| Scientific Name | Disa lugens Bolus var. lugens | Higher Classification | Monocotyledons | Family | ORCHIDACEAE | Synonyms | Herschelia lugens (Bolus) Kraenzl., Herschelianthe lugens (Bolus) Rauschert | Common Names | Blue Bonnet Disa (e) |
National Status | Status and Criteria | Vulnerable C2a(i) | Assessment Date | 2022/05/27 | Assessor(s) | L. von Staden, W.R. Liltved, E.G.H. Oliver & T.A. Oliver | Justification | A widespread and formerly common taxon that is becoming increasingly rare due to habitat destruction. Subpopulations are scattered and typically small. The largest subpopulation consists of around 1000 plants, but subpopulations are typically much smaller, generally consisting of fewer than 50 plants. With no more than 25 subpopulations known, the population size is therefore estimated to be under 3500 mature individuals. It is undergoing a rapid decline along the Cape coast due to urban and coastal development and alien plant invasion. It therefore qualifies as Vulnerable under criterion C. |
Distribution | Endemism | South African endemic | Provincial distribution | Eastern Cape, Western Cape | Range | This taxon has a distribution ranging from the Western Cape province to the Eastern Cape, where it ranges from the Cape Peninsula to Somerset East and Cathcart. |
Habitat and Ecology | Major system | Terrestrial | Major habitats | Amathole Montane Grassland, Cape Flats Dune Strandveld, Algoa Sandstone Fynbos, Kouga Grassy Sandstone Fynbos, Kouga Sandstone Fynbos, South Kammanassie Sandstone Fynbos, Tsitsikamma Sandstone Fynbos, South Langeberg Sandstone Fynbos, North Langeberg Sandstone Fynbos, Overberg Sandstone Fynbos, Suurberg Quartzite Fynbos, Albertinia Sand Fynbos, Cape Flats Sand Fynbos, Atlantis Sand Fynbos, Hartenbos Dune Thicket | Description | It is localised on coastal sand flats and dry mountain sides and can be found in fynbos and grassland at an altitude ranging from near sea level to 1,500m. |
Threats | | Urban development has caused the loss of most historically known subpopulations on the Cape Flats; the last specimens were collected around the 1970s. Urban development is an ongoing threat around rapidly expanding city centres such as Port Elizabeth, and all remaining coastal populations are potentially threatened by the development of holiday resorts/beach housing.
In the Eastern Cape, livestock overgrazing is a potential threat to this species. It may possibly decline in response to heavy overgrazing, but subpopulations subjected to moderate grazing and good rangeland management practices appear to be thriving.
Agriculture has probably caused past declines in the Bredasdorp area — small populations now remain on habitat fragments "surrounded by a sea of wheat fields" (Liltved and Johnson, 2012). Agriculture remains an ongoing potential threat in the Humansdorp area.
Commercial harvesting of thatching reed is threatening coastal populations in the Albertinia district. This species is often found growing amidst Restio tussocks (Liltved and Johnson, 2012). Linder (1981) believes the species is not dependent on restio tussocks for growth, as specimens in cultivation were able to grow independently of restios.
Invasive alien species threaten all remaining habitat fragments on the Cape Flats, even within protected areas where continual clearing of invasive aliens is required. Invasive species are also a problem in other coastal subpopulations, specifically around Humansdorp (Liltved and Johnson, 2012).
Plant-pollinator mutualisms are currently being broken down as a result of small, fragmented subpopulations. Subpopulations in the Bredasdorp area seem to suffer from unsuccessful pollination, as very poor fruit set has been observed (Liltved and Johnson, 2012). |
Population | This is a very widespread taxon, but it has become extremely rare due to habitat loss, particularly on the coastal lowlands. A large number of historical records indicate that it was once common in the sandplain fynbos of the Cape Flats, but it was last recorded in this area in the 1970s and is now suspected to be locally extinct. Currently, there are between 15 and 25 remaining subpopulations, and subpopulation size estimates for 18 of these indicate that subpopulations are generally very small, consisting of fewer than 200 mature individuals, and often only single flowering plants are observed. Flowering is not fire-dependent; this species is adapted to flower in mature vegetation (Liltved and Johnson 2012). In 2007, a large subpopulation of between 500 and 1000 mature individuals was found in the Cathcart region of the Eastern Cape. The total population size is estimated to be fewer than 3500 mature individuals.
| Population trend | Decreasing |
Assessment History |
Taxon assessed |
Status and Criteria |
Citation/Red List version | | Disa lugens Bolus var. lugens | EN C2a(i) | 2012.1 | | Disa lugens Bolus var. lugens | EN C2a(i) | Raimondo et al. (2009) | | Disa lugens Bolus var. lugens | Lower Risk - Near Threatened | Victor (2002) | | Herschelianthe lugens (Bolus) Rauschert | Vulnerable | Hilton-Taylor (1996) | | Herschelia lugens (Bolus) Kraenzl. | Endangered | Hall et al. (1980) | |
Bibliography | Hall, A.V., De Winter, M., De Winter, B. and Van Oosterhout, S.A.M. 1980. Threatened plants of southern Africa. South African National Scienctific Programmes Report 45. CSIR, Pretoria.
Hilton-Taylor, C. 1996. Red data list of southern African plants. Strelitzia 4. South African National Botanical Institute, Pretoria.
Johnson, S. and Bytebier, B. 2015. Orchids of South Africa: A field guide. Struik Nature, Cape Town.
Liltved, W.R. and Johnson, S.D. Unpublished. The Cape Orchids - Wild orchids of the Cape Floral Kingdom.
Linder, H.P. 1981. Taxonomic studies in the Disinae. III. A revision of Disa Berg. excluding sect. Micranthae Lindl. Contributions from the Bolus Herbarium 9:1-370.
Linder, H.P. and Kurzweil, H. 1999. Orchids of southern Africa. A.A. Balkema, Rotterdam.
Low, A.B. 1979. Whither Cape Flats? Veld & Flora 65(3):83-87.
Raimondo, D., von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. and Manyama, P.A. 2009. Red List of South African Plants. Strelitzia 25. South African National Biodiversity Institute, Pretoria.
Victor, J.E. 2002. South Africa. In: J.S. Golding (ed), Southern African plant Red Data Lists. Southern African Botanical Diversity Network Report 14 (pp. 93-120), SABONET, Pretoria.
Victor, J.E. and Dold, A.P. 2003. Threatened plants of the Albany Centre of Floristic Endemism, South Africa. South African Journal of Science 99:437-446.
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Citation | | von Staden, L., Liltved, W.R., Oliver, E.G.H. & Oliver, T.A. 2022. Disa lugens Bolus var. lugens. National Assessment: Red List of South African Plants version . Accessed on 2025/04/14 |
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