Example ⟳ +
An example collection, so you can see what this page does. Nothing added here is kept: leaving deletes it.
Allium simillimum; photograph (c) Mark Pollock, some rights reserved (CC BY) CC BY(c) Mark Pollock, some rights reserved (CC BY) · observed growing wild · 2025-04-24

Allium simillimum L.F.Hend.

Simil onion

Amaryllidaceae · Idaho, Montana · listed by its family as a bulb, tuber or caudex

Add one to my plants
Sow seed
Allium simillimum, photograph (c) Emma, some rights reserved (CC BY)Allium simillimum, photograph (c) Emma, some rights reserved (CC BY)Allium simillimum, photograph (c) Mark Pollock, some rights reserved (CC BY)Allium simillimum, photograph (c) Mark Pollock, some rights reserved (CC BY)Allium simillimum, photograph (c) Mark Pollock, some rights reserved (CC BY)Allium simillimum, photograph (c) Mark Pollock, some rights reserved (CC BY) 38 photographs ›
Habitat figures
Cold floor (1 night in 100)
-20.9°C
Record low -33.9 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
24°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
778mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
11–50DLI
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 winters: the rain comes November to May, with nights below freezing; no growing season read. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Allium simillimum, the simil onion, or dwarf onion, is a plant species native to Idaho and Montana (Gallatin and Ravalli Counties). It grows on sandy soils at high elevations in the mountains, 1800–3400 m.

Quoted from Wikipedia, "Allium simillimum", CC BY-SA 4.0.

About the genus · Allium

Allium is a large genus of monocotyledonous flowering plants with 1112 accepted species, making Allium the largest genus in the family Amaryllidaceae and among the largest plant genera in the world. Many of the species are edible, and some have a long history of cultivation and human consumption such as the onion, garlic, scallions, shallots, leeks, and chives.

Quoted from Wikipedia, "Allium", CC BY-SA 4.0.

Cultivation

Grouped as a bulb, tuber or caudex, listed under the family Amaryllidaceae in the archetype table, and Kew describes it as “bulbous geophyte”.

Seasons

The rain rule reads a rainy season and no growing season: 70% of the median year's rain (570 mm of 777 mm) falls in November to May, the cooler part of the year, but the mean nightly low is below freezing in February, March, April, May, June, December and January, so the rule reads no growing season from it. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: May to November.

Rain

777 mm in the median year at the habitat, 570 mm of it November to May. Wettest month December at 108 mm, driest month August at 25 mm. Across the grid cells of the range the year's total runs 483 mm to 1,333 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 778 mm, is the year's rain at the top of the page; the 777 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 50 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 9, the highest 90th-percentile month 51).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -20.9 °C, the absolute minimum -33.9 °C, 9,075 frost nights in 44 years, 206.3 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 32.6 °C. Monthly means: the coldest month's mean nightly low -12.2 °C in December (across the grid cells of the range -16.8 °C to -8.5 °C), the warmest month's mean daily high 23.8 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -20.9 °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: 44 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 +406 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.

Group. Listed under the family Amaryllidaceae in the archetype table, and Kew describes it as “bulbous geophyte”. A group is taken only where Kew's description of the species agrees with the table's listing. The table gives no figure and no prose; the cold floor is the habitat's alone.

