Mikania micrantha

Name and classification

Mikania micrantha Kunth
Family Asteraceae, Tribe Eupatorieae

Common names

mile-a-minute, bittervine

Disseminule

fruit

Description

Fruit an achene, narrowly oblanceolate to narrowly oblong, sometimes slightly curved, 1.2–2(3) mm long, 0.2–0.6 mm in diameter, with 4–5 light-colored longitudinal ribs; cross section 4 or 5 sided. Surface blackish-brown, minutely granular, with few to many conspicuous drops of amber resin. Base narrows, then flares into a straw colored, irregularly cup shaped basal scar. Pappus persistent, one row of 32–38 ivory to light amber finely barbed bristles, 2–3 mm long. Style base inconspicuous. Apex horizontal, blackish-brown, granular. Embryo straight, spatulate; endosperm absent.

Identification considerations

Similar species

Ageratina adenophora (Sprengel) R. King & H. Robinson (=Eupatorium adenophorum Sprengel)

Ageratina riparia (Regel) R. King & H. Robinson

Mikania cordata (Burm. f.) Robinson

Mikania scandens (L.) Willd. (non-FNW)

Distribution

native to Central and South America, Mexico, and the West Indies

naturalized in India, Pakistan, Sri Lanka, Southeast Asia, the Pacific Islands, United States

Habitat

wet places, sometimes at high elevations, forest borders and clearings, along streams and rivers; a weed of pastures, tree crops, open disturbed areas, roadsides, waste places

General information

Mikania micrantha is a rapidly growing herbaceous to semi-woody, perennial vine. It grows quickly over other plants such as young trees, smothering them; it can climb trees up to 25 m tall. Although not as serious a weed as M. cordata, in Southeast Asia it has become a hard-to-eradicate weed of tea, rubber, and other plantation crops. It also reduces the carrying capacity of pasture. The achenes are spread by wind, water and animals. The plant also reproduces by old rootstocks, runners, and suckers.

achenes

achenes

achene, detail

achene, detail

A, achene; B, achene outline showing entire pappus; C, longitudinal section showing embryo; D, transection of achene; drawing by Lynda E. Chandler

A, achene; B, achene outline showing entire pappus; C, longitudinal section showing embryo; D, transection of achene; drawing by Lynda E. Chandler

apex of achene

apex of achene