A small upright shrub growing up to 1.5 m tall. Its smooth stems have spines arranged in threes in the forks of the lower leaves. Its paired leaves (3.5-9 cm long and 8-12 mm wide) are narrow with a prominent reddish mid-vein. Its yellow flowers are borne in dense spike -like clusters at the tips of the branches. These flowers are subtended by relatively large overlapping bracts that are often purplish in colour.
Naturalised in some parts of northern Australia (i.e. in the coastal districts of the Northern Territory and in northern and south-eastern Queensland). Also naturalised on Christmas Island and possibly naturalised in the northern parts of Western Australia.
A weed of open woodlands, hillsides, riparian vegetation, roadsides, walking tracks, disturbed sites and waste areas.
A small upright (i.e. erect) shrub growing up to 1.5 m tall and forming a thorny thicket.
"Hophead barleria (Barleria lupulina) has occasionally escaped cultivation as a garden ornamental in south-eastern Queensland. It forms thorny thickets that are difficult to walk through and replace native species. A relatively large and dense infestation was recently detected growing in the understorey of a eucalypt forest on a hillside in the Brookfield area, in the western suburbs of Brisbane. This population has been targeted for eradication, due to the potential that this species has of becoming a serious environmental weed in the region.
Hophead barleria (Barleria lupulina) is also invasive in open woodland habitats and along watercourses in the Northern Territory and northern Queensland."
"The smooth stems are hairless (i.e. glabrous), faintly four-angled, and either green or reddish in colour. These stems have sharp spines that are borne in pairs in the lower leaf forks (i.e. axils). The slender spines are angled downwards (i.e. deflexed) and about 1-2 cm long.
The paired leaves are borne on short stalks (i.e. petioles) 2-3 mm long. These leaves (3.5-9.2 cm long and 8-12 mm wide) are elongated in shape (i.e. oblanceolate to narrowly obovate) with entire margins and a small spine at the tip. They are hairless (i.e. glabrous) and have a prominent mid-vein that is usually reddish in colour."
"The flowers are borne in dense spike-like clusters at the tips of the branches (i.e. in terminal spikes) and are subtended by relatively large overlapping bracts. Flowers emerge progressively from the base of the cluster, with the bracts hiding the young flower buds. These broad bracts (about 15 mm long and 12 mm wide) are green or purplish, particularly in the upper half, and come to a short point at the tip (i.e. they are shortly mucronate). The flowers have four elongated (i.e. lanceolate) sepals, the outer two of which are slightly larger (about 10 mm long) than the inner two (about 8 mm long). These sepals are hairy (i.e. pubescent) and tipped with tiny spines. The five petals are fused together at the base in a tube (i.e. corolla tube) about 3 cm long. They are bright yellow to apricot in colour and the petal lobes (i.e. corolla lobes) are about 1 cm long. Each flower also has four stamens and an ovary topped with a long style (about 3 cm long) ending in a tiny stigma. Two of the stamens are borne on stalks (i.e. filaments) about 2 cm long, and can be easily seen, while the other two are borne on shorter stalks and are hidden inside the flower tube.
The small capsules are pointed (i.e. ovoid-acuminate) and turn from green to brown in colour as they mature. These capsules contain one or two disc-shaped (i.e. discoid) seeds."
This species reproduces by seed, which are spread short distances when the capsules explosively release their seeds. Seeds may also be dispersed by water and in dumped garden waste.
"Hophead barleria (Barleria lupulina) is very similar to porcupine flower (Barleria prionitis). These two species can be distinguished from each other by the following differences:
■hophead barleria (Barleria lupulina) has narrow leaves with a prominent reddish-coloured midvein.
■porcupine flower (Barleria prionitis) has relatively broad leaves that do not have a prominent reddish-coloured midvein.
Another closely related species, yellow barleria (Barleria micans), is occasionally grown in gardens. It can be distinguished from barleria (Barleria lupulina) by the lack of spines on its stems."