APOCYNACEAE

DOGBANE FAMILY

Lauramay T. Dempster

Perennial (sometimes annual, shrub, vine, tree); sap milky
Leaves simple, entire, opposite, alternate, or subwhorled; stipules 0 or small
Inflorescence: cyme; flowers 1–many, axillary or terminal
Flower bisexual, radial; perianth parts overlapping, at least in bud; sepals 5, fused at base, persistent; petals 5, fused in ± basal half; stamens 5, attached to corolla tube or throat, alternate lobes; ovaries 2, ± superior, generally free, styles and stigmas fused
Fruit: generally 2 follicles
Seeds many, often with tuft of silky hairs
Genera in family: ± 150–200 genera, 1000–2000 species: especially tropical; many ornamental (Nerium, oleander; Plumeria , frangipani); some alkaloids highly toxic, some used in medicine
Recent taxonomic note: Recently treated to include Asclepiadaceae
Reference: [Rosatti 1989 J Arnold Arbor 70:307–401]

AMSONIA

Plant erect
Stem ± woody
Leaves alternate to subwhorled
Inflorescence: flowers several–many
Flower: corolla salverform; anthers free from each other and stigma; nectary 0 or low ring around ovaries; style ± thread-like, stigma skirted at base
Seed glabrous
Species in genus: 5–25 species: North America, Japan
Etymology: (Probably for Charles Amson, Virginian physician, 18th century)
Reference: [McLaughlin 1982 Ann Missouri Bot Gard 69:336–350]

Native

A. tomentosa Torr. & Frémont

Plant glabrous or grayish tomentose
Stems several–many from woody crown, 16–36 cm
Leaf 2–4 cm; petiole short or 0; blade ovate-lanceolate
Flower: calyx lobes erect, thread-like above base; corolla whitish, blue, or greenish, tube ± 15 mm, inflated above middle, narrower just below spreading lobes; style spheric just below stigma
Fruit 3–8 cm, narrowed between seeds, often breaking into 1-seeded segments
Ecology: Desert plains, canyons
Elevation: 300–1800 m.
Bioregional distribution: San Bernardino Mountains (n slope), s Desert Mountains, Sonoran Desert
Distribution outside California: to Utah
Flowering time: Mar–May
Synonyms: A. brevifolia A. Gray
Hairiness is probably a simple, genetically recessive trait
Horticultural information: TRY.