Rooibos Tea is a traditional herbal drink from South Africa, not marketed internationally. It is made from the leaves of the Rooibos Plant, Aspalathus linearis, a type of Cape Gorse which grows wild in dry areas of the northwestern part of the Fynbos Biome, part of the wider Cape Floristic Region. Although traditionally harvested from wild plants, the modern Rooibos industry is built around large scale cultivation of the plant, with only a tiny amount of the total crop harvested from the wild.
Thus the Rooibos Plant is considered to be an economically significant plant in South Africa. Although the commercial harvest is tied to agricultural production, this the wild population preserves a wider genetic heritage, which may become important should the commercial crop be threatened by disease or climate change. However, while quite a lot of research has been published into Rooibos, most of this relates to commercial cultivation, leaving us with little understanding of the ecology, distribution, or conservation status of the wild plants.
In a paper published in the South African Journal of Science on 26 November 2025, Tineke Kraaij of the Natural Resource Science and Management Cluster at Nelson Mandela University, Vernon Visser of the Centre for Statistics in Ecology, Environment and Conservation, and National Institute for Theoretical and Computational Sciences, at the University of Cape Town, and Gerhard Pretorius of NaturaLibra Environmental Services, present the results of a study which looked at the current distribution, potential distribution, population size, and threats to the population size of Wild Rooibos Plants in South Africa, with a view to creating a baseline against which future monitoring of the species could be measured.
Rooiboss is grows in areas with cold wet winters and hot dry summers, with annual rainfall levels of between 300 and 600 mm, and at elevations of between 450 and 900 m. It is found as far north as Vanrhynsdorp and as far south as Betty's Bay and the Cape Peninsula, and anecdotally grows as far east as Riviersonderend and Bredasdorp,
Wild Rooibos is an extremely variable species (potentially being a species cluster - a group of closely related species difficult to tell apart - rather than a true species), and can be difficult to differentiate from closely related African Gorse species such as Golden Tea, Aspalathus pendula, or Lebeck's Roiibos, Aspalathus lebeckioides. Wild Rooibos also has several different ecotypes, strains of the plant with different morphologies and environmental preferences, further complicating efforts to understand the distribution of the species.
The ecotypes of Wild Rooibos vary in habit, fire-survival strategy, vegetative and reproductive morphology, biochemistry, and genetics. They can be loosely grouped into four main forms, 'Erect' or 'Upright', 'Prostrate', 'Bush' or 'Shrub', and 'Tree' (although 'Tree' is sometimes regarded as a variant on the 'Erect' or 'Upright' form). A 'Salignus' form is also sometimes recognised, this having a Willow-like growth with multiple lanky stems reaching 2-3 m tall and a sparse canopy. The Prostrate and Shrub forms are wider than they are tall, and tend to have many branches close to the ground, and can resprout after a fire. The Erect, Tree, and Saliginus forms are tall, and only regrow from seeds. In addition to these, there is the commercially grown 'Nortier' form, a cultivar bred from the Erect form, which is tall like its parent, but also has the dense branching of the Bush form, giving it a large harvestable biomass.
Exemplary images of the different ecotypes or growth forms of Wild Rooibos, Aspalathus linearis, namely the (a) Bush or Shrub form, (b) Prostrate form, (c) Erect (including Upright or Tree) form, and (d) Salignus form. Kraaij et al. (2025).
These different ecotypes have different distributions. The Bush, Prostrate and Tree types occur towards the northern part of the species’ range, and the Prostrate, Erect and Salignus types toward the south. The Erect and Salignus types favour higher elevations, above 400-600 m. The Bush ecotype is predominant in areas with low rainfall (less than 200 mm per year), while the Salignus ecotype favours wetter areas (more than 500 mm per year), and lower elevations. Different ecotypes often coexist in the same region, but seldom close to one-another.
Kraaij et al. built up a map of the distribution of Wild Rooibos and its various ecotypes, using data from the Global Biodiversity Information Facility and CapeNature databases, previously published research, and fieldwork carried out by Gerhard Pretorius. As much as possible, sites with historic records of the plants were visited to establish their continuing presence (or absence). Additional observations were made along roads connecting historic observation sites.
This data was then used to build a model of the potential distribution of the species, and the Bush, Prostrate, Erect, and Saligus ecotypes. This was achieved by mapping the presence of the plants against a range of variables, including precipitation in the warmest quarter; precipitation in the coldest quarter; maximum temperature of the warmest month; minimum temperature of the coldest month; topographical slope; soil electrical conductivity; soil potassium, sodium, phosphorus, carbon, and nitrogen levels, soil pH; and the proportion of sand in the soil.
