Colocasia esculenta (L.) Schott

Rhizome vertical to horizontal, tuberous, 3-5 cm or more (up to 15 cm) in diam. Stolons long or absent. Leaves 2 or 3 or more; petiole green, 25-80 cm, sheathing for 1/3-2/3 length; leaf blade adaxially matte waxy-glaucous and water-shedding (water sometimes forming "mercury droplets"), oblong-ovate to suborbicular, 13-45 × 10-35 cm, base shallowly cordate (sinus 1-4 cm), apex broadly and shortly cuspidate. Peduncle usually solitary, 16-26 cm. Spathe tube green, 3.5-5 × 1.2-1.5 cm; limb open proximally, cream-colored to golden yellow, lanceolate or elliptic, 10-19 × 2-5 cm, apex acuminate. Spadix: female zone conic, 3-3.5 × ca. 1.2 cm; ovary 1-3 mm in diam.; stigma subsessile, narrower than apex of ovary; sterile zone narrowly cylindric, 3-3.3 cm; sterile flowers (pistils) seen from above elongate, ca. 0.5 mm in diam.; male zone cylindric, 4-6.5 cm × ca. 7 mm; appendix narrowly conic, 15-45 × ca. 2 mm. Berry green, ca. 4 mm. Seeds few; synandria ca. 1 mm high, ca. 0.8 mm in diam. Fl. Feb-Apr (Yunnan), or Aug-Sep (Qin Ling area). 2n = 26, 28, 30, 36, 38, 42, 44, 46, 48, 52, 58, 84, 116.

In northern Australia, grows in open areas with permanent fresh water: creeks, billabongs, swamps and splash-zone of waterfalls, at low to moderate elevation (to 1700 m in Java). In the Kimberley it occurs partially submerged in, or at the edge, of watercourses (Rye 1992: 982). Naturalised in disturbed areas, drains, watercourses.

The corms, petioles and leaves are all edible after cooking. The leaves are also dried and stored. The leaves are used for sarma in Turkey. They are rolled around a filling of rice or minced meat. The flowers are also cooked as a vegetable. CAUTION Some varieties burn the throat due to oxalate crystals. To remove these soak in baking soda for 2 hours then boiled for 60 minutes. Tamarind is used for this purpose in India. Fresh leaves can be stored for 4-5 days. Leaves and stalks can be dried and stored.

Taro can be planted from cormels or from the top of the central corm. Other sections of the corm could also be used but this is not commonly done. Flowering of taro and seed production can lead to new cultivars. Flowering can be promoted by the use of gibberellic acid. The general growth pattern is for an increase in top growth, in terms of leaf number, leaf area and petiole length, to continue for about 6 months under tropical lowland conditions then for each of these to decrease and tuber storage to continue to increase. Corm weight increases significantly from 5 to 11 months. Starch content also increases with time but protein content declines over the corm development period. Taro can be grown under flooded conditions but root rots develop if the water becomes stagnant. For flooded cultivation, the land is cleared, ploughed, cultivated and puddled. The aim is to get a field that is flat with embankments allowing the impounding of water. Planting is done into 2-5 cm of standing water. For dryland taro, the soil is prepared by digging, unless a fresh bush fallow is used where the natural friability of the soil allows plants to be put into the undug soil in a small hole that is prepared. Plants are put into a hole 5-7 cm deep or deeper. Mulching to conserve moisture and reduce weed growth in beneficial. Setts from corms normally give higher yield than that from cormels. The greater leaf area and root production may be responsible for this. Setts of about 150 g are optimum. The time of planting is primarily determined by the availability of moisture. Planting is done shortly after the rainfall has become regular, if seasonally distinct wet and dry seasons occur. Higher rainfall, higher temperatures, and higher hours of sunlight, enhance production and determine seasonality of production. Evapotranspiration for flooded taro averages about 4 mm per day, ranging from 1.5 to 7.2 mm, with a total of about 1200 mm for the crop. Intermittent moisture can result in irregular shaped corms. Flooding has been found to be more effective than sprinkler irrigation, or furrow irrigation. Increased suckering, giving greater leaf area, seems to be the reason for this. Taro is sensitive to weed competition throughout most of its growth, but it is more critical during early growth up to 3-4 months. About 7-9 weedings are required, to keep the crop clean under tropical lowland conditions, where flooding is not used. Due to the decrease in height and leaf area towards the end of the growth cycle when starch accumulation in the corms is maximum, weed competition and weed control are again significant. Mechanical weeding needs to be shallow to avoid damaging the superficial taro roots. A range of herbicides have been recommended in various situations. Taro produces the highest dry matter yield under full sunlight, but it can still grow under moderate shade. Under shaded conditions it grows more slowly and develops less cormels. They require good moisture conditions and have little tolerance for drought. Taro residue has an allelopathic factor which can reduce the germination and growth of other plants, for example, beans. Taro tends to demand high fertility, and is responsive to additional NPK fertiliser. Higher doses of K increases starch content and higher doses of N increases protein content. Both N and K applications increase oxalic acid content of the tubers. Spacing affects total yield, and marketable, harvestable yield, of corms. Close spacing increases the corm yield per area, and the shoot yield per area, but decreases the corm yield per plant, and the contribution of sucker corms, to the yield. Where spacings of 30 cm x 30 cm are used, giving about 110,000 plants per hectare, a very large amount of planting material is required, which reduces the net return per unit of planting material. A spacing of 60 cm x 60 cm in more common. Wider spacings of 90 cm x 90 cm reduces overall yield.