Gonolobus suberosus (L.) R. Br.


Gonolobus suberosus plant

Family - Asclepiadaceae

Stems - Herbaceous, vining, twining, terete, with milky sap, multiple from the base, to many meters long, pubescent with long multicellular hairs and short glandular hairs. Some hairs with pustulate bases.

Gonolobus suberosus stem

Leaves - Opposite, petiolate. Petioles to +/-10cm long, less pubescent than the stem, terete. Blades ovate, cordate, acute, entire, to +/-20cm long, +/-10cm broad, densely glandular pubescent below (the hairs with the gland below the apex and with a sharp tip), less pubescent adaxially, dull green adaxially, light green abaxially.

Gonolobus suberosus leaves

Inflorescence - Axillary umbellate clusters of 2-10 flowers. Pedicels sparsely short pubescent with the same hairs as the leaves, to 1.5cm long. Pedicels with small subulate bracts at the base (1 per pedicel). Bracts to 1.5cm long, .3mm broad, ciliate-margined.

Gonolobus suberosus inflorescence

Flowers - Petals 5, united at the base, spreading, -1cm long, +/-3mm broad at the base, narrowly triangular, entire, olive-green, with a thin light margin, glabrous. Column short (1-1.5mm tall), +/-3mm broad (diameter), green at the apex, subtended by a large yellowish nectary. Pollinia -1mm long (total). Terminator purplish. Pollen sacs greenish (olive). Pistils 2, glabrous, with vertical ribs, 2mm long in flower. Sepals 5, green, subulate-ovate, to +/-3mm long, 2mm broad, glabrous, entire, with the apices recurved. Sometimes the sepals with short cilia at the apex.

Gonolobus suberosus calyxCalyx.

Gonolobus suberosus flowerFlower close-up.

Flowering - July - August.

Habitat - Rocky woods, thickets.

Origin - Native to U.S.

Other info. - This interesting milkweed sibling can be found only in extreme southern Missouri and only in a handful of counties. The plant is not rare, it just reaches the northern edge of its range in Missouri.
G. suberosus is easy to identify in the field because of its big cordate leaves, vining habit, and greenish star-shaped flowers.
The species has been called Matelea gonocarpa. The flowers resemble those in the Matelea genus.

Photographs taken in the Ozark National Scenic Riverways, Carter County, MO., 7-15-03.