Ilex opaca Aiton
American Holly, American holly, Christmas Holly, Ittohissishalokpa
Every figure on this page is derived from public data by a stated rule and says its source; nothing here is written by a person or a model, except the Wikipedia passage, which is quoted and marked as such. How it is made.
Summary
Ilex opaca, the American holly, is a species of holly, native to the eastern and south-central United States, from coastal Massachusetts south to central Florida, and west to southeastern Missouri and eastern Texas.
Text from Wikipedia, “Ilex opaca”, CC BY-SA 4.0, quoted as written. Kept separate from everything derived here.
About the genus · Ilex
Ilex or holly is a genus of over 570 species of flowering plants in the family Aquifoliaceae, and the only living genus in that family. Ilex has the most species of any woody dioecious angiosperm genus. The species are evergreen or deciduous trees, shrubs, and climbers from tropics to temperate zones worldwide. More on Wikipedia ›
The opening of Wikipedia, “Holly”, CC BY-SA 4.0, quoted as written.
At a glance
Also known as Ageria opaca (Aiton) Raf.; Ilex americana Lam.; Ilex aquifolium Marshall; Ilex aquifolium var. opaca (Aiton) Laurentius; Ilex canadensis Marshall and 13 more.
Cultivation
Its year Rain rule: no season, 70% of the rain takes 8 months (March to September and December in the northern hemisphere).
This species’ habitat figures, and what two fixed rules read from them.
The rain rule reads no season: 70% of the year's rain (847 mm of 1206 mm) takes 8 months, March to September and December. Mean temperature moves 23.2 °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 June.
Read from the median year of CHELSA monthly rainfall and mean temperature across the envelope cells: 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 gives a season to reverse. A reading of the curves, not an observation of the plant.
Rain Habitat rain 1206 mm a year, wettest July at 117 mm, driest February at 85 mm (habitat calendar, northern hemisphere).
This species’ habitat figures, with their source.
1206 mm a year at the habitat, 847 mm of it March to September and December. Wettest month July at 117 mm, driest February at 85 mm. Across the envelope cells the year's total runs 1096 mm to 1466 mm (10th to 90th percentile of each cell's own year) (median year across the envelope cells, CHELSA; habitat calendar, northern hemisphere).
CHELSA monthly precipitation, median year across the envelope cells. The rain that falls where the species is recorded; nothing about how the plant takes water.
Light Open sky over the habitat: 13 to 40 mol/m²/day.
This species’ habitat figures, with their source.
Open sky over the habitat: 13 to 40 mol/m²/day across the year (daily light integral, median year across the envelope cells, CHELSA; the lowest 10th-percentile month across the cells is 11, the highest 90th-percentile month 41).
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.
Warmth and air Cold floor -10.4 °C (1st-percentile habitat night, NASA POWER).
This species’ habitat figures, with their source.
Coldest: the 1st-percentile night over 44 years at the typical cell is -10.4 °C, the absolute minimum -21.1 °C, about 81 frost nights a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 35.1 °C. Monthly means: coldest night -1.1 °C in January (across the envelope cells -4.9 °C to 5.7 °C), warmest day 29.9 °C in July (median year across the envelope cells, CHELSA). Cold floor: -10.4 °C, which is the 1st-percentile night over 44 years at the typical cell (NASA POWER).
NASA POWER daily minima and maxima 1981–2024 at the typical cell, lapse-corrected to its elevation; CHELSA monthly means, median year across the envelope cells, CHELSA. The cold floor is the figure named in its sentence. Not a measured survival limit for any plant in a pot.
Relative humidity at the habitat: 56 to 60% across the year (monthly means, median year across the envelope cells, CHELSA). A figure about the air, saying nothing about how the plant takes water.
CHELSA relative humidity, median year across the envelope cells.
The figures the cards read from are in Climate below, and where they came from in Natural habitat.
