Bur Cactus
Opuntia salmiana
NEMBA category
English: Bur Cactus, Salm's Prickly Pear
Opuntia salmiana, commonly known as Bur Cactus or Salm's prickly pear, is a shrubby cactus species characterised by its elongated, cylindrical to slightly flattened pads and vibrant yellow or orange flowers. Native to South America, it has been introduced to various regions, including South Africa, where it has become an alien invasive species.
The plant thrives in arid and semi-arid environments, forming dense thickets that out-compete native vegetation and reduce biodiversity. Its ability to spread rapidly through both seed dispersal and vegetative reproduction from detached pads makes it difficult to control.
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Origins: South America
Overall Appearance: Opuntia salmiana is a shrubby cactus with a distinctive, sprawling growth habit. It features elongated, cylindrical to slightly flattened pads that are blue-green in colour, often with a waxy coating. The plant forms dense, impenetrable thickets, making it highly invasive in its introduced range. Typically grows to a height of 1–2 metres, though it can occasionally reach up to 3 metres under favourable conditions. The plant can spread 2–4 metres wide, forming large clumps due to its ability to propagate vegetatively.
Leaves: Like most cacti, Opuntia salmiana does not have true leaves. Instead, its photosynthetic function is carried out by its modified stems (pads). These pads are 10–30 cm long and 5–10 cm wide, cylindrical to slightly flattened, and covered in small, hair-like spines called glochids, which are highly irritating to the skin.
Flowers: The flowers are large, showy, and 5–7 cm in diameter, with bright yellow or orange petals. They are cup-shaped and appear at the edges of the pads. The flowers are visually striking and contribute to the plant's ornamental appeal. Flowering typically occurs in late spring to early summer (October to December in South Africa).
Fruits: The fruits are 4–6 cm long, oval to pear-shaped, and reddish-purple when ripe. They are fleshy and contain numerous small seeds. The fruits are edible and have a sweet taste, often used in traditional dishes and beverages in their native range.
Seeds: The seeds are small, 2–3 mm in diameter, and encased in the fruit's pulp. They are dispersed by animals that eat the fruit, as well as by water and human activity.
Bark: The plant does not have traditional bark. Instead, its pads are covered in a thick, waxy cuticle that helps reduce water loss, typical of cacti adapted to arid environments.
Wood: Opuntia salmiana does not produce woody tissue. Its structure is composed of succulent, water-storing pads.
Soil Type: The plant thrives in well-drained, sandy, or rocky soils. It is highly adaptable and can grow in poor, nutrient-deficient soils.
Aspect: Opuntia salmiana prefers full sun and is well-suited to hot, dry environments. It can tolerate partial shade but grows best in open, sunny areas.
Edible Parts: The fruits are edible and are consumed in some cultures. The pads (nopales) are also edible when young and tender, often used in salads or cooked dishes.
Poisonous Parts: The plant is not poisonous, but the glochids (tiny spines) on the pads can cause skin irritation and should be handled with care.
Uses:
- Ornamental: Grown for its attractive flowers and unique appearance.
- Food: Fruits and young pads are edible.
- Fodder: In some regions, it is used as emergency livestock feed during droughts.
Wildlife Interactions:
- Birds: Attracts birds that feed on its fruits, such as bulbuls and starlings.
- Insects: Pollinated by bees and other insects attracted to its bright flowers.
- Mammals: Small mammals and livestock may eat the fruits and pads, aiding in seed dispersal.
Ecological Impact:
Opuntia salmiana is a highly invasive species in South Africa, particularly in arid and semi-arid regions. It forms dense thickets that outcompete native vegetation, reduce biodiversity, and disrupt ecosystems. Its ability to spread rapidly through both seed dispersal and vegetative reproduction makes it difficult to control. Management efforts include mechanical removal, herbicide application, and biological control using cochineal insects (Dactylopius spp.).
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