ASCLEPIADACEAE

MILKWEED FAMILY

Carol A. Hoffman

Annual, perennial herb, shrub, vine; sap milky
Leaves simple, generally opposite or whorled; stipules 0 or small
Inflorescence: cyme, terminal or axillary, umbel- or raceme-like, or flower solitary
Flower bisexual, radial; sepals 5, generally reflexed; petals 5, generally reflexed or spreading; stamens 5, fused to form filament column and anther head, generally with 5 elaborate appendages on outside of filament column, pollen removed in pairs of massive sacs; ovaries 2, superior, free, style tips generally fused into massive pistil head surrounded by anther head
Fruit: follicle (1 ovary generally aborts)
Seeds many, ± flat, with tuft of silky hairs
Genera in family: 50–250 genera, 2000–3000 species: especially tropical, subtropical South America, s Africa; ornamental (Asclepias, Hoya, Stapelia). Cardiac glycosides produced by some; used as arrow poisons, in medicine to control heart contraction, and by some insects for defense
Recent taxonomic note: Recently treated to be included within Apocynaceae

ASCLEPIAS

MILKWEED

Annual, perennial herb, shrub
Stem prostrate to erect
Leaves alternate, opposite, or whorled; blade narrowly linear to ovate or cordate
Inflorescence: umbel-like, generally terminal and in (especially upper) axils
Flower: ring of tissue at base of corolla 0; filament-column appendages (hoods) free, sometimes elevated above corolla base, each often with an elongate projection (horn) attached to inside, solid, margins curved in and meeting or nearly meeting on side adjacent to column but not fused; top of pistil head flat or conic
Fruit generally erect (pedicel generally pendent), narrowly ovoid, smooth or with tubercles
Species in genus: 100 species: Am
Etymology: (Asklepios, ancient Greek physician)
Reference: [Woodson 1954 Ann Missouri Bot Gard 41:1–211]

Native

A. cryptoceras S. Watson

HUMBOLDT MOUNTAINS MILKWEED

Perennial, ± glabrous
Stem prostrate to decumbent
Leaves opposite, persistent, sometimes sessile; blade ovate to nearly round, sometimes cordate, base rarely clasping stem
Inflorescence generally terminal
Flower: corolla reflexed, greenish yellow; hoods not elevated above corolla base, ± = anther head, pinkish tan; horns 0 or included in hoods
Fruit: pedicel erect
Ecology: Sandy or gravelly slopes, canyon bottoms, arid plains
Elevation: 1400–1700 m.
Bioregional distribution: East of Sierra Nevada (Mono Co.)
Distribution outside California: to Washington, Wyoming, Colorado, Arizona
Flowering time: May–Jun
If the dubious subspp. are recognized, CA plants (with hoods slightly < anther head) are subsp. davisii (Woodson) Woodson. Ssp. cryptoceras (hoods generally slightly > anther head) has been reported from SNE (Mono Co.), is listed as UNCOMMON. Even if recognized, its occurrence in CA must be doubted
Horticultural information: TRY.