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Scrophulariaceae family

Splitleaf Indian Paintbrush Castilleja rhexiifolia

Native

Splitleaf Indian Paintbrush is a perennial shrub native to Canada and the lower 48 states. It blooms Jun – Aug.

More about this plant

Castilleja rhexiifolia, commonly called rosy paintbrush, subalpine paintbrush, or rhexia-leaved paintbrush, is a species of plant in Orobanchaceae, commonly known as the broomrape family. They are a common flower found in moist habitats near or above timberline in the Rocky Mountains and the Pacific Northwest. Like most members of the Castilleja genus, they are partially parasitic plants. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
Cold hardiness (derived) — Hardiness
Hardiness
≥ zone 6 derived from its U.S. range
Size & form
Sources · Size & form
USDA PLANTS — Lifespan
McKenzie et al. 2025 — community-science image analysis (MIT) — Flower colour
Lifespan
Perennial
Flower colour
Red AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
In the garden
Shrub layer — Sits in the shrub of a layered food forest or polyculture.Open guide →
derived roles
AI = read by an AI vision model · DERIVED = a computed estimate, not a direct measurement. The “How we know this” section below details each.
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 · Jun – Aug — 165 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 ~5 caterpillar species

Castilleja supports ~5 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 Castilleja in North America, including:

Amblyptilia pica · Geranium Plume Moth Argyrotaenia franciscana · Orange Tortrix Charidryas palla · brush-footed butterfly Endothenia hebesana · Verbena Bud Moth Euphydryas anicia · Anicia Checkerspot Euphydryas chalcedona · Variable Checkerspot
+ 8 more species →
Euphydryas editha · Bay Checkerspot Euphydryas gillettii · brush-footed butterfly Eupithecia anticaria · geometer (inchworm) moth Eupithecia nimbicolor · geometer (inchworm) moth Grammia nevadensis · Nevada Tiger Moth Grammia oithona · tiger moth Heliothis oregonica · Oregon Gem Heliothis proruptus · owlet 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 6 bee visitors
Visitor records (observations, not exhaustive) from Noori et al. 2026 (CC BY 4.0) · GloBI →
Wildlife & visitors 1 nectaring

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

1 adult butterfly & moth species is recorded nectaring at its flowers:

Boloria eunomia · Bog Fritillary
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 (1) Methods & honest limits
Flower colour Derived

McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.

Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.

McKenzie, P., Berardi, A.E., Hopkins, R. (2025). flower_color_phenology (MIT).
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 (18) 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] Wetland indicator — USACE National Wetland Plant List (2022)
[08] Description — Wikipedia (CC BY-SA)
[09] Ecological value — Warren II 2026 (CC0) · Tallamy host-use counts
[11] Conservation rank — NatureServe Explorer (CC BY)
[12] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[13] Wildlife & visitors — GloBI — Global Biotic Interactions (CC0)
[16] Flower-visitor value (derived) — Noori et al. 2026 (CC BY 4.0) · GloBI
[17] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[18] Caterpillar species — NHM HOSTS (CC0)
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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