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Brassicaceae family

MacDonald Rockcress Arabis macdonaldiana

Native Specialist-bee host

MacDonald Rockcress is a perennial wildflower native to the lower 48 states. It blooms May. A host for pollen-specialist native bees.

More about this plant

Arabis mcdonaldiana is a species of flowering plant in the mustard family known by the common name McDonald's rockcress. It is native to northern California and Oregon, where it grows on newly exposed, barren serpentine soils in openings in temperate coniferous forest habitat. It is a rare and endangered plant known from several sites in California and approximately two occurrences in Oregon, where it is threatened mainly by mining, particularly of nickel, which is one of several metals plentiful in the serpentine. On September 29, 1978, this was the second plant to be federally listed as an endangered species. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
Cold hardiness (derived) — Hardiness
Hardiness
≥ zone 9 derived from its U.S. range
Size & form
Sources · Size & form
USDA PLANTS — Lifespan
Lifespan
Perennial
In the garden
Herb layer — Sits in the herb 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 — 10 obs · Herbarium specimens — Park et al. 2023 (CC BY 4.0)
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 ~7 caterpillar species

Arabis supports ~7 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 Arabis in North America, including:

Anthocharis sara · Sara Orangetip Colias occidentalis · Western Sulphur Euchloe ausonides · Large Marble Euchloe creusa · Northern Marblewing Euchloe hyantis · California Marble Euchloe olympia · Olympia Marble
+ 8 more species →
Hellula rogatalis · Cabbage Webworm Moth Paramidea lanceolata · white / sulphur butterfly Paramidea midea · white / sulphur butterfly Pieris napi · Green-Veined White Pieris virginiensis · West Virginia White Pontia beckerii · Becker's White Pontia occidentalis · Western White Pontia protodice · Checkered White
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. Arabis 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 (11) 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
[06] Description — Wikipedia (CC BY-SA)
[07] 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
[10] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[11] 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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