hairy commelina

Commelina benghalensis
Vine
Alternate
Simple
Blue
Green

A long-lived herbaceous plant with creeping or semi-upright stems growing up to 30 cm tall. Its hairy stems are somewhat fleshy and regularly produce roots at their joints. Its alternately arranged leaves (2-9 cm long) are hairy and have a sheath that is the topped with long reddish or brownish hairs. Its bright blue flowers are borne in small clusters and are subtended by a hairy bract (1-1.5 cm long). This bract is fused together on both sides, with an opening at the top. Its small capsules (4-6 mm long) contain five seeds.

Common names 
Also known as: Benghal dayflower, commelina, day flower, dayflower, dew flower, hairy commelina, hairy wandering Jew, Indian dayflower, jio, tropical spiderwort, wandering Jew,
Family 
Commelinaceae
Deciduous 
No
Flowering time 
year round
Native/Exotic 
Exotic
Origin 
Native to Africa, the Arabian Peninsula, the Indian Sub-continent, southern China, Japan and south-eastern Asia.
Notifiable 
No
Council declaration 
SIL – Special Investigation List
Known distribution 

Widely naturalised in Australia, but primarily found in the northern and eastern parts of the country. It is widespread in Queensland and naturalised in northern New South Wales (i.e. north from the Comboyne area) and the northern parts of the Northern Territory.

Habitat 

A weed of riparian vegetation, gardens, roadsides, disturbed sites, waste areas and crops.

Habit 

A long-lived (i.e. perennial) herbaceous plant with creeping or semi-upright (i.e. prostrate to ascending) stems growing up to 30 cm tall.

Impact and control methods 

"This species is an environmental weed in south-eastern Queensland and northern New South Wales. Hairy wandering Jew (Commelina benghalensis) is listed among the 200 most invasive plants in south-eastern Queensland and is a common weed of waterways and riparian areas in the region.

It has also invaded conservation areas in northern New South Wales (e.g. the Ballina Nature Reserve) and is an important weed of crops in eastern Australia."

Stem and leaves 

"The branching stems are somewhat fleshy (i.e. succulent) and are sparsely to moderately covered with hairs (i.e. pubescent). These stems (15-40 cm long) regularly produce roots at their joints (i.e. nodes) if they are in contact with the soil surface (i.e. they are stoloniferous). Plants sometimes also produce whitish-coloured underground stems (i.e. rhizomes) with reduced leaves.

The alternately arranged leaves have a sheath at the base (1-2 cm long), which encloses the stem. At the top of this sheath is a line of long reddish or brownish coloured hairs. The leaf blades (2-9 cm long and 1-4 cm wide) are egg-shaped in outline (i.e. ovate), oval (i.e. elliptic) or slightly elongated in shape with entire margins and rounded or pointed tips (i.e. obtuse or acute apices). These leaves are covered with short hairs (i.e. they are pubescent) and are usually light green in colour."

Flowers and fruits 

"The flowers are borne in small clusters (i.e. cymes) in the upper leaf forks that are subtended by a folded hairy bract (i.e. a pubescent spathe). This spathe (1-1.5 cm long) is somewhat triangular in shape and fused together on both sides, with an opening at the top. The flowers have three small pale bluish coloured sepals and three larger bright blue or dark blue petals. Two of the petals are conspicuous (4-8 mm long), while the other is smaller. Each flower has three stamens and three partially-formed stamens (i.e. staminodes). One of the fully-formed stamens has yellow anthers and the other two have blue anthers, while the partially-formed stamens have yellow cross-shaped 'anthers' (i.e. cruciform antherodes). The flowers also have an ovary topped with a slender blue style. Specialized flowers (i.e. cleistogamous flowers) are also produced along the underground stems (i.e. rhizomes).

The fruit are small pear-shaped (i.e. pyriform) capsules that contain five seeds. These capsules (4-6 mm long) turn from green to pale brown as they ripen, and split open when fully mature (i.e. they are dehiscent). The dark brown, blackish or greyish-brown seeds (1.7-2.5 mm long) have pitted or furrowed (i.e. rugose or reticulate) surfaces. Slightly different seeds are produced in the underground flowers. These 'subterranean seeds' usually remain viable for longer periods than the normal ones."

Reproduction and dispersal 

"This species reproduces by seed and also spreads vegetatively via its creeping stems (i.e. stolons).

The seeds and stem segments are dispersed by water, while the seeds may also be dispersed in contaminated soil and agricultural produce."

Similar species 

"Hairy wandering Jew (Commelina benghalensis) is very similar to the native wandering Jews (Commelina diffusa and Commelina lanceolata). These species can be distinguished by the following differences:

■hairy wandering Jew (Commelina benghalensis) has relatively broad leaf blades (10-45 mm wide) that are often somewhat hairy. Its flowers are bright blue and have rounded petals. It generally grows in moist and/or shady habitats.

■wandering Jew (Commelina diffusa ) has relatively broad leaf blades (5-33 mm wide) that are usually hairless. Its flowers are usually bright blue and have rounded petals. It generally grows in moist and/or shady habitats.

■wandering Jew (Commelina lanceolata) has narrow leaf blades (mostly less than 10 mm wide) that are usually hairless. Its flowers are usually bright blue and have rounded petals. It generally grows in the understorey of open sclerophyll forests.
In the vegetative stage it is also relatively similar to trad (Tradescantia fluminensis ), which has glossy green, hairless and relatively thick and fleshy leaf blades. Its flowers are white and have pointed petals."