Plant of the Week
Baldwyn's Milkvine (Matelea baldwyniana)
By Dave Moore
Baldwin’s milkvine is a perennial, herbaceous, vining member of the Milkweed (Asclepiadaceae) family. It is easily recognizable due to its paired, opposite, white flowers with twisted petals (most species of Matelea have maroon or burgundy flowers), and heart-shaped leaves. Its common name is in reference to William Baldwin (1779-1819), a physician and one of the first botanists to explore the American Southeast, especially Georgia and Florida, as well as parts of Latin America and the West Indies.
Baldwin’s milkvine occurs in seven states, principally in the Southeastern United States but also Missouri and Oklahoma, where it can be found growing in limestone and dolomite glades, and dry, rocky, open woods on calcareous substrates.
According to the Plants National Database, there are 31 species of Matelea in the United States, and each of these is a native plant. The genus Matelea is native only to the Western Hemisphere, where about 200-250 species occur in the United States, Mexico, Central and South America, and the Caribbean Islands. Due principally to slight differences in the flowers and fruits, current taxonomical work has broken out some species of Matelea and placed them in the genus Gonolobus.
The flowers of the Asclepiadaceae are complex and include specialized structures. These structures promote out crossing by various insect pollinators. A specialized terminology has developed to account for these unusual floral structures. The complex of carpels, stamens, and coronas is collectively termed the gynostegium. An elaborate, acellular, wishbone-shaped complex consisting of two threadlike arms, called translators, and a central, longitudinally grooved, disc like structure called the corpusculum, connects the pollinia from adjacent anthers. The complex of two pollinia along with the translator apparatus is technically known as a pollinarium, but in practice, many botanists continue to refer merely to pollinia in discussing the pollen transfer of asclepiad flowers (Yatskievych 2006).