Skills books › Introduction to Gardening in South Africa

Indigenous plants and invasive aliens: what to plant and what to remove

Plant what belongs here, and remove what does not. Indigenous plants are adapted to South Africa's soils, rainfall, frost and drought, and they support its birds and insects. Invasive alien plants spread into veld, rivers and mountains, use water and crowd out everything else.

Why plant indigenous?

Indigenous plants from the right region:

• use less water once established;
• survive the local frost and heat;
• need less fertiliser and spraying;
• support birds, bees and butterflies.

"Indigenous" does not automatically mean "suits my garden". A Cape protea from acid sand will die in alkaline Free State clay. Choose plants from your own region, or from a similar climate and soil.

How to choose

1. Region and climate: rainfall season, frost and heat.
2. Sun or shade.
3. Soil: sandy, loam or clay, acid or alkaline.
4. How much water the spot will get.
5. Mature height and spread.
6. Purpose: screen, shade, colour, ground cover or food for birds.

Starter ideas by region

Frosty summer-rainfall gardens (Highveld and Free State)

• Small trees: karee, wild olive, white stinkwood, sweet thorn.
• Shrubs: sagewood, wild dagga, wild rosemary.
• Perennials and bulbs: agapanthus, red-hot pokers, wild garlic, dietes, gazania.
• Ground covers: vygies, bulbine.
• Succulents: frost-hardy aloes, crassula.

Winter-rainfall gardens (Cape Town): pincushions, leucadendrons, buchu, restios, pelargoniums and watsonias.

Subtropical gardens (Durban): strelitzia, plectranthus, clivia in shade, plumbago, Cape honeysuckle and coral trees.

A local indigenous nursery or a National Botanical Garden will show you what thrives nearby.

Garden plants that became invaders

Many invasive plants came in as garden ornamentals. Examples include:

• lantana, which forms thorny thickets and poisons livestock;
• bugweed, spread by birds;
• pompom weed, which invades Highveld grassland;
• pampas grass, along rivers and wetlands;
• queen of the night cactus;
• water hyacinth, which chokes dams and rivers.

Invasive trees such as wattles, pines and eucalypts along rivers use far more water than the plants they replace.

What the law says

Invasive species are listed in four categories under the National Environmental Management: Biodiversity Act. The lists change, so check the current version.

• Category 1a: must be eradicated.
• Category 1b: must be controlled and prevented from spreading.
• Category 2: allowed only with a permit, in a set area.
• Category 3: existing plants may stay, except near rivers and wetlands, but may not be planted, propagated, sold or given away.

In practice:

• do not plant, sell or pass on cuttings of listed plants;
• a landowner must control category 1b plants on the property;
• when a property is sold, the seller must tell the buyer in writing which listed invasive species are on it;
• a garden service that plants a listed species for a client is breaking the law, even if the client asks.

Removing invasive plants

• Hand-pull seedlings when the soil is moist.
• Dig out small plants with all their roots.
• Cut and treat the stump of trees and shrubs that resprout, using a registered herbicide exactly as its label directs.

Work in this order:

1. Remove young and scattered plants first.
2. Then tackle the dense stands.
3. Bag seed heads. Do not put them on a cool compost heap.
4. Replant or mulch the cleared ground at once.
5. Follow up every few months for two to three years, because seeds in the soil keep germinating.

This guide is based on Chapter 9 of Introduction to Gardening in South Africa, which also covers gardening for birds, bees and butterflies.