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. fascicularis Decne.

NARROW-LEAF MILKWEED

Perennial, generally glabrous
Stem ascending to erect
Leaves in whorl of 3–5, often with axillary clusters of small leaves, persistent; petiole short; blade narrowly lanceolate, base tapered
Flower: corolla reflexed, greenish white, sometimes tinged purple; hoods elevated above corolla base, generally < anther head, greenish white; horns generally > hoods (and anther head)
Fruit: pedicel erect
Ecology: Dry ground, valleys, foothills
Elevation: 50–2200 m.
Bioregional distribution: California (except North Coast, Central Coast, South Coast)
Distribution outside California: to Washington, Utah, Baja California
Flowering time: Jun–Sep
[not A. mexicana Cav.]
Horticultural information: DRN, DRY, SUN: 3, 7, 8, 9, 10, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24.