Nabalus serpentaria(Pursh) Hook.

cankerweed

WFO wfo-1000085750 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h · 8 separate observations

Nabalus serpentaria, photographed by Bruce Slater
fig. a Bruce Slater, CC BY 4.0 / 2022-06-02 / obs. 204214108

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.

The specimen a real sheet, in a real collection

Herbarium
The New York Botanical Garden
Accession
230757
Filed as
Nabalus fraseri var. barbatus Torr. & A.Gray
Det. by
not recorded on this sheet
Collected
S. B. Buckley
Origin
US
The sheet
View the digitised specimen (CC BY 4.0)

A real pressed plant, in a real collection, under the accession number above. Not an illustration of one. The holding institution does not serve this sheet’s image to third parties, so there is no photograph here. The record is real and the link goes to it. Where we hold no openly licensed sheet for a species this section is simply absent, and where a sheet never recorded who determined it, that field stays empty rather than being filled in. Roughly half of all herbarium sheets never recorded a determiner, which is ordinary.

Native range 20 botanical countries

Regions where Nabalus serpentaria is native: Alabama, Connecticut, Delaware, District of Columbia, Florida, Georgia, Kentucky, Maryland, Massachusetts, Mississippi, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode I., South Carolina, Tennessee, Virginia, West Virginia AlabamaConnecticutFloridaGeorgiaKentuckyMarylandMassachusettsMississippiNew JerseyNew YorkNorth CarolinaOhioPennsylvaniaSouth CarolinaTennesseeVirginiaWest Virginia DelawareDistrict of ColumbiaRhode I.
Native distribution of Nabalus serpentaria, 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. Regions too small to draw at this scale are marked with a dot.
RegionTDWG codeContinent
Alabama ALA NORTHERN AMERICA
Connecticut CNT
Delaware DEL
District of Columbia WDC
Florida FLA
Georgia GEO
Kentucky KTY
Maryland MRY
Massachusetts MAS
Mississippi MSI
New Jersey NWJ
New York NWY
North Carolina NCA
Ohio OHI
Pennsylvania PEN
Rhode I. RHO
South Carolina SCA
Tennessee TEN
Virginia VRG
West Virginia WVA

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 66 in flower of 131 examined

Proportion of examined Nabalus serpentaria in flower, by month
Month In flower Examined Share 95% interval
Jan 0 0 too few examined
Feb 0 0 too few examined
Mar 0 1 too few examined
Apr 0 18 0% 0% to 18%
May 0 5 0% 0% to 43%
Jun 0 8 0% 0% to 32%
Jul 0 4 too few examined
Aug 1 6 17% 3% to 56%
Sep 39 53 74% 60% to 84%
Oct 24 33 73% 56% to 85%
Nov 2 3 too few examined
Dec 0 0 too few examined

Peak flowering in Sep. Each bar is the share of Nabalus serpentaria 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. 66 of 131 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 6 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 524 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -5.5 °C -1.3 °C 5.3 °C
Warmest month, mean daily high 26.7 °C 30.5 °C 32.2 °C
Annual rainfall 1,030 mm 1,220 mm 1,551 mm
Rainfall in the driest quarter 210 mm 261 mm 328 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 524 research-grade observations of Nabalus serpentaria 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 16 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.

  • Nabalus albus var. serpentaria (Pursh) Torr.
  • Nabalus fraseri DC.
  • Nabalus fraseri var. fraseri
  • Nabalus fraseri var. integrifolius (Cass.) Torr. & A.Gray
  • Nabalus integrifolius Cass.
  • Nabalus serpentaria var. integrifolius Britton
  • Nabalus serpentaria var. laevis DC.
  • Nabalus serpentarius (Pursh) Hook.
  • Nabalus serpentarius subsp. integrifolius (Cass.) Britton
  • Nabalus serpentarius var. laevis DC.
  • Nabalus serpentarius var. serpentarius
  • Prenanthes glauca Raf.
  • Prenanthes integrifolia (Cass.) Small
  • Prenanthes serpentaria Pursh
  • Prenanthes serpentaria f. serpentaria
  • Prenanthes serpentaria var. serpentaria

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. USDA PLANTS Database. common name, checklist symbol PRSE. public domain. 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.