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Alnus serrulata; photograph (c) Brandon Corder, some rights reserved (CC BY) CC BY(c) Brandon Corder, some rights reserved (CC BY) · observed growing wild · 2026-09-07

Alnus serrulata (Aiton) Willd.

Hazel alder; Smooth alder; Brookside alder; Common alder

Betulaceae · Nova Scotia, Québec +30

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Alnus serrulata, photograph (c) Cyrus Harp, some rights reserved (CC BY-SA)Alnus serrulata, photograph (c) Cyrus Harp, some rights reserved (CC BY-SA)Alnus serrulata, photograph (c) Cyrus Harp, some rights reserved (CC BY-SA)Alnus serrulata, photograph (c) Anne Parker, some rights reserved (CC BY)Alnus serrulata, photograph (c) Anne Parker, some rights reserved (CC BY)Alnus serrulata, photograph (c) Anne Parker, some rights reserved (CC BY) 91 photographs ›
Habitat figures
Cold floor (1 night in 100)
-11.1°C
Record low -24.0 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
30°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
1,279mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
14–40DLI
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
Rain spread: 70% of the median year's rain takes 9 months, so no short rainy season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Alnus serrulata, the hazel alder or smooth alder, is a thicket-forming shrub in the family Betulaceae. It is native to eastern North America and can be found from western Nova Scotia and southern New Brunswick south to Florida and Texas.

Quoted from Wikipedia, "Alnus serrulata", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (977 mm of 1,258 mm) takes 9 months, March to September and November to December. Mean temperature moves 22.8 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: September to March and May to June.

Rain

1,258 mm in the median year at the habitat, 977 mm of it March to September and November to December. Wettest month July at 120 mm, driest months (2 at 93 mm). Across the grid cells of the range the year's total runs 1,114 mm to 1,519 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,279 mm, is the year's rain at the top of the page; the 1,258 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: 14 to 40 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 11, the highest 90th-percentile month 41).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -11.1 °C, the absolute minimum -24.0 °C, 3,964 frost nights in 44 years, 90.1 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 37.9 °C. Monthly means: the coldest month's mean nightly low -0.7 °C in January (across the grid cells of the range -6.7 °C to 4.0 °C), the warmest month's mean daily high 30.4 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -11.1 °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: 56 to 60% 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 +2 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 Alnus serrulata through the yearWarmest months July and August, mean daily high 30 °C; coldest month January, mean nightly low -0.7 °C; 1,258 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°frost37.9° 99th-percentile day, NASA POWER-24.0° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125150mm rainDLI 14–40RH 56–60%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 1176 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 °C8 / 2–1410 / 4–1615 / 8–2020 / 14–2424 / 19–2829 / 24–3130 / 26–3330 / 26–3226 / 22–2920 / 16–2514 / 10–199 / 4–14
Night °C-1 / -7–41 / -6–64 / -2–99 / 4–1314 / 9–1819 / 15–2121 / 17–2321 / 17–2317 / 13–2011 / 7–156 / 2–101 / -3–5
Rain mm93 / 74–13693 / 71–143112 / 92–146104 / 85–129109 / 91–144112 / 99–138120 / 101–147106 / 84–133104 / 89–12595 / 80–127104 / 82–131106 / 83–146
DLI16 / 13–1821 / 19–2228 / 25–3035 / 32–3738 / 36–4040 / 39–4038 / 38–4134 / 33–3829 / 27–3223 / 20–2617 / 13–1914 / 11–16
RH %58 / 56–6057 / 55–5956 / 55–5756 / 54–5758 / 56–6059 / 58–6160 / 58–6260 / 58–6359 / 57–6158 / 57–5958 / 57–5959 / 57–60
How this section is made
Each figure is the median across the 1176 grid cells on land that hold in-range records (1428 records in those cells; 2 more cells hold records but no land by the elevation layer, so those records sit at sea and the cells are left out), 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 1050:2033 (37.475, -78.325). Over 44 years there: absolute minimum -24.0 °C, 1st-percentile night -11.1 °C, 99th-percentile day 37.9 °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 1176 distinct grid cells holding 1428 of the 1430 in-range records (2 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 1050:2033 (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 37.50_-78.125, lapse-corrected +2 m at 6.5 °C/km. Elevation: ETOPO 2022, 108 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.
NativeNova Scotia, Québec, Illinois, Missouri, Oklahoma, Connecticut, Indiana, Maine, Massachusetts, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., Vermont, West Virginia, Texas, Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, District of Columbia · 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 marker33.801, -84.314 · in the densest population, 994 records (55% of those in range)
Kew's description“shrub” · “subtropical” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 1800 georeferenced records inside the native range; the climate across the range on the 1428 of them in the land cells it reads, of 1430 placed to within 10 km; the map shows only the 620 openly licensed ones, which alone would put the marker 511 km away. 14 records outside the WCVP native range not used. 370 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 1800 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Alnus serrulata, photograph 1did not loadAlnus serrulata, photograph 2did not loadAlnus serrulata, photograph 3did not loadAlnus serrulata, photograph 4did not loadAlnus serrulata, photograph 5did not loadAlnus serrulata, photograph 6did not load

