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Lepidium densiflorum; photograph (c) Norma Malinowski, some rights reserved (CC BY) CC BY(c) Norma Malinowski, some rights reserved (CC BY) · observed growing wild · 2026-09-15

Lepidium densiflorum Schrad.

Miner's pepperwort; Prairie peppergrass; Prairie pepperweed; Common pepperweed

Brassicaceae · Alaska, Northwest Territories +59

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Lepidium densiflorum, photograph (c) Евгений Маринкин, some rights reserved (CC BY)Lepidium densiflorum, photograph (c) Norma Malinowski, some rights reserved (CC BY)Lepidium densiflorum, photograph (c) Natalia Kazakova, some rights reserved (CC BY)Lepidium densiflorum, photograph (c) Natalia Kazakova, some rights reserved (CC BY)Lepidium densiflorum, photograph (c) Марина Давлетшина, some rights reserved (CC BY)Lepidium densiflorum, photograph (c) Марина Давлетшина, some rights reserved (CC BY) 64 photographs ›
Habitat figures
Cold floor (1 night in 100)
-21.4°C
Record low -33.7 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
28°C
Jul at the habitat CHELSA
Rain a year (median across the range)
767mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
11–42DLI
Lowest to highest month (DLI) CHELSA
The year in your months, northern hemisphere
  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug
  9. Sep
  10. Oct
  11. Nov
  12. Dec
Wet summers: the rain comes April to October, read as a summer growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Lepidium densiflorum is a species of flowering plant in the mustard family known by the common names common pepperweed, prairie peppergrass, elongate peppergrass, hairy-fruited peppergrass, and large-fruited peppergrass.

Quoted from Wikipedia, "Lepidium densiflorum", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads a summer growing season: 70% of the median year's rain (571 mm of 762 mm) falls in April to October, warmer than the year (wet-season mean 16.0 °C against a yearly mean of 8.8 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: October to April.

Rain

762 mm in the median year at the habitat, 571 mm of it April to October. Wettest month June at 99 mm, driest month January at 29 mm. Across the grid cells of the range the year's total runs 320 mm to 1,220 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 767 mm, is the year's rain at the top of the page; the 762 mm here is the median year's, the twelve monthly medians added, which the rain rule reads. Habitat calendar, northern hemisphere; median year across the grid cells of the range, CHELSA.

Light

Open sky over the habitat: 11 to 42 mol/m²/day across the year (daily light integral, median year across the grid cells of the range, CHELSA; the lowest 10th-percentile month across the cells is 7, the highest 90th-percentile month 50).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -21.4 °C, the absolute minimum -33.7 °C, 6,660 frost nights in 44 years, 151.4 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 37.8 °C. Monthly means: the coldest month's mean nightly low -8.9 °C in January (across the grid cells of the range -15.4 °C to -1.4 °C), the warmest month's mean daily high 27.9 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -21.4 °C, which is the 1st-percentile night over 44 years at a typical spot in the range (NASA POWER).

Humidity

Relative humidity at the habitat: 54 to 61% across the year (monthly means, median year across the grid cells of the range, CHELSA). A figure about the air, saying nothing about how the plant takes water.

How this section is made

Each card states this species' habitat figures with their sources, and what two fixed rules read from them; nothing here says what the plant does, wants or tolerates. The rules · the terms.

Seasons. Read from the median year of CHELSA monthly rainfall and mean temperature across the grid cells of the range: the rain rule takes the smallest set of months carrying 70% of the rain and calls it winter when its mean is more than half a degree below the year's, summer when more than that above, and neither in between; the temperature rule, used only under 120 mm, names the cooler six months when they are at least a degree cooler than the other six. Months are shifted for the other hemisphere only where the temperature curve moves 4 °C or more and the habitat lies 10° or more from the equator. A reading of the curves, not an observation of the plant.

Rain. CHELSA monthly precipitation, median year across the grid cells of the range. The rain that falls where the species is recorded; nothing about how the plant takes water.

Light. CHELSA shortwave radiation at each envelope cell, a daily-mean flux taken to a daily total and converted at 2.07 mol of PAR per MJ. The sky over the habitat, measured; what reaches a plant under a rock, a shrub or a shade cloth is not.

Temperature. NASA POWER daily minima and maxima over 44 years at a typical spot in the range, lapse-corrected +70 m to its elevation; CHELSA monthly means, median year across the grid cells of the range. The cold floor is the 1st-percentile night named in its sentence. Not a measured survival limit for any plant in a pot.

Humidity. CHELSA relative humidity, median year across the grid cells of the range.

