taro

Colocasia esculenta
Aquatic
Alternate
Simple
Green
Yellow
Green

A large herbaceous plant growing up to 1 m or more tall that produces tuberous creeping stems. Its very large leaves (17-70 cm long) are heart-shaped and borne on thick, spongy, stalks 30-100 cm long. These upright leaf stalks are joined to the undersides of leaf blades and are usually purplish in naturalised plants. Its elongated flower clusters (6-21 cm long) have green female flowers at the base and yellowish male flowers towards the tip. These clusters are mostly enclosed by a large greenish-yellow or yellow bract 20-35 cm long. Its fruit are small oval berries (3-5 mm long) that turn orange or red as they mature.

Common names 
Also known as: coco yam, cocoyam, dasheen, eddo, elephant ears, elephant's ear, taro, wild taro,
Family 
Araceae
Deciduous 
No
Flowering time 
Spring - Late Summer
Native/Exotic 
Native
Origin 
Probably originated in tropical Asia, now widely cultivated and naturalised in the tropical regions of the world. One wild variety (i.e. Colocasia esculenta var. aquatilis), that has poorly developed tubers, is thought to be native to some parts of northe
Notifiable 
No
Council declaration 
Class R – Reduce populations
Known distribution 

Naturalised in northern and south-eastern Queensland, in south-western Western Australia, and in the coastal districts of central and northern New South Wales.

Habitat 

A weed of waterways, riparian vegetation, wetlands and the margins of waterbodies.

Habit 

A large herbaceous plant growing up to 1 m or more tall.

Impact and control methods 

"Taro (Colocasia esculenta) is regarded as an environmental weed in Queensland, New South Wales and south-western Western Australia. This species is of particular concern in south-eastern Queensland and was recently ranked among the 200 most invasive plants in the region. It has spread from cultivation as a garden ornamental and invaded waterways and wetlands, where it forms large and dense colonies and replaces native aquatic plants.

It is also a problem in the coastal districts of New South Wales, north from Wyong, and is increasingly becoming a cause for concern along the waterways of the Swan and Moore River catchments in south-western Western Australia."

Stem and leaves 

"It produces tuberous creeping stems (i.e. rhizomes) that are either underground or slightly exposed above the soil surface.

The alternately arranged leaves are usually clustered at the tips of the rhizomes. These very large leaves (17-70 cm long and 10-40 cm wide) are heart-shaped (i.e. cordate) with wavy margins and rounded or abruptly pointed tips (i.e. obtuse or mucronate apices). They are borne on thick, spongy, stalks (i.e. petioles) 30-100 cm long with sheathed bases. These upright (i.e. erect) leaf stalks are joined to the undersides of leaf blades (i.e. the leaves are peltate). The typical form of this species has green leaves and leaf stalks. However, most naturalised plants are derived from ornamental cultivars and have purplish coloured leaf stalks. The leaf blades of these plants are often bluish-green (i.e. glaucous) or have purplish coloured veins."

Flowers and fruits 

"Separate male and female flowers are borne in elongated clusters on a fleshy central stalk, with the female flowers at the base and the male flowers towards the tip (i.e. the inflorescence is a spadix). These clusters (6-21 cm long) are mostly enclosed by a large greenish-yellow or yellow bract (i.e. spathe) 20-35 cm long and are borne on thick stalks (i.e. peduncles) 15-50 cm long. The spathe is fused together into a tube at the base (4-6 cm long), which hides the female flowers. These greenish-coloured female flowers are densely clustered in the lower 2-4.5 cm long section of the flower cluster, while the yellowish-coloured male flowers are densely clustered in the upper 2-4.5 cm long section of the flower cluster. There is a narrower section (1.5-4.5 cm long) between the male and female flowers that bears partially-formed (i.e. sterile) flowers. In the typical form of the species there is a also short section at the top of the flower cluster (1-3 cm long) that does not bear any flowers (i.e. an appendix), however this section is much larger (3-9 cm long) in naturalised plants in south-eastern Queensland.

As the fruit begin to mature the upper part of the spathe (i.e. blade) withers, while the lower section (i.e. spathe tube) persists. The fruit are small oval (i.e. ellipsoid) berries (3-5 mm long) that turn from green to orange or red as they mature. These fruit contain several egg-shaped (i.e. ovoid) seeds 1-1.5 mm long and 0.7-1 mm wide."

Reproduction and dispersal 

"This species reproduces by seed and vegetatively via its tubrous underground stems (i.e. rhizomes and corms).

Seeds are spread by birds and other animals that eat the fruit. The tuberous roots, corms and seeds are dispersed in dumped garden waste and by water during floods."

Similar species 

"The three varieties of taro (Colocasia esculenta) in Australia can be distinguished from each other by the following differences:

■Colocasia esculenta var. aquatilis (native to northern Australia) usually has green leaves and leaf stalks, and its corms are very small. Its flower clusters have a very short extension at the tip that is devoid of flowers (i.e. rudimentry appendix).

■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).
Taro (Colocasia esculenta) is also similar to similar to blue taro (Xanthosoma violaceum ) and the native cunjevoi (Alocasia brisbanensis). These species can be distinguished from each other by the following differences:

■taro (Colocasia esculenta) has green or purplish leaf stalks that have their stalks attached to their undersides (i.e. the leaves are peltate). It has thick, tuberous, creeping stems (i.e. corms).

■blue taro (Xanthosoma violaceum ) has purplish leaf stalks that have their stalks attached to their bases (i.e. the leaves are not peltate). It has thick, tuberous, creeping stems (i.e. corms).

■cunjevoi (Alocasia brisbanensis) has green leaf stalks that have their stalks attached to their bases (i.e. the leaves are not peltate). It eventually develops thick upright stems up to 1 m or more tall."