Guide
Sweet Woodruff: A Fragrant Carpet for Dry and Moist Shade
The short answer
Sweet woodruff (Galium odoratum) is a deciduous perennial groundcover for shade, forming a soft, dense carpet 6 to 12 inches tall of bright green whorled leaves topped with tiny white star flowers in spring. The foliage is sweetly fragrant when dried, and the plant is hardy across zones 4a to 9b.
Plant divisions or nursery plants about a foot apart in partial to full shade. It prefers moist soil but will survive in dry shade, and it tolerates juglone, so it grows under black walnut trees where most plants fail. One caution: in ideal moist conditions it spreads by creeping rhizomes aggressively enough to be considered invasive in Oregon, so site it where wandering is acceptable — under trees and shrubs, not in a tidy border.
Where It Works
- Partial to full shade; foliage scorches in hot sun.
- Prefers moist, organic soil but survives in dry shade under trees (Wisconsin Horticulture).
- Under large trees and shrubs — including black walnut, since it is not susceptible to juglone.
- Better behaved in cooler climates and clay soils; most aggressive in moist, loose, ideal conditions.
How to Plant It
- 1Space plants about a foot apart — Set out divisions or pots roughly 12 inches apart in spring; the creeping rhizomes will knit the patch together.
- 2Water to establish — Keep new plantings moist until rooted; established patches handle dry shade with only occasional deep watering.
- 3Propagate by division — It divides easily in spring, and clumps can be dug and moved through the growing season if kept moist until re-established (Wisconsin Horticulture).
Care and Containment
Sweet woodruff needs almost no routine care — no feeding program, and shearing after bloom is optional to refresh the mat. In hot, dry summers the foliage may brown; a trim and moisture usually bring fresh growth.
Watch its spread. In ideal moist conditions it advances by rhizome and can crowd small perennials; South Dakota State and Wisconsin extensions both describe it as aggressive in the right conditions, and it is considered invasive in Oregon. Plant it where filling every gap is a feature, and edge or pull runners where it meets beds.
⚠ Sweet woodruff can spread aggressively in moist, ideal sites and is considered invasive in Oregon. Give it a bounded shade area, or keep a spade edge between it and your borders.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Wisconsin Horticulture (UW-Madison Extension) — Sweet Woodruff, Galium odoratum — Height 6-12 inches with whorled leaves, shade preference with survival in dry shade, hardiness zones 4a-9b, spacing about a foot apart, propagation by division, aggressive spread in ideal conditions and invasive status in Oregon, juglone tolerance under walnut
- North Carolina Extension Gardener Plant Toolbox — Galium odoratum — Growth habit, shade groundcover use, and spreading rhizomatous nature
- South Dakota State University Extension — Sweet Woodruff: Attractive Groundcover for Shady Gardens — Recommendation as a shade groundcover and notes on vigorous spread