Farmer's Weekly (South Africa)
Know your invasive species
This article looks at the beefwood, balloon vine and other species that, by law, have to be controlled or eradicated.
Every year, invasive plants rob South Africa of an estimated 1,44 billion cubic metres of water. According to Henko Vlok of the Sustainability Initiative of South Africa, this is enough for 3,38 million households of four inhabitants each for a year, or to irrigate 120 000ha of cropland.
With South Africa a waterscarce country, controlling of invasive alien plants (IAPs) is key to protecting our water resources.
IAPs are exotic, non-indigenous or non-native to an ecosystem. Due to resistance to local control factors and a lack of natural enemies, these plants tend to spread aggressively.
The Alien and Invasive Species Regulations of the National Environmental Management: Biodiversity Act 10 of 2004 (NEMBA) divides invasive plant species into four categories:
• Category 1a
IAPs that may not be owned, imported into South Africa, grown, moved, sold, given as a gift or dumped in a waterway. Species in this category have to be controlled on a property, and Department of Environmental Affairs officials must be allowed access to monitor or assist with control.
• Category 1b
Major invaders that may need government assistance to remove.
• Category 2
Invasive species that can remain in a garden only with a permit.
• Category 3
IAPs that can remain in a garden without a permit. However, they cannot be propagated or sold. In riparian zones or wetlands, all Category 3 plants become Category 1b plants. Some species to look out for:
BAILEY’S WATTLE
(Acacia baileyana) An evergreen tree reaching 3m to 6m in height and with small branches covered in greyish or silvery-blue foliage. Bright yellow flowers bloom from July to September. Fruits are greyish-brown pods about 100mm long.
Bailey’s wattle competes with indigenous species in forested areas and along river banks, and has the potential to replace these species.
• Invasive status:
NEMBA Category 3. A problem in the Western Cape, Eastern Cape, KwaZulu-Natal (KZN), Free State, Mpumalanga and Gauteng.
BALLOON VINE
(Cardiospermum grandiflorum [Sapindaceae])
A perennial, slightly woody climber with tendrils reaching 5m and higher. The balloon vine drapes itself over trees, smothering indigenous species.
The stems are usually covered with bristly hairs. The bright green leaves are strongly serrated and sometimes hairy.
• Invasive status:
NEMBA Category 1b. A problem in KZN, Gauteng, Mpumalanga and Limpopo.
BEEFWOOD
(Casuarina cunninghamiana) A tall, evergreen tree reaching up to 40m high with arching, slender branches. The male flowers appear as yellowish spikes and female flowers as reddish heads from September to April. The tree also produces small, brown, woody cones about 20mm long.
The beefwood competes with and replaces indigenous species, while stands along watercourses can reduce stream flow.
• Invasive status:
NEMBA Category 2. A problem in the Western and Eastern Cape, KZN, Mpumalanga and Limpopo.
BELHAMBRA
(Phytolacca dioica [Phytolaccaceae])
Also known as the monkey grape, this large, soft-wooded, semi-evergreen tree can grow up to 20m high, with a short, buttressed trunk and a rounded crown.
Bright, oval-shaped leaves about 70mm long end in a gentle point with smooth margins. The berry-like fruits are initially green, then turn black.
It invades savanna, fynbos, coastal bush, river banks, roadsides and urban open spaces, where it competes with indigenous species. Because of its large size, even a single tree can have a significant effect on a natural ecosystem. One example of this is where indigenous birds neglect the dispersal of indigenous plants because of their preference for the fruits of this alien species. • Invasive status:
NEMBA Category 3. A problem in the Western Cape, Eastern Cape, KZN and Gauteng.
BIRD OF PARADISE FLOWER
(Caesalpinia gilliesii) A deciduous shrub that grows up to 5m tall depending on rainfall. Branchlets and inflorescence are covered with velvety hairs and dense blackish or brownish glands.
C. gilliesii competes with indigenous species, and its seeds and green seed pods are toxic, causing severe vomiting and other abdominal symptoms. • Invasive status:
NEMBA Category 1b. A problem in the Eastern Cape, Free State, North West and Northern Cape.
BLACK IRONBARK
( Eucalyptus sideroxylon) A small to medium-sized, evergreen tree reaching
15m to 26m high with a moderately spreading crown and shallow roots that may outcompete adjacent plants.
The bark, as its name indicates, is hard and deeply furrowed. E. sideroxylon flowers in winter, producing cream, pink or deep rose-red flowers. It invades riparian habitats.
• Invasive status:
NEMBA Category 2. A problem in Gauteng, Mpumalanga, KZN, Limpopo and North West.
BLACK LOCUST
( Robinia pseudoacacia) This deciduous tree can reach up to 12m high, and has an oval or rounded crown and darkbrown, deeply furrowed bark.
Small, bright-green leaves become yellow in autumn. White, fragrant flowers in drooping sprays bloom from September to November.
It competes with and replaces indigenous species. Dense stands are formed mainly by suckering from the roots and can cover large areas; stands along watercourses restrict access to water by domestic and wild animals.
The seeds, leaves and inner bark are toxic to humans and livestock.
• Invasive status:
NEMBA Category 1b. A problem in all provinces of South Africa.
• Sources: Retrieved from ‘Hortgro.co.za/news/impactsand-control-of-invasive-alienplants-in-south-africa; capetowninvasives.org.za; www.invasives.org.za. The section ‘Legislation’ will enable you to download the NEMBA Invasive Species Regulations, Declaration of Invasive Species forms and other key documents.