Bugweed
Solanum mauritianum
NEMBA category
English: Bugweed, Bug Tree, Wild Tobacco, Woolly Nightshade, Tobacco Weed, Flannel Weed
Afrikaans: Luisboom, Tabakbos, Groot Bitterappel
Xhosa: umGqomogqomo
Zulu: umBangabanga, uBhoqo
Historical scientific names: Solanum auriculatum, Solanum verbascifolium var. auriculatum
Solanum mauritianum, commonly known as Bugweed or Wild Tobacco, is a fast-growing, large evergreen shrub or small tree. It is easily identified by its large, velvety, grey-green leaves, clusters of purple star-shaped flowers, and dense bunches of green berries that ripen to yellow-orange.
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Origin:
South America (Brazil, Argentina, Paraguay, and Uruguay).
Distinguishing features:
Large, velvety, grey-green leaves covered in soft, star-shaped hairs.
Distinctive "ear-like" lobes (stipules) at the base of the leaf stalks.
Clusters of purple (sometimes blue or white) star-shaped flowers.
Dense bunches of round, green to yellow-orange berries.
Strong, unpleasant, 'buggy' smell when leaves are crushed.
Overall appearance:
Solanum mauritianum is a robust, upright, and often multi-stemmed evergreen shrub or small tree. It has a rather unkempt, bushy appearance, forming dense stands where it invades.
Height:
Typically grows 2 to 4 metres tall, but can reach up to 10 metres in ideal conditions.
Width:
It can spread to a width of 2 to 5 metres, forming dense thickets.
Leaves:
The leaves are large (up to 30 cm long and 25 cm wide), oval to egg-shaped, and covered on both surfaces with soft, greyish-white, star-shaped (stellate) hairs, giving them a velvety texture and a dull, grey-green colour. They have entire (smooth) margins. A key identifying feature is the presence of two small, ear-like lobes (stipules) at the base of the leaf stalks. When crushed, the leaves emit a strong, unpleasant odour, often described as 'buggy'.
Flowers:
The flowers are small (1.5-2.5 cm in diameter), star-shaped, with five petals, typically bright purple, sometimes blue or white. They have prominent yellow stamens in the centre. The flowers are borne in dense, branched clusters (cymes) at the ends of branches or in the leaf axils. Solanum mauritianum flowers are hermaphroditic, containing both male and female reproductive parts, so it is not dioecious.
Flowering season:
In South Africa, it has a prolonged flowering season, typically from spring through autumn (around August to May), with peak flowering often in spring and early summer. It can flower intermittently throughout the year in warm, moist conditions.
Fruits:
The fruits are small, round berries, about 1-1.5 cm in diameter. They are initially green and ripen to a dull yellow-orange or brownish-yellow colour. They are produced in very dense, hanging clusters (up to 50 berries per cluster) and remain on the plant for a long time. Each berry contains numerous seeds.
Seeds:
The seeds are small, flattened, disc-shaped, light brown, and typically 1-2 mm in diameter. Each berry can contain 150-250 seeds. The seeds are highly viable and can remain viable in the soil for several years, forming a persistent seed bank.
Bark:
The bark on young stems is green and hairy. As the plant matures, the bark on the main stem becomes brownish-grey, often with small, raised lenticels (pores).
Thorns:
This plant does not have thorns.
Wood:
The wood is soft, light, and brittle. It is not considered commercially valuable timber.
Roots:
It has a shallow, spreading, fibrous root system, making it relatively easy to uproot when young but forming dense mats that compete effectively with other plants.
Soil type:
It is highly adaptable and can grow in a wide range of soil types, including sandy, loamy, and clay soils, often thriving in disturbed, degraded, or nutrient-poor conditions. It prefers well-drained soils but can tolerate some moisture.
Aspect:
Prefers full sun to partial shade. It is not tolerant of severe frost but can recover from light frost. It thrives in high rainfall areas.
Edibility:
All parts of Solanum mauritianum, especially the unripe fruits and foliage, are highly toxic and not edible. Despite looking like small tomatoes, they should never be consumed.
Toxicity:
All parts of Solanum mauritianum are highly toxic due to the presence of steroidal glycoalkaloids, primarily solasodine and solamargine. Ingestion can cause severe poisoning in humans and livestock. Symptoms include gastrointestinal upset (nausea, vomiting, abdominal pain, diarrhoea), headache, fever, and in severe cases, central nervous system effects. The berries are particularly attractive to children, posing a significant risk. The fine hairs on the leaves and stems can also cause skin and respiratory irritation.
Uses:
Due to its invasive nature and toxicity, it has virtually no beneficial uses in South Africa. Historically, in some regions, it was used as a traditional medicine (with extreme caution due to toxicity), and the leaves were sometimes used to repel insects (hence "Bugweed").
Ecology:
As one of South Africa's most problematic alien invasive plants, Solanum mauritianum causes severe ecological damage by:
Forming dense, impenetrable thickets: It rapidly colonises disturbed areas, forest margins, plantations, roadsides, and riparian zones, outcompeting and shading out indigenous vegetation, leading to a dramatic reduction in biodiversity.
Habitat transformation: It alters the structure and composition of natural ecosystems, creating monocultures that are unsuitable for native flora and fauna.
Reducing grazing land: Its unpalatability and toxicity make invaded pastures unusable for livestock.
Impact on agriculture and forestry: It can invade plantations (e.g., commercial timber, fruit orchards), reducing productivity and increasing management costs.
Poisoning risk: Its toxic berries are dispersed by birds and other animals, further spreading the plant. While some birds appear tolerant, there is a risk of poisoning to livestock and potentially other wildlife. Its leaves can also cause respiratory irritation to humans, particularly forestry workers.
Distribution and habitat:
In South Africa, Solanum mauritianum is widespread and highly invasive, particularly in the moist, higher rainfall regions. It is found in all nine provinces, with very significant invasions in KwaZulu-Natal, Mpumalanga, Eastern Cape, Limpopo, Gauteng, and the Western Cape. It commonly invades forest margins, plantations (especially commercial timber plantations), riparian areas, roadsides, waste areas, and disturbed natural veld.
Derivation of name:
The genus name Solanum is derived from the Latin "solamen," meaning "comfort" or "relief," possibly referring to the medicinal properties of some species.
The species name mauritianum means "from Mauritius," referring to the island of Mauritius in the Indian Ocean, where it was first described, although its native range is South America.
Common names like "Bugweed" and "Tobacco Weed" refer to the unpleasant smell of its crushed leaves and its large, tobacco-like foliage, respectively. "Wild Tobacco" is also widely used.
Historical aspects:
Solanum mauritianum was introduced to South Africa as an ornamental garden plant in the mid-19th century, valued for its fast growth and lush foliage. Its rapid spread was initially overlooked, but its aggressive invasive nature soon became apparent, especially in commercial timber plantations where it became a major weed. It is now one of South Africa's most problematic invasive species, requiring extensive control efforts, including biological control, to manage its spread and mitigate its environmental and economic impact.
Interesting facts:
This plant is nicknamed "Bugweed" because when you crush its leaves, they smell like a squashed bug! Definitely not a pleasant aroma.
It's a real super-spreader! Its seeds are like tiny, prolific producers, with each berry containing hundreds of them, and birds love to eat the berries, spreading the seeds far and wide.
Despite looking like a soft, velvety plant, all parts of Bugweed are poisonous, especially those round, yellowy-orange berries. So, no snacking on these "wild tomatoes"!
This plant grows incredibly fast, especially in places where the ground has been disturbed. It's like a plant sprinter, quickly taking over open areas and shading out everything else.
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