Opuntia humifusa

Opuntia humifusa
Opuntia humifusa

(Rafinesque) Rafinesque, Flora Medica (or Manual of the Medical Botany of the United States of North America) 2: 247, 1830

Neotype; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; HerbariumHerbarium (as O. calcicola); Herbarium (as Cactus humifusus); Herbarium (as Cactus opuntiaDrawing (Curtis’s Botanical Magazine, vol. 50: pl 2393, 1823 [as Cactus opuntia]); Drawing (Audubon, Birds of America [double elephant folio edition, plate 94, as Cactus opuntia] ca. 1830) 

See O. cespitosa  See O. lata  See O. mesacantha

What is Opuntia humifusa?

Opuntia humifusa is a distinct species though it has been lumped with other taxa. This prickly pear ranges from New England to Virginia (Georgia?).

Morphology

O. humifusa is difficult to differentiate in the field from O. mesacantha and O. lata. However, O. humifusa does not have spines, whereas the others often do. 

From The Flora of North America Online

  • Shrubs, forming clumps or often prostrate, usually only 1 or 2 stem segments tall, to 0.2 m  Stem segments not disarticulating, dark or bright shiny green, wrinkling when stressed, circular to broadly oblong to obovate, 5-17.5 × 4-12 cm, fleshy, usually tuberculate, glabrous; areoles 4-6 per diagonal row across midstem segment, oval to circular, 2-4 mm diam., not raised, sometimes somewhat sunken; wool tan to brown. Spines  absent. Glochids in dense crescent of adaxial edge of areole and in dense tuft overtopping crescent in age. Flowers: inner tepals pale to bright yellow throughout, 20-30 mm diam.; filaments yellow to orange; anthers pale yellow to cream; style and stigma lobes white. Fruits greenish, tardily becoming apricot to brownish red, elongate, 30-50 × 12-20 mm, fleshy, tapering at base; pulp green and sour. Seeds tan, 3.5-4.5 mm diam., thickish; girdle protruding to 1 mm.

NoteO. humifusa is spineless.  Flowers are yellow with no red.

Phylogeny

O. humifusa s.l. is a constellation of similar-appearing taxa–a collection of species that originated through hybridization. O. humifusa was unlumped from closely related prickly pears by Dr. Majure who showed that the one species (O. humifusa) was in fact a complex of four related taxa (O. humifusaO. cespitosa, O. lata, and O.  mesacantha). There are several relevant publications by Dr. Majure (Cytogeography, Mississippi, Ecology, Taxonomic Revision, and Evolution) that provide new information about these related Opuntia species.

Ecology, etc

O. humifusa is not a desert plant. Rather, it is often an opportunistic cactus in areas that receive heavy rainfall or runoff part of the year but which are hot and dry other parts of the year. Hence, it is often found growing on rocky outcrops. 

Read the original citation. Opuntia humifusa is tetraploid, but diploid populations are reported.  

O. humifusa is a long-time garden favorite. It is easy to grow, tolerant of rain and snow, the right size for most gardens, and a cheerful bloomer. 

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