Melaleuca viminalis (weeping bottlebrush / treurperdestert) is a listed Category 3 alien invasive plant species in the Gauteng province (as well as North West, Free state, Northern Cape and Western Cape), in terms of the 2014 Alien and Invasive Species Regulations of The National Environmental Management Biodiversity Act (NEMBA) (Act No. 10 of 2004). Land owners are prohibited from further planting, propagation or trade. Although mature specimens may remain, their seed must be prevented from spreading and saplings must be controlled in gardens. It is prohibited in riparian areas (within 32 m of the edge of a water course or wetland or the 1:100 year flood line, whichever is greatest), where it becomes a Category 1b invader. In the rest of the country, it is listed as Category 1b. Sterile cultivars or hybrids are not listed. 

Weeping bottlebrush along Moreletaspruit
Photo: Louise Kritzinger

Origin: Weeping bottlebrush, like most other Melaleuca species, is native to Australia. In its home range, it is endemic from Queensland to New South Wales. It was introduced to South Africa as an ornamental tree for its bright red flowers, along with M. citrinus (lemon bottlebrush / lemoenperdestert) and C. linearis (stiff-leaved bottlebrush / perdestert), which are also listed Category 3 invaders in Gauteng. It is particularly problematic along watercourses, such as the Moreletaspruit in the Bronberg region. Weeping bottlebrush is also naturalised in southern and eastern Africa and in other parts of the world, including India, certain Atlantic Ocean islands and the Mediterranean Sea, Central America and South Western USA. 

Description: A member of the family Myrtaceae (myrtle), it is a thornless, evergreen shrub to small tree, up to 8 m high with drooping branches and flowers. The bark is grey, flaky and rutted. Leaves are narrowly elongated and sharply pointed, alternately arranged, with new growth distinctly pinkish. Due to oil glands on the leaves, the plant is strongly aromatic, which also makes it flammable. Showy, bright red flowers are arranged in spikes towards the end of branches almost all year round. Small, round-shaped woody capsules contain up to nine viable seeds, making seed production very prolific. Conservatively, it can produce 10 000 seeds per tree after flowering.  

Leaves new growth
Photo: Louise Kritzinger

Impact: Weeping bottlebrush is highly invasive along river banks, wetlands and drainage culverts along roadsides, competing aggressively with indigenous riparian vegetation, impacting local biodiversity and altering riverine ecosystems. Seeds are water-dispersed and can spread to locations far away from the original tree.    

Control methods: No biological control agents have been identified. Small plants can be removed manually, while large specimens should be treated chemically after being cut down or ring-barked with herbicides containing glyphosate or amazapyr. It is important that with multi-stemmed trees, each stem must be treated. Care must be taken when working near aquatic environments, whereby glyphosate is the safer option. Monitoring for re-growth is essential.

Indigenous alternatives: Greyia sutherlandii (beacontree / baakhout), Erythrina lysistemon (coraltree / koraalboom), Halleria lucida (tree fuchsia / notsung), Schotia brachypetala (weeping boerbean / huilboerboon), Loxostylis alata (tarwood / teerhout) and Nuxia oppositifolia (river-elder / watervlier).

Inflorescence
Photo: Tiaan-Kotzé

Visit www.invasives.org.za for more information on alien and invasive plant and animal species. 

This article was sponsored by the Friends of Faerie Glen Nature Reserve