Climate across the habitat

Habitat months, northern hemisphere

Habitat climate of Lepidium densiflorum through the yearWarmest month July, mean daily high 28 °C; coldest month January, mean nightly low -8.9 °C; 762 mm of rain in the median year (the twelve monthly medians added). Medians across the range, from CHELSA; the extremes at the edge from NASA POWER. Habitat months, northern hemisphere.-40°-20°0°20°40°frost37.8° 99th-percentile day, NASA POWER-33.7° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125150mm rainDLI 11–42RH 54–61%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 227 habitat cells, CHELSA cold quarter: the three months around the coldest month's mean nightly low extremes over 44 years at a typical spot in the range, from NASA POWER, marked at the edge, in no month DLI, mol/m²/dayRH %each on its own scale
Figures by month
JanFebMarAprMayJunJulAugSepOctNovDec
Day °C0 / -7–82 / -5–118 / 1–1615 / 8–2120 / 15–2525 / 20–3028 / 24–3227 / 23–3223 / 18–2815 / 10–217 / 1–141 / -6–8
Night °C-9 / -15–-1-8 / -13–0-3 / -8–43 / -2–99 / 3–1414 / 9–1918 / 12–2217 / 12–2113 / 7–176 / 1–11-1 / -7–5-7 / -13–-1
Rain mm29 / 11–8831 / 12–8346 / 20–9866 / 23–10786 / 28–12799 / 22–12890 / 20–11786 / 18–11380 / 22–11064 / 23–10849 / 16–10136 / 13–106
DLI13 / 9–1919 / 16–2427 / 24–3334 / 31–4238 / 36–4741 / 38–5042 / 37–5037 / 33–4429 / 24–3620 / 15–2713 / 9–2011 / 7–16
RH %60 / 54–6659 / 54–6457 / 54–6054 / 51–5755 / 50–5856 / 47–5957 / 45–6057 / 45–6056 / 48–6157 / 51–6158 / 53–6361 / 55–67
How this section is made
Each figure is the median across the 227 grid cells holding the 229 in-range records, with the 10th–90th percentile span across those cells after the slash where it differs. A dash is a month one or more of those cells has no figure for in the grid (a variable CHELSA does not carry there), so no median is taken rather than one over fewer cells. Extremes and elevation were read at a typical spot in the range, cell 954:1639 (42.275, -98.025). Over 44 years there: absolute minimum -33.7 °C, 1st-percentile night -21.4 °C, 99th-percentile day 37.8 °C. Normals: CHELSA V2.1 1981–2010 climatology, 0.05° cells (each the mean of ~36 1 km pixels). Across the range: median and 10th–90th percentile of each month across the 227 distinct grid cells holding 229 of the 229 in-range records; extremes and elevation at the typical cell 954:1639 (its coldest month's mean nightly low nearest the median across cells); its position is the cell centre. Extremes: NASA POWER (MERRA-2) daily 1981–2024, cell 42.50_-98.125, lapse-corrected +70 m at 6.5 °C/km. Elevation: ETOPO 2022, 583 m (cell mean).

Natural habitat

Native range as published by WCVP; the marker is where the records are densest and decides nothing: the climate was read across the cells of the in-range records placed well enough to read one, not at the marker.
Openly licensed records inside the range, framed on where they fall.
NativeAlaska, Northwest Territories, Yukon, Alberta, British Columbia, Manitoba, Saskatchewan, Labrador, New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward I., Québec, Idaho, Montana, Oregon, Washington, Wyoming, Iowa, Kansas, Minnesota, Missouri, North Dakota, Nebraska, Oklahoma, South Dakota, Wisconsin, Connecticut, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., West Virginia, Arizona, California, Nevada, Utah, New Mexico, Texas, Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Virginia, District of Columbia, Mexico Northeast, Mexico Northwest · introduced: Denmark, Finland, Great Britain, Norway, Sweden, Austria, Belgium, Czechoslovakia, Germany, Hungary, Poland, Switzerland, France, Spain, Italy, Romania, Sicilia, Belarus, Baltic States, Krym, Central European Russia, East European Russia, North European Russia, South European Russia, Northwest European Russia, Ukraine, Altay, Buryatiya, Chita, Irkutsk, Krasnoyarsk, Tuva, West Siberia, Yakutskiya, Amur, Kamchatka, Khabarovsk, Magadan, Primorye, Sakhalin, Kazakhstan, Tadzhikistan, North Caucasus, China South-Central, Inner Mongolia, Manchuria, China North-Central, Mongolia, Japan, Korea, Hawaii, Colorado, Illinois, Vermont, Tennessee, Argentina Northeast, Argentina Northwest · regions are the level-3 units of the World Geographical Scheme for Recording Plant Distributions, as Kew's World Checklist records ranges, some under historical names such as Yugoslavia or Czechoslovakia (how).
Map marker37.369, -95.5 · in the densest population, 88 records (20% of those in range)
Kew's description“annual or biennial” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 450 georeferenced records inside the native range; the climate across the range on the 229 of them placed to within 10 km; the map shows only the 303 openly licensed ones, which alone would put the marker 1842 km away. 1296 records outside the WCVP native range not used. 221 in-range records are placed to worse than 10 km, or with no stated accuracy (admitted only as a person's observation to three decimals), and stay on the map but off the climate.
How this section is made
The map marker: the openly licensed record nearest the middle of the densest 1° population inside the densest 4° block of the 450 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Lepidium densiflorum, photograph 1did not loadLepidium densiflorum, photograph 2did not loadLepidium densiflorum, photograph 3did not loadLepidium densiflorum, photograph 4did not loadLepidium densiflorum, photograph 5did not loadLepidium densiflorum, photograph 6did not load

Photographs: (c) Евгений Маринкин, some rights reserved (CC BY); (c) Norma Malinowski, some rights reserved (CC BY); (c) Natalia Kazakova, some rights reserved (CC BY) (2); (c) Марина Давлетшина, some rights reserved (CC BY) (2).

