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Plantae / Angiospermae (Flowering plants) / Angiosperms (Seed Plants) / Gentianales / Dicot

Apocynaceae A.L. de Jussieu
Milkweed Family


The Apocynaceae are trees, shrubs or sometimes herbs, usually with milky sap comprising about 200 genera and 2,000 species. The leaves are simple, usually opposite and decussate, or whorled; stipules are usually absent. The flowers are bisexual and actinomorphic or sometimes weakly zygomorphic. The calyx is synsepalous and usually 5-lobed. The corolla is sympetalous and usually 5-lobed. The stamens are distinct, as many as corolla lobes and alternate with them, and adnate to the corolla tube (or perigynous zone). The anthers are introrse and commonly adherent to the surface of the stigma. The gynoecium consists of a single compound pistil of 2 carpels that may be distinct at the level of the superior or rarely partly inferior ovary but which are united by a single style. When distinct, each ovary typically has few to numerous ovules on marginal placentae; when connate, the placentation is axile or intruded parietal. A nectary consisting of 5 glands or an annular ring is usually found at the base of the ovary. The fruit is commonly a follicle, capsule, or berry. The seeds usually are flat and winged or have a tuft of hairs at one end.

Worldwide: 355 genera and 3700 species
Hawaiian Flora: 6 genera and 10 species
Widespread in tropical and subtropical, but with a few genera extending into temperate region.
Major Genera:
Asclepias (230), Tabernaemontana (230), Cynanchum (200) , Ceropegia (150), Hoya (150), Matelea (130), Rauvolfia (110), Gonolobus (100), Secamone (100) and Mandevilla (100).
Economic Use(s):
Nearly all taxa are poisonous and many have medicinal uses. Catharanthus provide antileukemia drugs, Rauvolfia provides a hypertensive drug, and Strophanthus provides a heart drug. Also ornamentals.
UH Manoa Campus Accession(s)

Lyon Arboretum Accession(s)

Key Characters  
Flower: Complete, Perfect .
Floral Symmetry:
+, Differentiated.
Tepals (T):
Calyx (K):
5, Coalescent, Hypogynous.
Corolla (C):
5, Coalescent, arising from Perigynous Zone (PZ).
Androecium (A):
5, Distinct, adnate to Perigynous Zone or to massive Stigma.
Gynoecium (G):
Syncarpous, Pistil=1, Carpels/pistil=2, Locules/pistil=2, Ovules/locule=2-?.
Superior to sometimes partly Inferior.
Axile or Parietal.
Follicles, Berry, or Drupe.
Opposite and Decussate or Whorled or rarely Alternate.
reduced or absent.
Other distinctive features:
Carpels generally distinct at level of ovary or even up to the single stigma; Sap Milky; Stamens commonly weakly coherent around generally enlarged Stigma or completely adnate to a massive Stigma; Pollen often in paired coherent masses (Pollinia); Corolla appendages or Corona (Crown) often present.
Floral Formula:

Profile Diagram of Flower Transverse Diagram of Flower
Web References: Angiosperm Phylogeny Website, Wikipedia

Angiosperm Phylogeny Group (2003). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141: 399-436 (Available online: Abstract | Full text (HTML) | Full text (PDF))

The Angiosperm Phylogeny Group. (1998) An Ordinal Classification for the Families of Flowering Plants. Annals of the Missouri Botanical Garden. [1]

Carr, Gerald. Vascular Plant Family Page.

Judd, W. S., C. S. Campbell, E. A. Kellogg, P. F. Stevens, & M. J. Donoghue. 2007. Plant Systematics: A Phylogenetic Approach, 3rd ed.

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Citation: Core Systematics Curriculum Module. University of Hawai'i at Manoa, Department of Botany. Honolulu, HI.
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