Of the 235 sites where the species was historically recorded, it was found to now be absent from 30, and present at 47. In addition, 99 new locations where the species was present were identified. The species was not found at an outlier north of Nieuwoudtville and one east of Vanrhynsdorp, and some locations around Citrusdal, not was it found south of Malmesbury, at Franschoek, on the Cape Peninsula, or in the Gordon’s Bay and Betty’s Bay areas. It was confirmed at De Doorns, the easternmost location where it was previously recorded. Kraaij et al. note that the absence of the species at a site where it was historically recorded does not imply local extinction; it is possible that the previous records were miss-identifications. Notably, the habitat at some of these locations appeared completely unsuitable for Rooibos, with very steep slopes, clay soils, or wetlands, and a plant assemblage different from that associated with Rooibos plants. Some records of the plant in southern areas listed on iNaturalist could be verified, suggesting that it is not absent from the claimed southern extent of its range, but the species mainly occurs in the area between Nieuwoudtville in the north, Groot Winterhoek in the south, Wupperthal and the Tra-Tra mountains in the east, and just southeast of Graafwater in the west.
Results of field verification of historical location records of Wild Rooibos, showing where Rooibos was present, absent or not verified, as well as new location records. Kraaij et al. (2025).
The Wild Rooibos population was predicted to extend from Nieuwoudtville in the north to just southeast of Ceres, with the bulk of its distribution around Clanwilliam and Citrusdal, which was largely in line with predictions based upon previous reports. In total the species occupied an area of about 6000 km², with individual ecotypes occupying areas of between 1500 and 2500 km². The Salignus ectotype was the most abundant, predicted to occupy an area of about 254 600 km², followed by the Prostrate ecotype, 161 200 km², the Bush ecotype, 121 100 km², and the Erect ecotype, 119 900 km². Because each ecotype and the species as a whole were modelled separately, the species total does equal the total for each ecotype minus the overlap between different ecotypes.
Overlap between ecotypes was only substantial in the core area of the distribution range. The Bush and Prostrate ecotypes had roughly similar distributions, extending east and south of the core area. The Erect and Salignus ecotypes had distributions extending west and north of the core area, with the Salignus ecotype predicted to extend furthest west, beyond Piketberg. The Salignus ecotype was also predicted to be found in the south, around Ceres.
The distribution of the different ecotypes appeared to be driven by different factors. The distribution of the Bush and Prostrate ecotypes appeared to be influenced by the coldest cool period temperature, with both ecotypes able to cope with sub-zero temperatures. Warm season precipitation was clearly important to these ecotypes as well, with both favouring low summer precipitation. The distribution of the Erect and Salignus ecotypes was most strongly influenced by the concentration of potassium in the soil, with both ecotypes favouring very low concentrations. The Erect ecotype also appeared to need low soil conductivity. The distribution of both Erect and Prostrate Ecotypes was also influenced by the concentration of carbon in the soil with both ecotypes favouring very low levels. Kraaij et al. note that high winter temperatures and wet summers favour the growth of pathogenic Oomycetes such as Pythium spp. and Phytophthora cinnamomi, which are known pests of farmed Rooibos.
Kraaij et al. also produce estimated population sizes for the species and each ecotype. They again note that the total for the species does not match the total for each ecotype added together, as these were calculated separately. Three estimates for each population were made, based upon the minimum, mean, and maximum density of the plants. For the species as a whole, the minimum population was estimated at 14.7 million plants, while the mean was 1.78 billion plants, and the maximum was 17.0 billion plants. The most abundant ecotype, Salignus, was estimated to have a minimum population of 144 million plants, a mean population of 390 million plants, and a maximum population of 630 million plants. For the Prostrate ecotype the figures were, minimum 4.35 million plants, mean 863 million plants, and maximum 4.66 million plants. For the Bush ecotype the figures were minimum 13.3 million plants, mean 325 million plants, and maximum 1.34 billion plants. Finally, for the Erect ecotype, the figures were minimum 3.00 million, mean 189 million, and maximum 833 million plants.
