Sadly, black taro and elephant ears are no good for eating.
While classified Colocasia esculenta, the same species as the edible variety, these ornamental plants do not produce the large underground corms that are eaten as a staple food in tropical countries all over the world.
Those nutritious starchy edible yams require leaching before consumption to remove high levels of oxalic acid, but this food source sustains millions around the planet. The leaves too, twice boiled, are tasty and nutritious in soups and other dishes.
The decorative varieties of this species, however, bred primarily for showy leaves, do not produce a burly edible tuber suitable to feed large families. These attractive plants put more effort into their foliage and reproduce vegetatively, rapidly and persistently. The oxalic acid levels contained in the plant tissues are also extremely high, and there are reports of itching tongue and discomfort after eating, even after copious boiling.
Black taro grows vigorously in the subtropics where there is plenty of moisture. It is popular in pond and pool landscaping. Creek banks and swampy regions are also a favoured habitat. When escaped into waterways, taro can choke the flow, form thick clumps and displace natives, both plants and wildlife due to its toxicity. Disrupting the progress of water, these plants collect silt in their roots, which become a stinky mess. Clumps of taro can break off during floods and spread downstream, establishing new infestations.
Wild taro can be a big problem. In South-east Qld, the Enoggera Creek catchment group, Save Our Waterways Now has prioritised this weed. They organise regular working bees to manage its impact. Black taro is a runaway in the Nimbin valley and other parts of the Northern Rivers, with several hotspots around. Some of these infestations are quite large.
Management of wild taro is not easy. Herbicides are not effective as the waxy cuticles of the leaves simply repel the liquid. (Glyphosate is now labelled a ‘probable carcinogen’ by WHO, so not recommended for use anywhere, let alone on a creek bank.)
Manual removal can be done when water levels are lower in the drier periods. Wear protective clothing as sap from this plant is very irritant. Take care in handling and try not to break the stems.
Wild taro is heavy, so team work is essential. Weeded material can be carried above the water line and covered with black plastic to cook and break down. Follow up is essential, as root fragments will regrow, but the job will get easier over time. Persistence pays off. Monitor carefully downstream and ensure new incursions are dealt with promptly before they establish in a big way.
Removal of taro should be done in conjunction with replanting the creek banks. Suitable species include sandpaper fig, lomandra, carex and lilly pilly to stabilise the disturbed soil.
Lesser known is Callisia repens aka turtle vine or creeping inch plant (lower pic) another species with potential to invade bushland. It forms dense mats which exclude other vegetation. Though small and delicate, it is exceptionally hardy. This innocuous looking creeper has been observed surviving weeks in a bucket on a veranda with no water, and still looks as fresh as the day it was removed from the garden. It has a remarkable potential to withstand drought or total neglect. And it thrives in the wild. You hardly notice it at first and then suddenly it’s everywhere.
Ensure garden waste is disposed of responsibly and not chucked down the gully or dumped by the roadside or in bushland. Alternative disposal methods include hot composting, weed tea, or feeding to worms.
The following notes to differentiate Black Taro from edible Taro are from Brisbane City Council’s ‘weed identification tool‘:
- Colocasia esculenta var. esculenta (cultivated and naturalised) has green or pruplish leaves and leaf stalks, and its corms are well developed (up to 30 cm long and 15 cm thick). Its flower clusters have a very short extension at the tip that is devoid of flowers (i.e. rudimentry appendix).
- Colocasia esculenta var. antiquorum (cultivated and widely naturalised) has green or pruplish leaves and leaf stalks, and its corms are relatively small (4-7 cm long and 2-5 cm thick). Its flower clusters have a relatively long extension at the tip that is devoid of flowers (i.e. well-developed appendix).