The idea behind the 70/30 rule is straightforward: dedicate at least seventy per cent of your garden to plants indigenous to your region and allow thirty per cent for well-behaved non-native ornamentals. The outcome is a garden that actively supports local biodiversity, reduces maintenance and water demands, and still leaves room for the plants you genuinely love that happen not to be indigenous.

This principle, developed from research by ecology professor Doug Tallamy, has been widely adopted in conservation-oriented gardening internationally. In a South African context, it is particularly relevant: South Africa is one of the world’s most botanically diverse countries, home to over twenty thousand plant species, and is also one of the most threatened by invasive species. A garden that reflects this diversity does more than look beautiful.

Why indigenous plants matter

Indigenous plants have co-evolved with local wildlife over thousands of years, developing relationships that exotic plants simply cannot replicate. An indigenous tree or shrub in a South African garden is connected to a network of insects, birds and other wildlife that depend on it in specific ways. Moths lay their eggs on particular plant species; those eggs hatch into caterpillars that become food for garden birds; those birds in turn attract the insectivores and raptors that control pest populations. Each native plant added to a garden strengthens this network.

Non-indigenous plants, even those that are not invasive, typically provide minimal value to local wildlife: they may attract generalist pollinators to their flowers, but they rarely support the specific insects, larvae and birds that indigenous species do. A garden dominated by exotic ornamentals is beautiful but essentially silent in ecological terms.

The 70 per cent: what to plant

For the seventy per cent indigenous portion, choose plants that suit your specific conditions. South Africa’s diverse climates mean that what is indigenous in the Western Cape differs significantly from what grows naturally in Gauteng or KwaZulu-Natal. The most important principle is to match plants to your local conditions rather than fighting your soil, rainfall and temperature with plants that need constant intervention.

For trees and shrubs, the halleria lucida (tree fuchsia) is exceptional: it flowers almost year-round, produces berries that attract fruit-eating birds, and provides nectar for sunbirds. Dombeya rotundifolia (wild pear) flowers prolifically in winter and early spring, providing food when little else is available. Searsia lancea (karee) is a graceful, drought-tolerant tree that provides excellent structure and habitat. For flowering shrubs, plumbago auriculata is one of the most reliably useful indigenous plants available in any South African garden, flowering for months and attracting butterflies and bees.

For the perennial layer, agapanthus, dietes grandiflora (wild iris), kniphofia (red hot poker), bulbinella and various restios and ornamental grasses provide structure and seasonal interest with minimal maintenance. Strelitzia reginae (bird of paradise) is both spectacular and tougher than it looks once established. For ground cover, indigenous gazania, vygies (mesembryanthemums) and pelargoniums provide colour, weed suppression and significant pollinator value.

The 30 per cent: what to allow

The thirty per cent non-native portion is where your personal favourites and the plants that fill awkward gaps can go. The only non-negotiable restriction is that the plants in this category must not be invasive. Check the South African NEMBA (National Environmental Management: Biodiversity Act) listed invasive species and avoid any Category 1, 2 or 3 plants. This list includes lantana, bugweed, pampas grass, certain acacia species, kikuyu grass in some contexts, and many others that are widely sold but actively harmful to SA ecosystems.

Well-behaved non-native plants that perform a useful role in the garden without invasive tendencies include roses, most bulbs such as tulips, daffodils and irises, lavender, rosemary, camellias and many culinary herbs. Vegetables and herbs in a kitchen garden effectively count as your non-native thirty per cent, which is a practical reason to convert any remaining ornamental beds near the vegetable garden to indigenous plantings.

Other eco-friendly habits that support the garden

Beyond the plant selection itself, a few practices significantly enhance the ecological value of any garden. Leaving a layer of fallen leaves on the soil over winter rather than raking them away provides shelter for overwintering insects and ground-dwelling beneficial invertebrates. A small brush pile or log pile creates habitat for garden snakes, lizards and the insects they eat. A birdbath or small water feature provides the water that garden birds and insects need year-round, and in a South African summer, a shaded water source is more valuable than almost any planted feature. Eliminating chemical pesticides from the garden altogether allows beneficial insect populations to stabilise naturally. A garden with a healthy ecosystem does much of its own pest control.

Where to start

If your current garden is entirely non-native, you do not need to remove everything at once. Begin by identifying the lawn areas or beds that offer the least return, either aesthetically or practically, and replace those with indigenous species first. The front garden or any lawn that serves no active purpose is an ideal starting point. Converting even one or two beds to indigenous planting each season will shift the garden’s ecological balance meaningfully over time.

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