Opuntia polyacantha

Family

Cactaceae

Subfamily

Opuntioideae

Genus according to POWO

Opuntia

Growth form

Low, extensive clumps of flattened stem segments

Rozmieszczenie

POWO gives the range as central Canada to west-central and central United States. It includes Alberta and Saskatchewan and a broad belt from Idaho and Nevada to the Dakotas, Kansas, Oklahoma and Texas. The database recognizes two botanical varieties, emphasizing variation within the species. [2-WWW]

A species name without a variety and location covers material from very different latitudes and elevations. For overwintering assessment, provenance is more valuable than a general statement of occurrence in Canada. [2-WWW]

Siedlisko

It grows in open prairies, dry grasslands, plains, gravel terraces and rocky slopes. In parts of its range, it occurs with steppe vegetation and sagebrush scrub. Strong light and limited competition are common features of many sites, but substrate texture and chemistry vary. [4-WWW] [2-WWW]

Excess precipitation during Poland's cold season has no simple equivalent in the continental climate of parts of the range. Information on native habitat helps design drainage but does not replace a local trial. [4-WWW] [2-WWW]

Budowa

Flattened segments form low branched clusters. Areoles have glochids and spines whose number, length and arrangement differ markedly between populations. Flowers may have different shades of yellow and pink. Colour alone is insufficient for identification. [4-WWW] [2-WWW]

Horizontal growth allows the plant to occupy an area without building a tall framework. Segments nevertheless retain polarity and defined sites for development of new shoots and flowers. [4-WWW] [2-WWW]

Biology

The species reproduces sexually and vegetatively. Clump expansion and rooting of fragments maintain one genotype at a site, while sexually produced offspring introduce new allele combinations. When assessing a collection, several segments obtained from one plant should be treated as a clone. [4-WWW] [2-WWW]

The broad range favours local variation in seasonal traits. A commercial label does not indicate whether material comes from a northern prairie, a southern plateau or old cultivation without field data. [4-WWW] [2-WWW]

Identification and documentation

For identification, document the habit of the whole clump, mature segment shape, spine arrangement and floral characters. Because POWO recognizes botanical varieties, a species-level name may be correct yet insufficient for comparing two distant populations. [4-WWW] [2-WWW]

A clone number should remain linked to every cutting. After several years, material is easily confused when all plants bear only the species name. Do not combine observations from different clones into one temperature record. Differences may reflect provenance, age, rooting or micro-site. [4-WWW] [2-WWW]

Physiology of frost hardiness and scope of the data

Ishikawa and Gusta studied winter material from near Pike Lake in Saskatchewan. With at least five detached segments per temperature and three controlled-freezing replicates, LT₀ was −40°C, and LT₅₀ assessed from tissue damage was −55°C. Ice was initiated for 12 hours at −3,5°C, after which material was gradually cooled. Necrosis was assessed after four weeks, and regenerative ability was also checked later. [Ishikawa and Gusta 1996]

In Nobel's comparison, material from southeastern Wyoming at 2230 m elevation, after 4–6 weeks at 10/0°C, had a temperature for halving cellular staining of −17,1 ± 0,7°C. The mean and standard deviation concerned six stems cooled at about 2°C per hour. The discrepancy with the Canadian result includes provenance, preparation and method, so it does not justify selecting one universal boundary for the species. [Nobel 1982] [Ishikawa and Gusta 1996]

Notes on sources

Measurements are available for particular provenances. Winter segments from Saskatchewan reached LT₀ −40°C, while Wyoming material examined by another method had a threshold for halving cellular staining of about −17,1°C. Protocols and assessment criteria differ. [Ishikawa and Gusta 1996] [Nobel 1982]

Experiments described in the literature

Source material

Species record in Plants of the World Online [2-WWW] [4-WWW] [2-WWW] [Ishikawa and Gusta 1996] [Nobel 1982]

Dokumentacja ogrodnicza CSU Extension

The name and range were checked in POWO on 8.10.2026. The profile distinguishes source data from cultivation inferences.