Kraaij et al. recommend, however, that these figures be taken with a good deal of caution, as characterising the species distribution and abundance in the landscape was challenging in many cases, with significant implications for the population estimates. The density of Prostrate plants was particularly hard to estimate, particularly when it was interspersed with other plants. The species has a highly irregular distribution across its range, with plants often forming dense clumps in the midst of apparently similar and equally habitable, but unoccupied, landscapes. Both the size and density of individual populations varied a great deal from site to site. Furthermore, most populations were detected from a moving vehicle, requiring a minimum density for observation; it is possible that less dense populations were overlooked. Finally, Rooibos plants grow in a landscape prone to periodic burning. This does not appear to damage the population as a whole, but the plants do take time to recover after a fire, so their presence is likely to have been missed in areas which had recently burned.
Given these constraints, Kraaij et al. estimate that the populations of the species and each ecotype are probably towards the lower ends of their estimated numbers, but that more detailed surveys of each population would be needed to confirm this.
Much of the population of Wold Rooibos appears to be on protected land. Kraaij estimate that 27% of the total population is found on state or private protected areas, with 38% of the Prostrate ecotype, 33% of the Salignus ecotype, 28% of the Bush ecotype, and 20% of the Erect ecotype occurring on protected land.
About 40% of the Wild Rooiboss population was found to be growing in areas where Kraaij et al. considered that it faced no threats. Another 13% was found in areas where it was prone to illegal harvesting, although this was not thought to present a major threat to the species. About 28% of the population was growing in areas where land transformation presented a threat, although much of this land was probably unsuitable for conservation, and was likely to receive some protection from legislation preventing the clearing of natural vegetation. About 4% of the land where the species grew is potentially threatened by overgrazing, although this does not appear to present a direct threat to Wild Rooibos plants. About 15% of the sites were threatened by invasive plants, particularly Dodder, Cuscuta campestris, a parasitic climbing plant from North America, which can target a wide range of hosts and which is a problematic invasive species in several parts of the world. Cultivated Rooibos fields are known to be prone to invasion by Golden Wreath Wattle, Acacia saligna, and Cyclops Wattle, Acacia cyclops, but while these are a problem in Rooibos fields, they do not seem to be a problem in the natural setting. Potentially, climate change could alter the fire regime in the areas where Wild Rooibos grows. However, the species currently grows in areas where fires are fairly infrequent, with the interval between fires typically significantly longer than the regrowth of the plants, so any shift in fire regime would have to be significant to cause a problem.
Climate change could also potentially alter rainfall patterns and temperature in areas where Wild Rooiboss grows. Since these are variables known to affect the distribution of the plants, this could potentially have a major impact on the species, particularly if winters become warmer and wetter. Two of the populations visited during the study appeared to have suffered widespread mortality events following high summer rainfall events in the summer before being visited. Cultivated Rooibos is also known to be intolerant of waterlogged soils, requiring farmers to implement careful drainage schemes. Since a wetter climate is a predicted outcome of a warming climate in the Western Cape, this could be a major threat to the future of the species.
Wild Rooiboss does not appear to be at risk from hybridisation. The various ecotypes do not appear to interbreed, even when in close proximity to one-another. Potentially each ecotype could be threatened by inbreeding depression if populations become isolated. As it stands, geneflow within the species is not really understood, though it is likely that geographical barriers such as wide rivers and mountain ranges present a barrier to pollination, and the main distributors of the seeds of the plants are Ants, which do not tend to move long distances. Despite the variety of ecotypes, Wild Rooiboss does not show a great deal of genetic diversity as a species, with even less diversity in the southern part of its range. This lack of diversity could potentially present a threat to the species, and should be considered carefully during any conservation efforts.
There are more than 9000 fields of Cultivated Rooiboss in South Africa, with 4181 occurring within the natural range of the species as calculated by Kraaij et al. Of the 146 Wild Rooibos populations varified, 55 were found to be within 1 km of Cultivated Rooibos fields. Theoretically, hybridisation between Wild and Cultivated Rooibos is possible, but this was not observed, Cultivated Rooibos plants do not persist well after cultivation ceases, which, combined with the apparently limited gene flow between ecotypes, suggests that hybridisation with the Cultivated form does not present a major threat to Wild Rooiboss populations.
Wild Rooibos has a limited and fragmented distribution, but within this range appears to be common. The total wild population of the species is estimated to be more than 15 million plants. About 27% of the species distribution lies within protected areas. The species does not appear to be threatened by illegal overharvesting, invasive plants, overgrazing, or fire regimes, nor by hybridisation with the Cultivated form. The potential for habitat transformation appears to present only a minor threat to the species. By far the greatest threat to Wild Rooibos appears to be the potential effects of global warming, potentially bringing warmer, wetter conditions unfavourable to the species. This could well cause the range inhabited by the species to contract, with little potential for migration to better climates without Human intervention.
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