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Liliaceae family

Welsh Onion Allium fistulosum

Native

Welsh Onion is a perennial wildflower native to Canada. It grows to 1.6 ft.

More about this plant

Allium fistulosum, the Welsh onion, also commonly called bunching onion, long green onion, Japanese bunching onion, stone leek, rock onion and spring onion, is a species of perennial plant, often considered to be a kind of scallion. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
Cold hardiness (derived) — Hardiness
Hardiness
≥ zone 5 derived from its U.S. range
Size & form
Sources · Size & form
TRY Plant Trait Database (CC BY 4.0) — Height · Foliage
USDA PLANTS — Lifespan
Height
1.6 ft
Lifespan
Perennial
Foliage
Evergreen broadleaf
In the garden
Herb layer — Sits in the herb of a layered food forest or polyculture.Open guide →
derived roles
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 ~21 caterpillar species

Allium supports ~21 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 moderate genus.

Recorded feeding on Allium in North America, including:

Actebia fennica · owlet moth Aglossa caprealis · Meal Moth Agrotis gladiaria · Swordsman Dart Agrotis ipsilon · Dark Sword-Grass Agrotis malefida · Rascal Dart Agrotis orthogonia · Pale Western Cutworm
+ 8 more species →
Archips argyrospila · Fruit-Tree Leafroller Moth Autographa californica · Alfalfa Looper Moth Cadra cautella · Fig-Moth Cadra figulilella · snout moth Cryptoblabes gnidiella · snout moth Discestra trifolii · owlet moth Ephestia elutella · snout moth Estigmene acrea · Salt Marsh Moth
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).
✦ Bees 15 bee visitors
Visitor records (observations, not exhaustive) from Noori et al. 2026 (CC BY 4.0) · GloBI →
Wildlife & visitors 1 mammal · 8 nectaring

Open records of who else uses Welsh Onion — a generalist food-web signal, kept separate from the keystone Ecological Value.

Recorded eaten by 1 mammal species (fruit, seed, browse):

Ovis aries · Domestic Sheep

8 adult butterfly & moth species are recorded nectaring at its flowers — the most-recorded:

Pelopidas sinensis Papilio canadensis · Canadian Tiger Swallowtail Papilio cresphontes · Eastern Giant Swallowtail Papilio glaucus Argynnis paphia · Silver-Washed Fritillary Adela australis
Interaction records (observations, not exhaustive) from GloBI → (CC0). Counts are distinct species; names are the most-recorded. Common names from Wikidata (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
Leaf build Direct fact

We read each species’ measured specific leaf area (leaf area per unit dry weight) from the Global Spectrum dataset and band it: thin & fast (high SLA), medium, or thick & tough (low SLA). The global median is about 10 mm²/mg.

Honest limits: A species-mean from pooled measurements — individual plants vary with light and site. A broad strategy signal, not a precise per-plant figure.

Díaz, S. et al. (2022) The global spectrum of plant form and function: enhanced species-level trait dataset. Scientific Data 9:755.
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).
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 (22) 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)
[05] Invasive / introduced status — US-RIIS v2.0 (USGS)
[07] Description — Wikipedia (CC BY-SA)
[08] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts
[11] Functional traits — TRY Plant Trait Database (CC BY 4.0)
[12] Photosynthetic pathway — TRY Plant Trait Database (CC BY 4.0)
[13] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[14] Wildlife & visitors — GloBI — Global Biotic Interactions (CC0)
[19] Flower-visitor value (derived) — Noori et al. 2026 (CC BY 4.0) · GloBI
[20] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[21] Caterpillar species — NHM HOSTS (CC0)
[22] 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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