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Cyperaceae family

Mertens' Sedge Carex mertensii

Native
Deer-resistant — Low palatability to browsing deer. Usually passed over, but no plant is truly deer-proof when food is scarce.

Mertens' Sedge is a perennial grass native to Alaska, Canada, and the lower 48 states. It grows to 3.5 ft and blooms May in full sun, with brown fruit.

More about this plant

Carex mertensii is a species of sedge known by the common name Mertens' sedge. It is native to western North America from Alaska to California to Montana, where it grows in moist and wet habitat in mountain forests and meadows. This sedge produces clumps of stems reaching maximum heights between 80 and 120 centimeters. The leaves are small; those toward the bases of the stems are reduced to sheaths only. The inflorescence is a densely packed, bullet shaped cluster of overlapping flowers, mainly hanging on long peduncles. Each inflorescence is generally 2 to 4 centimeters long. Each of the flowers has a dark-colored bract. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
USDA PLANTS — Sun · Soil & moisture
USDA — SoilPH — Soil pH
USDA PLANTS (DwCA, Zenodo 17903503) — Fertility Requirement / Soil Adaptation — Fertility need · Adapts to
USDA — Temp-Min °F — Hardiness
Sun
Full sun
Soil & moisture
Medium moisture
Soil pH
6–7.7
Fertility need
Low
Adapts to
Coarse (sandy), Medium (loam)
Hardiness
USDA zone 5+
Size & form
Sources · Size & form
USDA PLANTS (DwCA, Zenodo 17903503) — Height, Mature — Height
USDA PLANTS (DwCA, Zenodo 17903503) — Planting Density (per acre) — Spacing
USDA PLANTS (DwCA, Zenodo 17903503) — Growth Rate / Spread / Growth Form / Lifespan / Active Growth Period / Seed Period — Spread · Growth rate · Growth form · Active growth
USDA PLANTS — Lifespan
TRY Plant Trait Database (CC BY 4.0) · USDA PLANTS — Foliage
USDA PLANTS (DwCA, Zenodo 17903503) — Fruit/Seed Color / Fruit Persistence — Fruit
Height
3.5 ft
Spacing
1.5–2 ft apart from USDA planting density
Spread
Slow
Growth rate
Slow
Growth form
Rhizomatous
Lifespan
Perennial · short-lived
Foliage
Broadleaf · medium texture
Active growth
Spring & summer
Fruit
Brown
In the garden
Sources · In the garden
USDA PLANTS (DwCA, Zenodo 17903503) — Propagation Method / Commercial Availability — Propagate by · In the trade
USDA PLANTS (DwCA, Zenodo 17903503) — Germination (cold stratification) — Seed starting
USDA PLANTS — Seed Period — Seeds ripen
USDA PLANTS (DwCA, Zenodo 17903503) — Foliage Texture / Browse Palatability / Resprout — Deer browsing · Resprouts if cut
Propagate by
Seed, Bare root, Sprigs
Seed starting
No stratification needed
Seeds ripen
Spring – Summer seed-collection / harvest window
In the trade
Contract growing only
Deer browsing
Low often deer-resistant
Resprouts if cut
No
Shrub layer — Sits in the shrub of a layered food forest or polyculture.Open guide →
derived roles
The garden year bloom → fruit → fall colour
J
F
M
A
M
J
J
A
S
O
N
D
Bloom
Bloom (the flower's colour)
Bloom · May — USDA PLANTS (DwCA, Zenodo 17903503) — BloomPeriod
When to sow · for your area

Sow timing keys off your local last- and first-frost dates.

Species characteristics from USDA PLANTS (public domain) + TRY (CC BY) — general guidance, not a guarantee for your exact site. Deer "browsing" is documented palatability, not a deer-proof claim.

Wildlife & pollinators

How pollinator value is scored →
❧ Caterpillar hosts ~36 caterpillar species

Carex supports ~36 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 strong genus.

Recorded feeding on Carex in North America, including:

Aletia oxygala · owlet moth Amphipoea americana · American Ear Moth Amphipoea interoceanica · Interoceanic Ear Moth Amphipoea velata · owlet moth Apamea finitima · owlet moth Apamea indocilis · Ignorant Apamea
+ 8 more species →
Biselachista cucullata · grass-miner moth Celaena reniformis · owlet moth Chortodes inquinata · owlet moth Cingilia catenaria · Chain-Dotted Geometer Cosmopterix clemensella · cosmet moth Cosmopterix ebriola · cosmet moth Cosmopterix fernaldella · cosmet moth Ctenucha brunnea · Brown Ctenucha
Keystone count (genus-level) from Warren II 2026 (CC0) · Tallamy host-use records. Named species (a documented Nearctic sample, not exhaustive) from NHM HOSTS (CC0).
Species thumbnails re-hosted from iNaturalist — Creative Commons, credited per image (hover for credit). Click any species to see it on iNaturalist. Not exhaustive; many taxa have no openly-licensed photo yet.
How we know this (2) Methods & honest limits
Photosynthesis Direct fact

A recorded categorical fact: each species is tagged C3 (standard), C4 (heat/water-efficient) or CAM (succulent, night-time CO₂ uptake) — or a facultative combination. We only show a trait card for the noteworthy C4/CAM cases; C3 is the unremarkable majority, kept in the data but not surfaced as a card.

Kattge, J. et al. TRY plant trait database — Categorical Traits Dataset (2012).
Climate niche (heat tolerance & native rainfall) Derived

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.

Realized-niche / climate-envelope approach (Pearson & Dawson 2003; Soberón 2007). Climate: NOAA NCEI nClimDiv county normals (1991–2020).
Derived values are computed from open data by a published method — labelled, cited, and never shown as a direct observation. Full methodology →
Sources for this entry (31) Open & cited
[01] Scientific name & family — USDA PLANTS (DwCA, Zenodo 17903503)
[02] Growth habit & duration — USDA PLANTS (DwCA, Zenodo 17903503)
[03] Native status & distribution — USDA PLANTS (DwCA, Zenodo 17903503)
[04] Common name — USDA PLANTS (via GBIF)
[18] Invasive / introduced status — USDA PLANTS (DwCA, Zenodo 17903503) — native status
[19] Wetland indicator — USACE National Wetland Plant List (2022)
[21] Description — Wikipedia (CC BY-SA)
[22] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts
[23] Conservation rank — NatureServe Explorer (CC BY)
[25] Functional traits — TRY Plant Trait Database (CC BY 4.0)
[26] Photosynthetic pathway — TRY Plant Trait Database (CC BY 4.0)
[27] Climate niche — Derived — realized climate niche from U.S. county occurrences (GBIF) × NOAA NCEI county climate normals 1991–2020 (public domain)
[29] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[30] Caterpillar species — NHM HOSTS (CC0)
[31] County range — GBIF Open Data — open-licensed occurrences (CC0/CC-BY) → county
Spot an error or have a better photo? Every field links to its source, and the whole dataset is open.
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).

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