Dense-thorned Bitter Apple
Solanum sisymbriifolium
NEMBA category
Wild Tomato, Sticky Nightshade (English), Wildetamatie, Tamatiedissel, Digdoringbitterappel (Afrikaans)
English: Dense-thorned Bitter Apple, Sticky Nightshade, Red Buffalo-bur, Wild Tomato, Fire-and-ice Plant
Afrikaans: Kleefnagskade, Digdoring-bitterappel, Wildetamatie, Tamatiedissel, Digdoringbitterappel
Historical scientific names: Solanum balbisii, Solanum subinerme
Solanum sisymbriifolium, commonly known as Sticky Nightshade or Dense-thorned Bitter Apple, is a spiny, herbaceous perennial or annual plant. It is easily recognised by its deeply lobed, hairy leaves covered in sharp yellow thorns, its pale blue to white flowers, and its small, red, tomato-like berries.
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Origin:
South America (Brazil, Paraguay, Uruguay, Argentina).
Distinguishing features:
Extremely dense covering of sharp, yellowish thorns on stems, leaves, and even flower stalks.
Deeply lobed, often hairy leaves.
Pale blue, purplish, or white star-shaped flowers.
Small, red, round berries encased within a spiny calyx.
Very sticky (glandular hairy) stems and leaves.
Overall appearance:
Solanum sisymbriifolium is an upright, bushy plant that can be an annual or a short-lived perennial, often becoming quite large and branched. It is characterised by its incredibly thorny nature, with spines covering almost all parts of the plant.
Height:
Typically grows 0.5 to 2 metres tall, but can sometimes reach up to 2.5 metres.
Width:
It can spread to a width of 1 to 1.5 metres, forming dense thickets.
Leaves:
The leaves are alternately arranged, deeply lobed (pinnatifid or pinnatisect), and can be up to 30 cm long and 15 cm wide. They are covered with soft, sticky (glandular) hairs, especially on the underside, and are armed with numerous sharp, yellowish thorns along the veins on both surfaces, especially the midrib. The lobes are often irregular and coarsely toothed.
Flowers:
The flowers are star-shaped with five petals, typically pale blue to violet, sometimes white, and about 2-3 cm in diameter. They have a prominent cluster of yellow stamens in the centre. The flowers are borne in clusters (racemes) at the ends of branches or in leaf axils. Solanum sisymbriifolium flowers are hermaphroditic, containing both male and female reproductive parts, so it is not dioecious.
Flowering season:
In South Africa, it can flower for much of the year, particularly from spring to autumn (around September to May), with peak flowering during the warmer months.
Fruits:
The fruits are small, round berries, 1.5-2.5 cm in diameter, resembling miniature tomatoes. They start green and ripen to a bright red or orange-red colour. Each berry is enclosed within a persistent, spiny calyx (the leafy part that surrounds the base of the flower and fruit).
Seeds:
The seeds are small, flattened, yellowish to brownish, and kidney-shaped or irregularly oval, typically 2-3 mm long. Each berry can contain numerous seeds (up to 100 or more), and they remain viable in the soil for a long time.
Bark:
As a herbaceous plant, it does not develop bark in the typical sense. The stems are green or purplish, covered with glandular hairs and prominent, sharp yellowish thorns.
Thorns:
This is one of its most defining features. The plant is heavily armed with numerous, straight, sharp, yellowish or orange thorns, typically 0.5-1.5 cm long. These thorns cover the stems, leaves (especially the midrib and veins), calyces (fruit coverings), and even flower stalks.
Wood:
Not applicable, as it is a herbaceous plant.
Roots:
It has a taproot system with many fibrous lateral roots, allowing it to access moisture efficiently.
Soil type:
It is highly adaptable and can grow in a wide variety of soil types, including sandy, loamy, and clay soils, particularly those that are disturbed or degraded. It thrives in well-drained soils but can tolerate some moisture.
Aspect:
Prefers full sun but can tolerate partial shade. It is relatively drought-tolerant once established but performs best with moderate moisture.
Edibility:
The fruits, though resembling small tomatoes, are generally considered non-edible. While some sources suggest ripened fruits might be consumed cautiously in very small quantities in its native range, they are not widely eaten and are often considered unpalatable due to stickiness and bitterness. It's best to avoid consumption entirely due to potential toxicity and the presence of harmful compounds.
Toxicity:
All parts of Solanum sisymbriifolium, especially the unripe fruits and foliage, contain steroidal glycoalkaloids (e.g., solasodine), which are toxic to humans and livestock if ingested in sufficient quantities. Symptoms of poisoning can include nausea, vomiting, diarrhoea, abdominal pain, drowsiness, and neurological effects. The thorns can also cause mechanical injury.
Uses:
Due to its invasive nature and toxicity, it has limited beneficial uses in South Africa. In its native range, it has been explored for medicinal properties (with extreme caution) and as a trap crop for nematodes (soil worms) in agriculture, particularly for potatoes, due to its ability to attract and then hinder their reproduction.
Ecology:
As a highly invasive species in South Africa, Solanum sisymbriifolium poses significant ecological threats:
Forms impenetrable thickets: Its dense, spiny growth makes areas inaccessible to humans, livestock, and wildlife, hindering movement and grazing.
Outcompetes indigenous vegetation: Its rapid growth, prolific seed production, and adaptability allow it to quickly colonise disturbed areas, rangelands, pastures, roadsides, and agricultural lands, displacing native plants and reducing biodiversity.
Reduces grazing capacity: The dense thorns and unpalatability of the foliage make invaded areas unsuitable for livestock.
Impacts agriculture: It can act as an alternative host for pests and diseases of cultivated Solanum crops (like potatoes, tomatoes, aubergines), increasing agricultural problems.
Soil degradation: While not as dramatic as some woody invaders, its dense stands can alter soil conditions.
Distribution and habitat:
In South Africa, Solanum sisymbriifolium is widespread and particularly problematic in the summer rainfall regions. It is found in most provinces, including Gauteng, Mpumalanga, Limpopo, KwaZulu-Natal, Eastern Cape, Free State, and North West. It thrives in disturbed areas such as roadsides, railway lines, waste ground, overgrazed pastures, cultivated fields (especially potato and maize fields), and degraded 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, or from "solor," meaning "to soothe."
The species name sisymbriifolium means "with leaves like Sisymbrium" (a genus of mustard plants), referring to the lobed leaf shape.
Common names like "Sticky Nightshade" refer to its sticky hairs and relation to the nightshade family. "Dense-thorned Bitter Apple" aptly describes its spiny nature and fruit appearance.
Historical aspects:
Solanum sisymbriifolium was accidentally introduced to South Africa, likely as a contaminant in agricultural produce or fodder, possibly during the late 19th or early 20th century. It quickly established itself due to its aggressive growth habit, prolific seed production, and adaptability to disturbed environments. Despite its potential as a trap crop in its native range, its invasive nature in South Africa has led to its classification as a noxious weed, requiring control.
Interesting facts:
This plant is like a porcupine in plant form! It's absolutely covered in super sharp, yellow thorns, making it a nightmare to touch. Seriously, don't try to pick its flowers!
Its little red berries look exactly like tiny tomatoes, but do NOT eat them! They're actually quite poisonous and can make you really sick. It's a classic case of "looks can be deceiving."
This plant is a bit of a sticky mess – its stems and leaves are covered in tiny hairs that make it feel tacky to the touch. This stickiness probably helps it catch small insects or deter larger ones.
Despite its scary thorns, it has pretty pale blue or white flowers that are quite delicate. It's a real contrast between beauty and beast!
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