Smooth Phlox, Phlox glaberrima

Smooth Phlox

Phlox glaberrima

Sun Shade:
Bloom Time: Summer
Zones: 4, 5
Soil Conditions: Clay, Loam, Sand
Soil Moisture: Medium, Moist
Color: Pink, Purple
Fragrance: Yes
Height: 2 -4 feet
Spacing: 2 - 4 feet


Smooth Phlox (Phlox glaberrima) typically occurs in moist meadows, low woods and along riverbanks. It is an upright, clump-forming, rhizomatous perennial which typically grows 1-3 feet tall. Sweetly-aromatic, tubular, 5-lobed, rose to reddish purple flowers (to 1 inch across) with long corolla tubes are densely arranged in large, pyramidal, terminal clusters (panicles to 12 inch long) atop stiff, upright stems that seldom need staking. This is one of the few tall phloxes to bloom in spring. Very thin, opposite, finely-toothed, lance-shaped, dark green leaves (to 4 inch long). As the common name suggests, this plant is essentially hairless.

The blooming period can occur from late spring to late summer, lasting about 1-2 months. The flowers are replaced by narrow seed capsules. Each capsule contains many small seeds. The root system consists of a taproot. This plant spreads by re-seeding itself.

Habitats include moist black soil prairies, moist sand prairies, cemetery prairies, prairie remnants along railroads, openings in bottomland woodlands, thickets, acidic gravelly seeps, and abandoned fields. This is an indicator plant of higher quality prairie remnants – the showy flowers can be spotted from some distance away.

Easily grown in moderately fertile, medium moisture, well-drained soil in full sun to light shade. Prefers moist, organically rich soils in full sun. Plants are intolerant of drought and need to be watered in dry spells. Tolerates more soil moisture than most other species of phlox. Also tolerates hot and humid summer weather. Can slowly spread over time by both slender rhizomes and self-seeding to form large colonies.

Plant Notes and Herbal Uses
  There is a tendency to sprawl, unless this plant is supported by grass and other kinds of vegetation.
  Young plants can be killed by summer heat and drought.
  Remove faded flower panicles to prolong bloom period.
  If not deadheaded, plants will self-seed in optimum growing conditions.
Further Information

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