What Does It Look Like?
What is it?
Khaki Weed (Alternanthera pungens) is a prostrate (matt forming) creeping perennial (occasionally annual) herb with a deep woody taproot. The spreading stems are up to 500 – 600 mm long, reddish with soft silky hairs, often forming extensive mats and rooting at the nodes (leaf joints on the stem). Leaves are in opposite pairs of unequal size, 10-40 mm long, 10-20 cm wide, obovate (egg-shaped with the widest part near the tip) or circular, occasionally ovate (egg-shaped with the widest part near the base). Leaves are hairless or sparsely hairy especially near the base, prominently veined on underside, and shortly petiolate (with a short leaf stalk). Leaf margins are entire (without teeth), often with a short point at the tip VicFlora (2016).
The flowers are in axillary ovoid clusters, 6-10 mm long. Flowers surrounded by 3 bracts (leaf-like structures) and bracteoles 2–3 mm long, and are clustered together in between the leaves and the stem. The spikes are white, yellow or greenish when young and become straw coloured when mature. Each flower is 3.5–5 mm long and has 5 unequal segments with the 2 longest segments sharply pointed.
The fruit matures within the flower segments and bracts and the entire spike then detaches from the stem forming a prickly burr to about 10 mm long. This then breaks up into individual prickly fruit. There is one yellowish amber or brown, globular seed per fruit, 1-3 mm diameter (Miller & Schultz 1997; Parsons & Cuthbertson 2001; Navie 2004).
Recognition: This species can normally be recognised by the combination of the following characters; an annual prostrate (matt forming) herb; leaves – opposite pairs of unequal size, 10-40 mm long, 10-20 cm wide egg-sapped, deep green, hairless or sparsely hairy leaves; cream flowers are in ovoid clusters, 6-10 mm long with sharp points.
For further information and assistance with identification of Khaki Weed, contact the herbarium in your state or territory.
White, yellow or green.
Growth form (weed type/habit)
Where it currently grows? Preferred habitat
Khaki Weed (Alternanthera pungens) is found in tropical and subtropical regions growing mainly on light soils in areas of high temperatures. It also grows in cool temperate areas in southern Australia. Khaki Weed does particularly well colonising bare or disturbed areas and can be found in and around towns commonly occurring on nature strips, lawns, playing fields, caravan parks and saleyards (Parsons & Cuthbertson 2001). It is also found along road verges, crop and farm land, degraded pastures and disturbed natural vegetation (Spooner et al. 2007).
Are there similar species?
Khaki Weed (Alternanthera pungens) is somewhat similar to Bindy Eye (Soliva sessilis) and some of the Joyweeds (e.g. Alternanthera denticulata, Alternanthera nodiflora and Alternanthera nana). It is also similar to Gomphrena Weed or Soft Khaki Weed (Gomphrena celosioides) (Navie 2004), and small matweed (Guilleminea densa).
Gomphrena weed (Gomphrena celosioides) and small matweed (Guilleminea densa) may be distinguished by their lack of prickles, and gomphrena weed (Gomphrena celosioides) also by its larger whitish flower clusters that are borne at the tips of its branches (Brisbane City Council 2020).
Bindy Eye (Soliva sessilis) is a low-growing (i.e. prostrate) plant that produces prickles from its flower parts. However this species has very different, highly divided, leaves. Lesser Joyweed (Alternanthera denticulata), Common Joyweed (Alternanthera nodiflora) and Hairy Joyweed (Alternanthera nana) may have a low creeping habit and very similar flower clusters to Khaki Weed, but these species do not produce prickles. Gomphrena Weed may also be distinguished by its lack of prickles and by its larger, whitish-coloured, flower clusters that are borne at the tips of its branches (Navie 2004).