Climate across the habitat

Habitat months, northern hemisphere

Habitat climate of Allium simillimum through the yearWarmest months July and August, mean daily high 24 °C; coldest month December, mean nightly low -12.2 °C; 777 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°frost32.6° 99th-percentile day, NASA POWER-33.9° lowest night in 44 years, NASA POWER°C · day and nightcold quarter050100150200mm rainDLI 11–50RH 44–61%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 120 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 °C-3 / -6–1-1 / -4–33 / 0–87 / 3–1312 / 8–1818 / 15–2324 / 21–2924 / 20–2818 / 15–2311 / 7–152 / -2–6-4 / -7–0
Night °C-11 / -16–-7-10 / -15–-7-7 / -11–-3-4 / -8–0-1 / -4–44 / 1–99 / 6–148 / 5–144 / 1–9-1 / -5–3-8 / -13–-4-12 / -17–-9
Rain mm85 / 45–14269 / 37–12276 / 44–12366 / 43–11479 / 49–13065 / 30–11727 / 11–5125 / 10–4835 / 20–6455 / 34–9387 / 47–153108 / 56–168
DLI13 / 11–1520 / 18–2229 / 26–3238 / 36–4144 / 42–4648 / 45–5050 / 49–5144 / 43–4634 / 33–3623 / 21–2514 / 12–1611 / 9–13
RH %60 / 57–6459 / 57–6258 / 56–6056 / 52–5854 / 49–5651 / 46–5444 / 39–4844 / 39–4747 / 43–5052 / 49–5458 / 56–6261 / 58–64
How this section is made
Each figure is the median across the 120 grid cells holding the 178 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 928:1289 (43.575, -115.525). Over 44 years there: absolute minimum -33.9 °C, 1st-percentile night -20.9 °C, 99th-percentile day 32.6 °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 120 distinct grid cells holding 178 of the 178 in-range records; extremes and elevation at the typical cell 928:1289 (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 43.50_-115.625, lapse-corrected +406 m at 6.5 °C/km. Elevation: ETOPO 2022, 1897 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.
NativeIdaho, Montana · 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 marker44.035, -115.618 · in the densest population, 223 records (86% of those in range)
Kew's description“bulbous geophyte” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 258 georeferenced records inside the native range; the climate across the range on the 178 of them placed to within 10 km; the map shows only the 223 openly licensed ones, which alone would put the marker 18 km away. 3 records outside the WCVP native range not used. 80 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 of the 258 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Allium simillimum, photograph 1did not loadAllium simillimum, photograph 2did not loadAllium simillimum, photograph 3did not loadAllium simillimum, photograph 4did not loadAllium simillimum, photograph 5did not loadAllium simillimum, photograph 6did not load

Photographs: (c) Emma, some rights reserved (CC BY) (2); (c) Mark Pollock, some rights reserved (CC BY) (4).

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

Heuchera grossulariifolia Heuchera grossulariifolia Gooseberry-leaf alumroot Photo: CC BY, Kieran HanrahanCalochortus eurycarpus Calochortus eurycarpus White mariposa lily Photo: CC BY, Todd PattersonHackelia micrantha Hackelia micrantha Meadow stickseed Photo: CC0, author not statedCarex hoodii Carex hoodii Hood's sedge Photo: CC0, author not statedPenstemon payettensis Penstemon payettensis Payette beardtongue Photo: CC BY, Matt BergerAconitum columbianum Aconitum columbianum Columbia monkshood Photo: CC0, author not stated

Other Allium 241 in the reference

Allium acuminatum Allium acuminatum Tapertip onion Photo: CC BY-SA, Brian FinzelAllium acutiflorum Allium acutiflorum Amaryllidaceae Photo: CC BY, Nicola CrockfordAllium aflatunense Allium aflatunense Amaryllidaceae Photo: CC0, author not statedAllium akaka Allium akaka Amaryllidaceae Photo: CC BY-SA, C T Johansson Allium alexeianum Amaryllidaceae Allium altaicum Allium altaicum Altai onion Photo: CC BY, Urgamal MagsarAllium altissimum Allium altissimum Amaryllidaceae Photo: CC BY, Wolfgang AhlmerAllium altyncolicum Allium altyncolicum Altynkol Chive Photo: CC BY, Oleg KosterinAllium amethystinum Allium amethystinum Amethyst Garlic Photo: CC BY, Eleftherios KatsillisAllium ampeloprasum Allium ampeloprasum Wild Leek Photo: CC BY, Felix Blesch Allium amphibolum Amaryllidaceae Allium amplectens Allium amplectens Slim-leaved onion Photo: CC BY, Parker James Lloyd all 242 ›

Names & registers

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Amaryllidaceae
Described by
L.F.Hend.
Native to
Idaho, Montana
Wild records
258 in range · 223 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 2026-10-21
GBIF species record gbif.species answeredasked 2026-10-21
GBIF synonyms gbif.synonyms answeredasked 2026-10-21
GBIF common names gbif.vernacular answeredasked 2026-10-21names fetched 2026-10-21
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
Habitat climate climate answeredasked 2026-10-21
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-21NASA POWER (MERRA-2) daily 1981–2024, cell 43.50_-115.625, lapse-corrected +406 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-21
Wikipedia wikipedia answeredasked 2026-10-21
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 2026-10-21none of the photographs on this page is credited to GBIF: those shown are other sources', and GBIF's were the same photographs or were set aside by the photograph rules
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 16 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…