Most of the research into renosterbos ecology was conducted by the great Cape botanist Margaret Levyns (1929). The plant has an extremely deep taproot which can grow to well over 6 m. Its ability to grow in very arid areas is probably due to the taproot accessing ground water. It is flammable but killed by fire, so is dependent on its seed for regeneration. It thus has to produce many seeds, thousands of which are borne on each twig. After being shed in winter, seeds become dormant and do not germinate until at least the following year, or several years later. This may be an adaptation to enhance dispersal. Seeds are dispersed by wind, having a feathery pappus to catch the breeze.

Germination and establishment are facilitated by disturbance in the form of fire or clearing of vegetation. Until the taproot is established, the seedlings are extremely sensitive and are killed by drought or shade. Shading from other plants, especially grasses, would have prevented this plant from reaching large densities under natural conditions.

It is not known how it is pollinated, but it appears to be adapted to wind pollination, and genetic studies indicate that it probably outcrosses (does not self-fertilise). Although it is reported to be unpalatable to stock, it has its own specialist browser - the small flightless renosterbos locust Lentula obtusifrons. This insect is confined to the Eastern Cape and eats only renosterbos. Several other insects appear to have associations with renosterbos. Many of these are small and not well known. Scale insects form galls, spittle bugs are often found on the twigs, and small flies parasitise the embryos.

Renosterbos is one of the most widely distributed of an indigenous Cape group which includes Stoebe (slangbos), Disparago, Metalasia (blombos), Phaenocoma (strawberry everlasting) and a few other little-known species. This group is in turn a member of the globally distributed daisy tribe of everlastings, including Helichrysum and Leontopodium (edelweiss).