set among small whitened bracts. These flowers draw a wide range of bees, wasps, flies, and butterflies in large numbers, often supporting dozens of insect species in pollinator surveys. It is native to dry to moist prairies, open woods, fields, and roadsides across the eastern and central United States, on a wide range of soils. The plant spreads by short rhizomes into broad clumps, slowly enough to stay manageable but enough to need occasional dividing. It tolerates drought, heat, clay, and poor soil, though it can flop in rich ground or heavy shade and self-sows into open ground. The minty foliage holds through the season and the whitened bracts keep some interest after bloom.
Native Range
Pycnanthemum tenuifolium is native to the eastern and central United States, from New England and the Great Lakes south to the Gulf states and west to the eastern Great Plains. It grows in prairies, open woods, old fields, and along roadsides on dry to moist soils.Suggested Uses
Pycnanthemum tenuifolium is used in pollinator and native gardens, prairies, meadows, and the middle of mixed borders. Its long bloom feeds bees, wasps, and butterflies, and the minty foliage is avoided by deer and rabbits.How to Identify
Appearance
Size & Dimensions
Height1' - 3'
Width/Spread1' - 2'
Bloom Information
Flowering runs from July into September, the small white flowers opening a few at a time across each flat cluster over many weeks. The whitened bracts beneath the flowers add to the pale look and persist after the flowers fade. Bloom is long and steady through the heat of summer.
Detailed Descriptions
Flower Description
white with purple dotsFoliage Description
greenGrowing Conditions
Sun Requirements
Requires 5-9 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grow Pycnanthemum tenuifolium in full sun to part shade in average, well-drained soil with a pH of about 5.5 to 7.5; it adapts to dry, moist, clay, and lean soils alike. It tolerates drought and heat once established and needs little water or feeding. Rich soil and shade produce taller stems that may flop, so a sunnier, leaner spot keeps it upright. Plants spread by rhizomes into wide clumps and can be divided in spring to control size or make more plants. Cutting back in late spring produces a denser, shorter habit.Pruning
Cut the dead stems to the ground in late winter or early spring. Shearing by a third in late spring keeps plants compact and less likely to flop. Dividing every few years controls the spreading clump.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
early springlate spring
Container Growing
✓ Suitable for container growing
Minimum container size: 2 gallons