Dioscorea bulbifera  L. 1753

pronounced: dy-oh-SKOR-ee-uh bulb-IH-fer-uh

(Dioscoreaceae – the yam family)

common name:  Air Potato

dioscorea bulbiferaair potato vine dioscorea bulbiferaleaves Dioscorea was named for Pedanius Dioscorides,  (c.40 AD—c.90 AD), Greek physician and pharmacologist,  whose work De materia medica was the foremost classical source of modern botanical terminology and the leading pharmacological text for 16 centuries. Bulbifera is botanical Latin for ‘bearing bulbs’ – fero, to bear.

The plant is found naturally in much of Asia and Africa, and is now spread to most tropical and sub-tropical areas, especially to Florida, where it is a major noxious weed. The plant photographed is in the Gustav Creek area of Nelly Bay. The air potato is an invasive vine, vigorously twining and long-stemmed, which may arise from an underground tuber, although these are often absent or inconspicuous. The stems are round or slightly angled in cross-section, and twine anticlockwise. They can reach 20 m in length, and grow as much as 20 cm per day in warm weather. Conspicuous aerial tubers, known as bulbils, are formed in the leaf axils, and are pale, up to 13 cm wide, and globose in shape.

dioscorea bulbiferaleaves & bulbil dioscorea bulbiferabulbilThe attractive leaves are alternate, broadly cordate, up to 20 cm long with long petioles. They are divided longitudinally into lobes by prominent veins. These all radiate out from a single point of origin, where the petiole is attached to the leaf.

The plant is dioecious, although flowering is uncommon in many parts of the world, and the chief means of reproduction is asexual, consisting of vegetative growth from underground tubers and above-ground bulbils. These generally sprout in the spring (or, in tropical Queensland, at the beginning of the wet season), and the new shoots often climb the dead stems from the previous year to reach the tree canopy.  By the time seasonal stem die-back occurs, a single vine may have put out as many as 200 bulbils. The bulbils can last a year or more on the ground and still be capable of sprouting, and soil contact is not necessary for sprouting. They also float, and are dispersed by flood waters.

Where flowers are produced, they are inconspicuous, greenish and fragrant, arising from leaf axils in panicles up to 10 cm long. Pollination is done by insects. The fruit is a capsule; the seeds are partially winged, and are dispersed by the wind. Seeds of the air potato, and other members of the genus, are believed to undergo an obligatory dormancy period of several months before they germinate. This may well be an evolutionary adaptation to make sure that viable seeds are present in the seed bank when breaks occur in the forest canopy.

In West Africa air potatoes are cultivated for their underground tubers, which can reach a couple of kilogrammes in weight; they are potato-like in flavour, and palatable.

Lepidoptera whose caterpillars use this as a food plant include the Yam Hawk Moth Theretra nessus and the Cacao Armyworm Tiracola plagiata.


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 Photographs aken in Nelly Bay 2013

Page last updated 18th March 2018

 

 

 

 

 

 

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