Erigeron filifoliusNutt.

threadleaf fleabane

WFO wfo-0000062869 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Erigeron filifolius, photographed by machaut2
fig. a machaut2, CC BY 4.0 / 2022-06-10 / obs. 205054780

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Native range 8 botanical countries

Regions where Erigeron filifolius is native: British Columbia, California, Idaho, Montana, Nevada, Oregon, Utah, Washington British ColumbiaCaliforniaIdahoMontanaNevadaOregonUtahWashington
Native distribution of Erigeron filifolius, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows.
RegionTDWG codeContinent
British Columbia BRC NORTHERN AMERICA
California CAL
Idaho IDA
Montana MNT
Nevada NEV
Oregon ORE
Utah UTA
Washington WAS

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Flowering 221 in flower of 291 examined

Proportion of examined Erigeron filifolius in flower, by month
Month In flower Examined Share 95% interval
Jan 0 9 0% 0% to 30%
Feb 0 6 0% 0% to 39%
Mar 0 6 0% 0% to 39%
Apr 3 7 43% 16% to 75%
May 58 86 67% 57% to 76%
Jun 85 88 97% 90% to 99%
Jul 53 56 95% 85% to 98%
Aug 9 9 100% 70% to 100%
Sep 5 11 45% 21% to 72%
Oct 3 4 too few examined
Nov 5 7 71% 36% to 92%
Dec 0 2 too few examined

Peak flowering in Aug. Each bar is the share of Erigeron filifolius observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 221 of 291 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 2 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Where it actually grows measured, from 1,115 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -9.7 °C -6.2 °C -1.9 °C
Warmest month, mean daily high 25.3 °C 28.3 °C 32.5 °C
Annual rainfall 216 mm 358 mm 688 mm
Rainfall in the driest quarter 21 mm 51 mm 85 mm

It is found where winters bring hard frost. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 1,115 research-grade observations of Erigeron filifolius that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one. Climate from CHELSA V2.1 (Karger et al. 2017); occurrences from 10.15468/dl.cgje2x.

Also published as 4 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Chrysopsis canescens DC.
  • Diplopappus filifolius Hook.
  • Erigeron filifolius var. robustior M.Peck
  • Erigeron filifolius var. typicus Cronquist

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.