Similar habitat climate The 6 nearest by mean daily high, mean nightly low and rain, month by month. How.

Salix amygdaloides Salix amygdaloides Peach-leaf willow Photo: CC0, author not statedJuncus dudleyi Juncus dudleyi Dudley's rush Photo: CC BY, Anders HastingsSolidago rigida Solidago rigida Stiff goldenrod Photo: CC BY, Sandy WolkenbergLysimachia hybrida Lysimachia hybrida Mississippi loosestrife Photo: CC0, author not statedChenopodiastrum simplex Chenopodiastrum simplex Maple-leaved goosefoot Photo: CC0, author not statedVerbena stricta Verbena stricta Hoary vervain Photo: CC0, author not stated

Other Lepidium 33 in the reference

Lepidium africanum Lepidium africanum African pepperwort Photo: CC0, author not statedLepidium apetalum Lepidium apetalum Peppergrass Photo: CC BY, Urgamal MagsarLepidium austrinum Lepidium austrinum Southern pepperweed Photo: CC BY, IDClaireLepidium banksii Lepidium banksii Coastal Peppercress Photo: CC0, author not statedLepidium bidentatum Lepidium bidentatum Kunana pepperwort Photo: CC BY, Kevin FaccendaLepidium bipinnatifidum Lepidium bipinnatifidum Wayside Pepperwort Photo: CC BY, Raúl A. Ruiz M.Lepidium bonariense Lepidium bonariense Argentine pepperwort Photo: CC BY, pedrogarabayaLepidium campestre Lepidium campestre Field pepperwort Photo: CC BY, Jo RobertsLepidium chichicara Lepidium chichicara Brassicaceae Photo: CC0, Alfredo F. Fuentes ClarosLepidium coronopus Lepidium coronopus Greater swinecress Photo: CC0, author not statedLepidium didymum Lepidium didymum Lesser swinecress Photo: CC BY, ShaunLepidium draba Lepidium draba Hoary cress Photo: CC0, author not stated all 34 ›

Names & registers

Also known as Lepidium densiflorum subsp. densiflorum; Lepidium densiflorum subsp. neglectum; Lepidium densiflorum var. densiflorum; Lepidium densiflorum var. elongatum; Lepidium densiflorum var. macrocarpum and 14 more. (GBIF Backbone)

Under another author Lepidium ruderale Richardson is an older name of this species, not Lepidium ruderale, a species of the reference. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Brassicaceae
Described by
Schrad.
Native to
Alaska, Northwest Territories, Yukon +58
Wild records
450 in range · 303 open

Every figure here is derived from public data by a stated rule and names its source; nothing about this species is written for its page by a person or by AI, apart from the marked, credited quotations. How →

Where this page came from built 2026-10-22
GBIF species record gbif.species answeredasked 2026-10-22
GBIF synonyms gbif.synonyms answeredasked 2026-10-22
GBIF common names gbif.vernacular answeredasked 2026-10-22names fetched 2026-10-22
WCVP native range wcvp.distribution answeredas of 2026-06-04
GBIF occurrence records gbif.occurrences answeredas of 2026-10-21GBIF occurrence download https://doi.org/10.15468/dl.hbdw64, of 2026-10-21; 44 records within 1 km of a botanic garden, herbarium or zoo left out (24 at a botanic garden or arboretum, 2 at a herbarium, 18 at a zoo; Wikidata's list)
Habitat climate climate answeredasked 2026-10-22
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-22NASA POWER (MERRA-2) daily 1981–2024, cell 42.50_-98.125, lapse-corrected +70 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22
Wikipedia wikipedia answeredasked 2026-10-22
iNaturalist photographs, wild inat.photos.wild answeredasked 2026-10-22from iNaturalist's open data of 2026-09-27: research-grade observations with an open-licence photograph, the 24 whose photographs iNaturalist received last (the open data holds no votes); filled 2026-10-22
iNaturalist photographs, cultivated inat.photos.cultivated not asked
GBIF media gbif.media answeredasked 2026-10-22
OpenAlex papers openalex not askednot yet asked for this reference; a later fill takes the papers from OpenAlex's snapshot

Every source is recorded as having answered, reported nothing, refused, failed, not been asked, or answered twice where one answer is taken (“not taken: two items answered”), and, for a source asked when this page was built, when: the figures are as the source held them that day; a source read from a file (Kew's World Checklist, a GBIF download) says "as of" the file's day instead; a row carried from an earlier build of the page names that build instead. Only “nothing to report” is ever shown as an absence. Records came from 191 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…