Photographs: (c) Cyrus Harp, some rights reserved (CC BY-SA) (3); (c) Anne Parker, some rights reserved (CC BY) (3).

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

Tipularia discolor Tipularia discolor Cranefly orchid Photo: CC BY, Heather Gottfried LloydLespedeza procumbens Lespedeza procumbens Trailing lespedeza Photo: CC0, author not statedGentiana saponaria Gentiana saponaria Soapwort gentian Photo: CC BY, Anne ParkerHypericum mutilum Hypericum mutilum Dwarf St. Johnswort Photo: CC0, author not statedSolidago erecta Solidago erecta Showy goldenrod Photo: CC BY, Justin DonahueAletris farinosa Aletris farinosa White colicroot Photo: CC0, author not stated

Other Alnus 28 in the reference

Alnus acuminata Alnus acuminata Alder Photo: CC BY-SA, Carlo BresciaAlnus alnobetula Alnus alnobetula Green alder Photo: CC BY, Mary KriegerAlnus cordata Alnus cordata Italian alder Photo: CC BY, Sabarni SarkerAlnus cremastogyne Alnus cremastogyne Betulaceae Photo: CC BY-SA, Kenraiz, Krzysztof ZiarnekAlnus fauriei Alnus fauriei Betulaceae Photo: CC BY, Marco MussitaAlnus firma Alnus firma Japanese green alder Photo: CC BY, Kim, Hyun-taeAlnus formosana Alnus formosana Formosan Alder Photo: CC0, author not statedAlnus glutinosa Alnus glutinosa Black alder Photo: CC BY, Stanislav MurashkinAlnus hirsuta Alnus hirsuta Manchurian alder Photo: CC BY, Violetta DzizyurovaAlnus incana Alnus incana Grey alder Photo: CC BY, Ann RedmondAlnus japonica Alnus japonica Japanese alder Photo: CC BY, Tatyana PetrenkoAlnus jorullensis Alnus jorullensis Mexican alder Photo: CC BY, Favian Flores Medina all 29 ›

Names & registers

Also known as Alnus americana; Alnus autumnalis; Alnus glutinosa subsp. obtusifolia; Alnus glutinosa var. autumnalis; Alnus glutinosa var. oblongata and 23 more. (GBIF Backbone)

Under another author Alnus rubra Desf. and Alnus rubra Desf. ex Corrie and Alnus rubra Desf. ex Steud. is an older name of this species, not Alnus rubra, a species of the reference. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Betulaceae
Described by
(Aiton) Willd.
Native to
Nova Scotia, Québec, Illinois +29
Wild records
1800 in range · 620 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; 44 records within 1 km of a botanic garden, herbarium or zoo left out (38 at a botanic garden or arboretum, 1 at a herbarium, 5 at a zoo; Wikidata's list)
Habitat climate climate answeredasked 2026-10-21
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-21NASA POWER (MERRA-2) daily 1981–2024, cell 37.50_-78.125, lapse-corrected +2 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 2026-10-21
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 102 datasets via GBIF.org; each carries its own licence.

Cultifolio

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