Tawny Cottongrass Eriophorum virginicum
Tawny Cottongrass is a perennial grass native to Canada, the lower 48 states, and Saint-Pierre & Miquelon. It grows to 3.9 ft and blooms Jul – Aug in part shade – shade, with black fruit.
More about this plant
Eriophorum virginicum, the tawny cottongrass, is a species of flowering plant in the sedge family Cyperaceae. It is native to eastern North America but was introduced into both British Columbia and Washington in western North America. It is most common in eastern Canada, New England, and the Great Lakes region. It is the only species of Eriophorum in North America that occurs in the southeastern United States, where it is uncommon. The common name refers to the tawny color of its fruiting head. Despite the name, it is a sedge, not a grass, and it is sometimes called tawny cottonsedge to emphasize this fact. Wikipedia →
Growing & care
USDA PLANTS · TRY- Sun
- Part shade – shade
- Soil & moisture
- Medium moisture
- Soil pH
- 3.8–6.5
- Fertility need
- Low
- Adapts to
- Coarse (sandy), Medium (loam), Fine (clay)
- Hardiness
- USDA zone 4+
- Height
- 3.9 ft
- Spacing
- 3–4 ft apart from USDA planting density
- Spread
- None — clumping
- Growth rate
- Moderate
- Growth form
- Single crown
- Lifespan
- Perennial · moderate
- Foliage
- Broadleaf · medium texture
- Active growth
- Summer
- Fruit
- Black persists into winter
- Flower colour
- Brown AI AI image-analysis of community-science photos — lower-confidence (a more subjective call, often an inconspicuous flower); not a botanical record
- Propagate by
- Seed, Sprigs
- Seed starting
- No stratification needed
- Seeds ripen
- Summer – Autumn seed-collection / harvest window
- In the trade
- No known commercial source
- Deer browsing
- Medium moderately palatable
- Resprouts if cut
- No
Sow timing keys off your local last- and first-frost dates.
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~1 caterpillar species
Eriophorum supports ~1 caterpillar species.
Native butterfly & moth caterpillars are the base of the terrestrial food web — most songbirds rear their young almost entirely on them. As a host for native Lepidoptera this is a modest genus.
Recorded feeding on Eriophorum in North America, including:
Related plants
More Eriophorum →
How we know this (2) Methods & honest limits
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.
Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.
Sources for this entry (31) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
Loading…
BibTeX
Loading…