Nicotiana glauca, in Afrikaans commonly known as jantwak (John tobacco), is an exotic, a declared weed in South Africa, obliging landowners to eradicate it when found on their properties. It is a slender shrub or small tree up to 6 m tall.
The young stems are green, while some dead branches are usually present. The large ovate leaves are alternate, ascending on long stalks. They are glaucous and smooth with entire margins. Glauca, the specific name from Latin means blue-grey or emerald green.
The narrowly tubular, yellow flowers grow in loose, drooping clusters. They have pointy calyces covering a short part of the corolla tube. Flower dimensions are 5 cm long and 1 cm wide. The small seeds drop early, ready for action.
This plant has spread widely from South America across Africa, Asia, southern Europe, Australia and New Zealand, often a nuisance. Introduced into South Africa deliberately from Argentina to bring trees to the arid inland parts in 1845, it does provide a little shade but has also invaded.
The habitat is riverine areas, seasonal watercourses, floodplains and road reserves in arid regions (Coates Palgrave, 2002; Shearing and Van Heerden, 2008; iSpot).