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Asteraceae family

Romerillo (var. radiata) Bidens alba var. radiata variety

Native Specialist-bee host

Romerillo (var. radiata) is an annual wildflower native to the lower 48 states, U.S. outlying islands, and Puerto Rico. A host for pollen-specialist native bees.

More about this plant

Bidens alba is a species of flowering plant in the family Asteraceae, commonly known as shepherd's needles, beggarticks, Spanish needles, or butterfly needles. Bidens means two- toothed, describing the two projections found at the top of the seeds, and alba refers to the white ray florets. This plant is found in tropical and subtropical regions of North America, Asia, South America, and Africa, situated in gardens, road sides, farm fields and disturbed sites. B. alba is an annual or short-lived perennial, which is considered a weed in the United States. However, B. alba leaves are edible and can be used as medicinal remedies. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
Cold hardiness (derived) — Hardiness
Hardiness
≥ zone 7 derived from its U.S. range
Size & form
Sources · Size & form
USDA PLANTS — Lifespan
Lifespan
Annual
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 ~15 caterpillar species

Bidens supports ~15 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 Bidens in North America, including:

Agonopterix atrodorsella · concealer moth Charidryas gorgone · brush-footed butterfly Cirrhophanus triangulifer · Goldenrod Stowaway Condica concisa · owlet moth Condica cupentia · Splotched Groundling Condica mobilis · Mobile Groundling
+ 8 more species →
Epiblema otiosana · Bidens Borer Homoeosoma electella · Sunflower Moth Homoeosoma electellum · snout moth Lacinipolia basiplaga · owlet moth Lorita abornana · leafroller moth Mescinia estrella · snout moth Nathalis iole · Dainty Sulphur Neumoegenia poetica · Poetry 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 specialist-bee host

Specialist native bees depend on it.

Some native bees are pollen specialists (oligolectic) — they raise young only on pollen from particular plant genera. Bidens is a recorded specialist-bee host, so losing it can mean losing the bee that relies on it.

Xerces pollinator conservation →
Specialist hosts from Smith et al. 2024.
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.
Sources for this entry (12) 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 — USDA PLANTS (DwCA, Zenodo 17903503) — native status
[07] Description — Wikipedia (CC BY-SA)
[08] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts · Smith et al. 2024 (CC BY)
[09] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[11] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[12] Caterpillar species — NHM HOSTS (CC0)
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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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