mikania

Mikania micrantha
Vine
Opposite
Simple
White
Green

A long-lived vine with slender ribbed stems and oppositely arranged leaves. Its leaves are heart-shaped or somewhat triangular, hairless, and have coarsely toothed margins. Numerous fluffy white flower-heads are borne in branched clusters in the leaf forks or at the tips of the branches. The tiny black seeds (1.5-2 mm long) are topped with numerous whitish coloured hairs or bristles (2-4 mm long).

Common names 
Also known as: mikania vine, American rope, bitter vine, climbing hemp, climbing hempweed, mikania, mile-a-minute,
Family 
Asteraceae
Deciduous 
No
Flowering time 
Year Round
Native/Exotic 
Exotic
Origin 
Native to Mexico, Central America, the Caribbean and tropical South America.
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

This species is not yet widely naturalised in Australia. It has only been recorded from a few locations in the coastal areas of northern Queensland (e.g. Speewah, Mission Beach, Ingham and Kuranda) and on Christmas Island. Also naturalised in tropical Asia (e.g. India, Nepal, Bangladesh, Sri Lanka, China, Indonesia, Malaysia, Brunei, the Philippines, Singapore, Thailand and Papua New Guinea), the Mascarenes (e.g. Mauritius), Melanesia, Polynesia and Hawaii.

Habitat 

A potential weed of wetter habitats in the tropical and sub-tropical regions of Australia. This species invades disturbed forests, forest margins, waterways, roadsides, pastures, plantations and some crops.

Habit 

A fast-growing, much-branched, and long-lived (i.e. perennial) vine with a climbing, twining or creeping habit. Its stems can grow up to 6 m or more long.

Impact and control methods 

Mikania vine (Mikania micrantha) is regarded as a potentially significant environmental weed in northern Queensland, and in other parts of northern Australia. It was recently listed as a priority environmental weed in at least one Natural Resource Management region and appears on the Northern Australia Quarantine Strategy (NAQS) list.Becuase of its invasiveness in other parts of the world, mikania vine (Mikania micrantha) is also listed in the Global Invasive Species Database, and is regarded to be in the top 100 of the world's worst invasive alien species.

Stem and leaves 

The slender stems are ribbed lengthwise (i.e. longitudinally) and are either hairless (i.e. glabrous) or slightly hairy (i.e. puberulent). These stems sometimes produce roots (i.e. adventitious roots) at their joints (i.e. nodes). The leaves are oppositely arranged (4-13 cm long and 2-9 cm wide) and either heart-shaped (i.e. cordate) or somewhat triangular in shape with a long pointed tip (i.e. acuminate apex). These leaves are borne on stalks (i.e. petioles) 2-8 cm long, are hairless (i.e. glabrous), and have coarsely toothed (i.e. dentate or crenate) margins.

Flowers and fruits 

Numerous fluffy flower-heads (i.e. capitula) are borne in branched clusters originating in the forks of the leaves or forming at the tips of the branches (i.e. in axillary or terminal corymbs). These flower-heads (i.e. capitula) are small (3-6 mm long) and white or greenish-white in colour. They do not have any obvious petals (i.e. they have no ray florets) and consist of four tiny flowers (i.e. tubular florets), each 3-4 mm long, surrounded by a row of four small green bracts (i.e. involucre). These bracts (2-4 mm long) are oblong to egg-shaped in outline (i.e. obovate) with pointed tips (i.e. acute apices). Flowering occurs mostly from late autumn through to early spring. The tiny black or blackish-brown 'seeds' (i.e. achenes) are elongated (i.e. linear-oblong) in shape and five-angled in cross-section. These seeds (1.2-2 mm long and 0.2-0.6 mm wide) are topped with a ring (i.e. pappus) of numerous (30-38) whitish coloured hairs or bristles (2-4 mm long).

Reproduction and dispersal 

This species reproduces by seeds and also vegetatively via stem fragments that can readily develop into new plants.The seeds are generally spread by wind, or become attached to animals and clothing. Stem fragments can be dispersed to new areas in dumped garden waste, during cultivation practices, and during floods.

Similar species 

Mikania vine (Mikania micrantha) is reasonably similar to several other vines including the climbing groundsels (Senecio angulatus and Senecio tamoides) and ivy groundsel (Delairea odorata) when not in flower. However, these species all have yellow flowers and are usually only found in sub-tropical and temperate regions.It is also reasonably similar to the native headache vine (Clematis glycinoides), but on close inspection this species has leaves with three leaflets (i.e. trifoliate leaves) and its flowers have four petals.