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Onagraceae family

Selfing Willowherb Epilobium cleistogamum

Native

Selfing Willowherb is an annual wildflower native to the lower 48 states. It blooms Apr – Jul.

More about this plant

Epilobium cleistogamum is a species of willowherb known by the common name selfing willowherb. This plant is endemic to central California where it is a resident of vernal pools and mudflats. It is a small annual plant with fuzzy pointed green leaves. Some of the leaves have hairs which are knobby and gland-tipped. The flowers are usually cleistogamous, that is, they self-pollinate without opening. Some of the flowers do open to reveal pinkish-purple to nearly white, deeply notched petals. The fruit is a tough four-sided capsule about a centimeter long. 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 →
Rain garden / bioswale — Rated OBL on the wetland list — tolerates wet feet, so it suits the soggy zone of a rain garden or bioswale that catches and filters runoff.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 · Apr – Jul — 45 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 ~32 caterpillar species

Epilobium supports ~32 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 strong genus.

Recorded feeding on Epilobium in North America, including:

Acronicta oblinita · Smeared Dagger Moth Albuna pyramidalis · Fireweed Clearwing Moth Alypia langtoni · owlet moth Amphion floridensis · Nessus Sphinx Androloma maccullochii · Macculloch's Forester Anticlea multiferata · Many-Lined Carpet
+ 8 more species →
Dichomeris washingtoniella · twirler moth Ecliptopera silaceata · Small Phoenix Ecliptoptera silaceata · geometer (inchworm) moth Eudryas brevipennis · owlet moth Eudryas unio · Pearly Wood-Nymph Eulia ministrana · leafroller moth Eulithis destinata · geometer (inchworm) moth Eulithis diversilineata · Lesser Grapevine Looper 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).
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 (15) 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] Caterpillar host count — Warren II 2026 (Dryad, CC0) · Tallamy host-use counts
[14] Caterpillar species — NHM HOSTS (CC0)
[15] County range — GBIF Open Data — open-licensed occurrences (CC0/CC-BY) → county
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