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Lycium exsertum; photograph (c) CK2AZ, some rights reserved (CC BY) CC BY(c) CK2AZ, some rights reserved (CC BY) · observed growing wild · 2026-08-12

Lycium exsertum A.Gray

Arizona desert-thorn

Solanaceae · Arizona, Mexico Northwest

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Lycium exsertum, photograph (c) Matt Berger, some rights reserved (CC BY)Lycium exsertum, photograph (c) Matt Berger, some rights reserved (CC BY)Lycium exsertum, photograph (c) Matt Berger, some rights reserved (CC BY)Lycium exsertum, photograph (c) Matt Berger, some rights reserved (CC BY)Lycium exsertum, photograph (c) CK2AZ, some rights reserved (CC BY)Lycium exsertum, photograph (c) CK2AZ, some rights reserved (CC BY) 89 photographs ›
Habitat figures
Cold floor (1 night in 100)
-1.9°C
Record low -11.9 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
38°C
Jul at the habitat CHELSA
Rain a year (median across the range)
318mm
7 months of 25 mm or more in the median year CHELSA
Open-sky light
20–54DLI
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 December to March and July to September, read as a winter growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Lycium exsertum, the Arizona desert-thorn, is a species of flowering plant in the family Solanaceae. It is native to southern Arizona and northwestern Mexico. A large shrub reaching 12 ft (3.7 m), it is typically found in deserts and scrublands on slopes and alluvial washes.

Quoted from Wikipedia, "Lycium exsertum", CC BY-SA 4.0.

About the genus · Lycium

Lycium is a genus of flowering plants in the nightshade family, Solanaceae. The genus has a disjunct distribution around the globe, with species occurring on most continents in temperate and subtropical regions. South America has the most species, followed by North America and southern Africa. More on Wikipedia ›

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

Cultivation

Seasons

The rain rule reads a winter growing season: 70% of the median year's rain (239 mm of 302 mm) falls in December to March and July to September, cooler than the year (wet-season mean 19.6 °C against a yearly mean of 20.7 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: January to March and June to September.

Rain

302 mm in the median year at the habitat, 239 mm of it December to March and July to September. Wettest month August at 48 mm, driest month June at 3 mm; 1 month under 5 mm. Across the grid cells of the range the year's total runs 213 mm to 451 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 318 mm, is the year's rain at the top of the page; the 302 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: 20 to 54 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 19, the highest 90th-percentile month 54).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -1.9 °C, the absolute minimum -11.9 °C, 513 frost nights in 44 years, 11.7 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 43.1 °C. Monthly means: the coldest month's mean nightly low 4.0 °C in January and December (across the grid cells of the range 1.5 °C to 7.0 °C), the warmest month's mean daily high 37.5 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -1.9 °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: 34 to 49% 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 -184 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 Lycium exsertum through the yearWarmest month July, mean daily high 38 °C; coldest months January and December, mean nightly low 4.0 °C; 302 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.-20°-10°0°10°20°30°40°50°frost43.1° 99th-percentile day, NASA POWER-11.9° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100mm rainDLI 20–54RH 34–49%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 265 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 °C17 / 15–1919 / 16–2122 / 19–2527 / 24–2932 / 28–3437 / 33–3938 / 33–4036 / 32–3934 / 30–3728 / 25–3122 / 19–2417 / 14–19
Night °C4 / 2–75 / 3–88 / 5–1111 / 9–1417 / 13–1922 / 18–2425 / 21–2724 / 20–2721 / 18–2315 / 12–178 / 6–114 / 2–7
Rain mm33 / 21–4634 / 21–4530 / 18–4511 / 5–165 / 2–93 / 1–933 / 21–8048 / 32–8128 / 18–4822 / 15–3022 / 12–3033 / 22–44
DLI22 / 21–2528 / 27–3138 / 37–4047 / 46–4852 / 52–5354 / 53–5448 / 46–4943 / 42–4439 / 38–4032 / 31–3424 / 23–2720 / 19–23
RH %49 / 46–5248 / 45–5044 / 41–4939 / 37–4336 / 34–4134 / 32–3943 / 40–4846 / 43–5144 / 41–4843 / 41–4745 / 42–4849 / 46–52
How this section is made
Each figure is the median across the 265 grid cells holding the 723 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 1133:1375 (33.325, -111.225). Over 44 years there: absolute minimum -11.9 °C, 1st-percentile night -1.9 °C, 99th-percentile day 43.1 °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 265 distinct grid cells holding 723 of the 723 in-range records; extremes and elevation at the typical cell 1133:1375 (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 33.50_-111.250, lapse-corrected -184 m at 6.5 °C/km. Elevation: ETOPO 2022, 737 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.
NativeArizona, Mexico 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 marker33.652, -111.749 · in the densest population, 763 records (86% of those in range)
Kew's description“shrub” · “desert or dry shrubland” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 885 georeferenced records inside the native range; the climate across the range on the 723 of them placed to within 10 km; the map shows only the 256 openly licensed ones, which alone would put the marker 16 km away. 162 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 885 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Lycium exsertum, photograph 1did not loadLycium exsertum, photograph 2did not loadLycium exsertum, photograph 3did not loadLycium exsertum, photograph 4did not loadLycium exsertum, photograph 5did not loadLycium exsertum, photograph 6did not load

Photographs: (c) Matt Berger, some rights reserved (CC BY) (4); (c) CK2AZ, 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.

Selaginella arizonica Selaginella arizonica Arizona spikemoss Photo: CC BY, Rachel StringhamCochemiea grahamii Cochemiea grahamii Graham's nipple cactus Photo: CC BY, Bruce HartmanSenna covesii Senna covesii Coues' senna Photo: CC BY, Rachel StringhamEphedra fasciculata Ephedra fasciculata Arizona Joint-fir Photo: CC0, author not statedCarnegiea gigantea Carnegiea gigantea Saguaro Photo: CC BY, Harrison J ElkinsCylindropuntia × tetracantha Cylindropuntia × tetracantha Cactaceae Photo: CC BY, Tom Field

Other Lycium 26 in the reference

Lycium afrum Lycium afrum Kaffir boxthorn Photo: CC BY, De Waal HugoLycium andersonii Lycium andersonii Water-jacket Photo: CC BY, Sue CarnahanLycium barbarum Lycium barbarum Duke of Argyll's teaplant Photo: CC BY, agujaceratopsLycium berlandieri Lycium berlandieri Berlandier wolfberry Photo: CC BY, Rachel Stringham Lycium boerhaviifolium Solanaceae Lycium brevipes Lycium brevipes Baja desert-thorn Photo: CC BY, Marc Fradera-SolerLycium californicum Lycium californicum California boxthorn Photo: CC BY, Konshau DumanLycium carolinianum Lycium carolinianum Christmasberry Photo: CC BY, Kristály Cravens-LiszakLycium cestroides Lycium cestroides Herzog cestrum Photo: CC BY, RAPLycium chilense Lycium chilense Solanaceae Photo: CC BY, Víctor Sarabia SánchezLycium chinense Lycium chinense Chinese teaplant Photo: CC BY, Hibiki KatayamaLycium ciliatum Lycium ciliatum Solanaceae Photo: CC BY, Marcos Gramaglia all 27 ›

Names & registers

Also known as Lycium fremontii var. bigelovii; Lycium retusum. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Solanaceae
Described by
A.Gray
Native to
Arizona, Mexico Northwest
Wild records
885 in range · 256 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; 27 records within 1 km of a botanic garden, herbarium or zoo left out (25 at a botanic garden or arboretum, 1 at a herbarium, 1 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 33.50_-111.250, lapse-corrected -184 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 36 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…