Climate across the habitat
Figures by month
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Day °C | 7 / 3–15 | 9 / 4–17 | 13 / 8–21 | 19 / 14–25 | 23 / 20–29 | 28 / 24–31 | 30 / 27–32 | 29 / 26–32 | 25 / 22–30 | 20 / 16–25 | 14 / 11–20 | 8 / 5–16 |
| Night °C | -1 / -5–6 | -0 / -4–7 | 4 / -0–10 | 9 / 5–14 | 14 / 10–18 | 19 / 16–22 | 21 / 18–24 | 21 / 18–24 | 17 / 14–21 | 11 / 8–16 | 6 / 3–11 | 1 / -2–7 |
| Rain mm | 89 / 74–123 | 85 / 71–134 | 107 / 90–136 | 97 / 80–121 | 106 / 88–132 | 109 / 96–144 | 117 / 99–154 | 108 / 88–143 | 104 / 87–127 | 94 / 77–117 | 91 / 78–124 | 99 / 80–134 |
| DLI | 15 / 13–18 | 20 / 19–23 | 27 / 26–30 | 34 / 32–37 | 38 / 36–40 | 40 / 39–41 | 38 / 38–40 | 34 / 34–37 | 29 / 27–31 | 23 / 20–26 | 16 / 14–20 | 13 / 11–16 |
| RH % | 57 / 56–59 | 57 / 55–58 | 56 / 55–58 | 56 / 54–58 | 58 / 56–60 | 59 / 57–62 | 60 / 57–63 | 60 / 58–64 | 59 / 58–62 | 58 / 57–59 | 58 / 57–59 | 58 / 56–60 |
Each figure is the median across the 1390 grid cells holding the 1852 in-range records, with the 10th–90th percentile span across those cells after the slash where it differs. Extremes and elevation were read at the typical cell 1015:2071 (39.225, -76.425). Over 44 years there: absolute minimum -21.1 °C, 1st-percentile night -10.4 °C, 99th-percentile day 35.1 °C. Normals: CHELSA V2.1 1981–2010 climatology, 0.05° cells (each the mean of ~36 1 km pixels). Envelope: median and 10th–90th percentile of each month across the 1390 distinct grid cells holding the 1852 in-range records; extremes and elevation at the typical cell 1015:2071 (its coldest month's mean night nearest the median across cells); its position is the cell centre. Extremes: NASA POWER (MERRA-2) daily 1981–2024, cell 39.00_-76.250, lapse-corrected -19 m at 6.5 °C/km. Elevation: ETOPO 2022, 2 m (cell mean).
Natural habitat
Photographs
Photographs: no rights reserved · CC0 (8).
Photographs: iNaturalist did not answer when this page was built; what is shown came from the sources that did.
Papers naming this species
Works whose title or abstract names Ilex opaca, most cited first, from OpenAlex (CC0). A mention, not a cultivation source: nothing on this page is drawn from them.
Related
Similar habitat climate the 6 species whose habitat climate is nearest this one's: mean day and night, month by month, and rain on a log scale, in calendar order, so a habitat with the same seasons six months out is far, not near. Nothing else counts: not range, not family.
Hibiscus moscheutos Common Rose-mallow
Oenothera fruticosa Narrow-leaf Evening-primrose
Cephalanthus occidentalis Button-willow
Cercis canadensis Canada redbud
Magnolia tripetala Umbrella Magnolia
Iris cristata crested irisOther Ilex 9 in the reference
Ilex aquifolium English holly
Ilex cassine Cassena Holly
Ilex cornuta Chinese holly
Ilex crenata Box-leaf Holly
Ilex decidua Deciduous Holly
Ilex glabra Appalachian tea
Ilex rotunda Kurogane holly
Ilex verticillata American winterberry
Ilex vomitoria Appalachian tea History & registers
Where this page came from built 2026-09-20 · dossier v2 · node
gbif.species answeredcarried from build of 2026-09-19 (offline re-derivation; the backbone was not asked)gbif.synonyms answeredcarried from build of 2026-09-19 (offline re-derivation; the backbone was not asked)gbif.vernacular answeredcarried from build of 2026-09-19 (offline re-derivation; the backbone was not asked)wcvp.distribution answeredgbif.occurrences answeredGBIF occurrence download https://doi.org/10.15468/dl.3h4zamclimate answeredwikidata answeredcarried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)wikipedia answeredcarried from build of 2026-09-19; this build: skippedinat.taxon not askedinat.photos.wild answeredcarried from build of 2026-09-19; this build: skippedinat.photos.cultivated nothing to reportcarried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)commons nothing to reportcarried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)gbif.media answeredopenalex answeredcarried from build of 2026-09-19; this build: skippedEvery upstream is recorded as having answered, reported nothing, or refused. Only “nothing to report” is ever shown as an absence. Records came from 59 datasets via GBIF.org; each carries its own licence.








