Parietaria pensylvanicaMuhl. ex Willd.

Pennsylvania pellitory

WFO wfo-0000473229 Accepted WFO 2026-06 8 photographs CC BY

Plate 1 figs. a–h · 8 separate observations

Parietaria pensylvanica, photographed by Trevor Van Loon
fig. a Trevor Van Loon, CC BY 4.0 / 2022-06-10 / obs. 205958983
Parietaria pensylvanica, photographed by Marilynn Miller
fig. b Marilynn Miller, CC BY 4.0 / obs. 203379543
Parietaria pensylvanica, photographed by Ryan Sorrells
fig. c Ryan Sorrells, CC BY 4.0 / obs. 199256295
Parietaria pensylvanica, photographed by florawhite
fig. d florawhite, CC BY 4.0 / obs. 196831084
Parietaria pensylvanica, photographed by Annika Lindqvist
fig. e Annika Lindqvist, CC BY 4.0 / obs. 183285809
Parietaria pensylvanica, photographed by Colin Croft
fig. f Colin Croft, CC BY 4.0 / obs. 168920314
Parietaria pensylvanica, photographed by Ryan Sorrells
fig. g Ryan Sorrells, CC BY 4.0 / obs. 144580942
Parietaria pensylvanica, photographed by Ryan Sorrells
fig. h Ryan Sorrells, CC BY 4.0 / obs. 142046912

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
02450093
Filed as
Parietaria pensylvanica Muhl. ex Willd.
Det. by
D. E. Atha 2015-01-01
Collected
D. E. Atha 2014-06-03
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 58 botanical countries

Regions where Parietaria pensylvanica is native: Alabama, Alberta, Arizona, Arkansas, British Columbia, California, Colorado, Connecticut, District of Columbia, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Manitoba, Maryland, Massachusetts, Mexico Central, Mexico Gulf, Mexico Northeast, Mexico Northwest, Mexico Southwest, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Ontario, Oregon, Pennsylvania, Québec, Saskatchewan, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Washington, West Virginia, Wisconsin, Wyoming, Yukon AlabamaAlbertaArizonaArkansasBritish ColumbiaCaliforniaColoradoConnecticutFloridaGeorgiaIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineManitobaMarylandMassachusettsMexico CentralMexico GulfMexico NortheastMexico NorthwestMexico SouthwestMichiganMinnesotaMississippiMissouriMontanaNebraskaNevadaNew HampshireNew JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOntarioOregonPennsylvaniaQuébecSaskatchewanSouth CarolinaSouth DakotaTennesseeTexasUtahVermontWashingtonWest VirginiaWisconsinWyomingYukon District of Columbia
Native distribution of Parietaria pensylvanica, 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
Alberta ABT
Arizona ARI
Arkansas ARK
British Columbia BRC
California CAL
Colorado COL
Connecticut CNT
District of Columbia WDC
Florida FLA
Georgia GEO
Idaho IDA
Illinois ILL
Indiana INI
Iowa IOW
Kansas KAN
Kentucky KTY
Louisiana LOU
Maine MAI
Manitoba MAN
Maryland MRY
Massachusetts MAS
Mexico Central MXC
Mexico Gulf MXG
Mexico Northeast MXE
Mexico Northwest MXN
Mexico Southwest MXS
Michigan MIC
Minnesota MIN
Mississippi MSI
Missouri MSO
Montana MNT
Nebraska NEB
Nevada NEV
New Hampshire NWH
New Jersey NWJ
New Mexico NWM
New York NWY
North Carolina NCA
North Dakota NDA
Ohio OHI
Oklahoma OKL
Ontario ONT
Oregon ORE
Pennsylvania PEN
Québec QUE
Saskatchewan SAS
South Carolina SCA
South Dakota SDA
Tennessee TEN
Texas TEX
Utah UTA
Vermont VER
Washington WAS
West Virginia WVA
Wisconsin WIS
Wyoming WYO
Yukon YUK

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 91 in flower of 218 examined

Peak flowering in May. Each bar is the share of Parietaria pensylvanica 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. 91 of 218 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 5 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 2,007 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -13.0 °C 5.1 °C 7.2 °C
Warmest month, mean daily high 27.3 °C 33.7 °C 35.1 °C
Annual rainfall 680 mm 914 mm 1,228 mm
Rainfall in the driest quarter 71 mm 164 mm 265 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 2,007 research-grade observations of Parietaria pensylvanica 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 15 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.

  • Freirea pensylvanica (Muhl. ex Willd.) Jarm.
  • Helxine pennsylvanica Nieuwl.
  • Helxine pensylvanica (Muhl. ex Willd.) Nieuwl.
  • Parietaria debilis var. pensylvanica (Muhl. ex Willd.) Wedd.
  • Parietaria falcata Raf.
  • Parietaria heterophyla Raf.
  • Parietaria linguaefolia Liebm.
  • Parietaria linguifolia Liebm.
  • Parietaria obtusa Rydb.
  • Parietaria occidentalis Rydb.
  • Parietaria orizabae Liebm.
  • Parietaria pensylvanica var. microphylla Wedd.
  • Parietaria pensylvanica var. obtusa (Rydb.) Shinners
  • Parietaria rufa Raf.
  • Parietaria virgata Raf.

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.