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Callitrichaceae family

Twoheaded Water-starwort Callitriche heterophylla

Native
Also known as: Two-headed water-starwort

Twoheaded Water-starwort is an annual wildflower native to Alaska, Canada, and Greenland. It grows to 0.3 ft and blooms Apr in part shade – shade, with green fruit.

More about this plant

Callitriche heterophylla, commonly called twoheaded water-starwort, is a species of flowering plant in the family Plantaginaceae. It is native to North America, where it found in the north from Greenland to Alaska, south to Mexico. It is widespread in the United States. Its natural habitat is in a wide variety of wetlands, including ponds, streams, and mudflats. It is typically found in areas of still or slow moving water. 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
Part shade – shade
Soil & moisture
High moisture
Soil pH
5.2–6.8
Fertility need
Medium
Adapts to
Medium (loam), Fine (clay)
Hardiness
USDA zone 4+
Size & form
Sources · Size & form
TRY Plant Trait Database (CC BY 4.0) — 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
0.3 ft
Spacing
6–8 ft apart from USDA planting density
Spread
Moderate
Growth rate
Rapid
Growth form
Single crown
Lifespan
Annual · short-lived
Foliage
Broadleaf · fine texture
Active growth
Spring through autumn
Fruit
Green
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 — Resprouts if cut
Propagate by
Seed, Sprigs
Seed starting
No stratification needed
Seeds ripen
Summer – Autumn seed-collection / harvest window
In the trade
No known commercial source
Resprouts if cut
No
Ground-cover layer — Sits in the ground-cover of a layered food forest or polyculture.Open guide →
Rain garden / bioswale — Rated OBL on the wetland list — tolerates wet feet, so it suits the soggy zone of a rain garden or bioswale that catches and filters runoff.Open guide →
Living mulch / groundcover — Low, ground-hugging grower — can carpet bare soil as a living mulch, shading out weeds and holding moisture.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 · Apr — 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.
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 (30) 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)
[17] Invasive / introduced status — USDA PLANTS (DwCA, Zenodo 17903503) — native status
[18] Wetland indicator — USACE National Wetland Plant List (2022)
[20] Description — Wikipedia (CC BY-SA)
[21] Ecological value — GloBI
[22] 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] Other common names — Wikidata (CC0)
[30] County range — GBIF Open Data — open-licensed occurrences (CC0/CC-BY) → county
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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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