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Asteraceae family

Santa Cruz Tarplant Holocarpha macradenia

Native Specialist-bee host
Late-season nectar — Flowers in a late-autumn window when few other plants in our catalog bloom — valuable late forage for pollinators (relative to our catalog's bloom coverage).

Santa Cruz Tarplant is an annual wildflower native to the lower 48 states. It blooms Jun – Nov. A host for pollen-specialist native bees.

More about this plant

Holocarpha macradenia, commonly known as the Santa Cruz tarplant, is an endangered plant endemic to Northern California. Alternative common names for this plant are Santa Cruz tarweed or Santa Cruz sunflower. Wikipedia →

Growing & care

USDA PLANTS · TRY
Conditions
Sources · Conditions
Cold hardiness (derived) — Hardiness
Hardiness
≥ zone 11 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
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 – Nov — 41 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 →
✦ Bees specialist-bee host · 7 bee visitors

Specialist native bees depend on it.

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

Xerces pollinator conservation →

7 native & managed bee species are documented visiting Santa Cruz Tarplant :

Melissodes lupinus · long-horned bee · ✦ specialist Lasioglossum titusi · Titus' Lasioglossum Melissodes subillatus · long-horned bee · ✦ specialist Triepeolus helianthi · cuckoo bee Bombus vosnesenskii · Vosnesensky Bumble Bee Lasioglossum tegulariforme · sweat bee
+ 1 more bees →
Osmia nemoris · mason bee
Specialist hosts from Smith et al. 2024. Visitor records (observations, not exhaustive) from Noori et al. 2026 (CC BY 4.0) · GloBI → · ✦ = pollen-specialist bee (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 (16) 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 — GloBI · Smith et al. 2024 (CC BY)
[10] Conservation rank — NatureServe Explorer (CC BY)
[11] Federal ESA status — USFWS ECOS (U.S. Fish & Wildlife Service)
[12] Cold hardiness (derived) — Derived from U.S. range × USDA PHZM zones
[14] Bee specialists — Smith et al. 2024 (Zenodo, CC BY 4.0)
[15] Flower-visitor value (derived) — Noori et al. 2026 (CC BY 4.0) · GloBI
[16] 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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