Inkberry
Cestrum laevigatum
NEMBA category
English: Inkberry, Cestrum, Smooth-leafed Cestrum, Green Cestrum, Jessamine, Black Nightshade, Chinese Inkberry
Afrikaans: Inkbessiebos, Grootblaar Inkbessie
Historical scientific names: Cestrum parqui var. laevigatum
Misapplied scientific names: Cestrum parqui
Cestrum laevigatum, commonly known as Inkberry or Smooth-leafed Cestrum, is a shrub that looks innocent enough with its glossy green leaves and delicate greenish flowers, but hides a dark secret – its shiny, purple-black berries are dangerously poisonous!
It's a fast-growing, evergreen bush or small tree with an often untidy, sprawling habit. While its flowers might seem unassuming, its ability to quickly take over and its toxic nature make it a significant threat to wildlife and pastures.
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Origin:
Native to South America, specifically Brazil, Paraguay, and Argentina.
Distinguishing features:
Glossy, smooth leaves: Dark green, lance-shaped to elliptical leaves that are smooth to the touch, and often have an unpleasant smell when crushed.
Greenish-yellow tubular flowers: Small, trumpet-shaped flowers, often appearing in clusters, usually greenish-yellow, sometimes tinged with purple.
Shiny purple-black berries: Small, round to egg-shaped, glossy, dark purple or black berries that are highly attractive to birds.
Strong unpleasant odour: The whole plant, especially when bruised, gives off a distinctive, often unpleasant, smell.
Overall appearance:
A fast-growing, multi-stemmed, evergreen shrub or small tree with an often untidy or sprawling growth habit. It forms dense thickets with its many branches.
Height:
Typically grows to between 2 and 4 metres tall, but can sometimes reach up to 6 metres.
Width:
Can spread 2 to 4 metres wide, forming dense clumps due to suckering.
Leaves:
Simple, alternate, and entire (smooth-edged). They are lance-shaped to elliptical, with a pointed tip and a smooth, somewhat glossy texture. The upper surface is dark green, while the underside is paler. They measure about 5 to 15 centimetres long and 1.5 to 5 centimetres wide. When bruised or crushed, the leaves emit a strong, unpleasant, often acrid or pungent odour.
Flowers:
Small, tubular, greenish-yellow, sometimes with a purplish tinge, about 1.5 to 2.5 centimetres long. They are bell-shaped and occur in dense clusters (panicles) in the leaf axils (where the leaf joins the stem) or at the ends of branches. They are mildly fragrant, particularly at night. The plant is hermaphroditic, with both male and female parts in each flower.
Flowering season:
In South Africa, it has a prolonged flowering period, generally from late spring through autumn (around October to April), but can flower almost year-round in frost-free, warm regions like the Eastern Cape.
Fruits:
Small, fleshy, spherical to egg-shaped berries, 6 to 10 millimetres in diameter. They are glossy and turn from green to shiny purple-black when ripe. Each berry contains several seeds. These berries are highly attractive to birds.
Seeds:
Small, angular, dark brown to blackish seeds, typically 3 to 6 seeds are found within each berry. They are easily dispersed by birds that eat the fruit.
Bark:
The bark on young stems is smooth and greenish-brown, sometimes purplish. On older stems and trunks, the bark can become somewhat corky, slightly furrowed, and greyish.
Thorns:
This species does not have thorns.
Wood:
The stems are relatively soft, brittle, and flexible when young, becoming woody and more rigid with age.
Roots:
Develops a robust, fibrous root system that spreads widely. It also readily produces root suckers, allowing it to form dense clonal colonies.
Soil type:
Highly adaptable and can tolerate a wide range of soil types, including poor, degraded, and compacted soils. It prefers moist, well-drained conditions but is relatively drought-tolerant once established.
Aspect:
Prefers full sun to partial shade. It tolerates a variety of environmental conditions but thrives in warm, moist climates.
Ediblity:
NOT EDIBLE. All parts of this plant, particularly the berries and leaves, are highly poisonous to humans and animals.
Toxicity:
HIGHLY TOXIC to humans and livestock. All parts of Cestrum laevigatum contain various neurotoxic alkaloids, including solanine-like compounds. Ingestion can cause severe symptoms such as vomiting, diarrhoea, abdominal pain, tremors, muscle weakness, loss of coordination, convulsions, and even paralysis. It is a common cause of poisoning in cattle, sheep, and goats, leading to significant livestock losses. Children are particularly vulnerable due to the attractive appearance of the berries.
Uses:
It was introduced to South Africa primarily as an ornamental garden plant due to its attractive foliage and ease of growth, and sometimes used for hedging. However, because of its high toxicity and aggressive invasive nature, its planting is now strongly discouraged and regulated.
Ecology:
As an alien invasive plant in South Africa, Cestrum laevigatum is a highly aggressive invader. It forms dense, impenetrable thickets that outcompete and displace indigenous vegetation, leading to a significant loss of biodiversity. Its success is driven by its rapid growth rate, prolific production of seeds (which are effectively dispersed by birds eating the berries), and its ability to spread vegetatively through root suckers. The toxicity of the plant is a major ecological concern, as it can poison both wild animals and domestic livestock that browse on its leaves or consume its berries, often leading to fatalities. It degrades natural habitats and reduces the availability of suitable forage for native herbivores.
Distribution and habitat:
Widespread and problematic throughout the higher rainfall regions of South Africa. It is a declared invader in all provinces. It is particularly prevalent in KwaZulu-Natal, Eastern Cape (common in coastal areas, riverbanks, and disturbed bushland around Kenton-on-Sea), Mpumalanga, Limpopo, and Gauteng. It invades disturbed sites, roadsides, forest margins, plantations, riverbanks, grasslands, and pastures.
Derivation of name:
The genus name Cestrum is believed to come from the Greek word 'kestron', which was an ancient name for a plant, or potentially refers to a burin or engraving tool, perhaps alluding to the flower's shape.
The species epithet laevigatum is Latin for "smooth" or "polished," referring to the smooth, glossy surface of its leaves.
The common name "Inkberry" refers to the dark, juicy berries that resemble ink.
Historical aspects:
Cestrum laevigatum was introduced to South Africa as an ornamental plant in the late 19th or early 20th century. Its hardiness, rapid growth, and the appeal of its berries led to its widespread planting in gardens. However, its aggressive spread into natural areas and its well-documented toxicity to livestock quickly established it as a serious environmental and agricultural weed. Incidents of poisoning in livestock have been recorded for many decades, highlighting its dangerous nature.
NEMBA status:
Category 1b invasive species. This means it must be controlled and eradicated where possible. It is illegal to plant, propagate, import, or otherwise possess this plant without a permit.
Interesting facts:
Don't let its pretty berries fool you! This plant is known as the "Inkberry" because its dark fruits look like drops of ink, but they are incredibly poisonous to both humans and animals.
It's a bit of a sneaky invader – birds love to eat its berries, and then they fly off and "plant" the seeds everywhere, helping the Inkberry spread far and wide!
Even without flowers, you might be able to tell this plant is around because its leaves release a rather unpleasant smell when you crush them.
This plant is so tough that it can grow in places where other plants struggle, quickly taking over disturbed areas and forming dense, impenetrable thickets.
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