Disa cardinalis

H.P. Linder


Family:
Orchidaceae

Disa cardinalisDisa cardinalis is an attractive orchid with brilliant red flowers, found in Western Cape, South Africa. The species is not often seen in nature because of its limited distribution and specialized habitat (streambanks on the northern slopes of the Langeberg), but the species is very well known both as a potplant and as a parent of award-winning hybrids.

Description
Disa cardinalis is a recently described species in the D. tripetaloides group. The group, which also including the famous red disa D. uniflora, comprises D. tripetaloides, D. aurata and D. caulescens, which are evergreen stream-side plants in Western Cape (only D. tripetaloides ranges as far as southern KwaZulu-Natal). Like all related orchids, D. cardinalis has underground root tubers that give rise to a solitary stem. Plants form an underground network of slender stolons (creeping stems) which is often seen as a protection against flood damage, and these result in dense colonies. Foliage leaves of D. cardinalis are clustered at the base of the flowering stem which is about 300-600 mm long and bears up to twenty brilliant red and comparatively large flowers (up to 25 mm in diameter). The striking flowers appear between November and January. Flowering at this time of year is made possible by the stream-side habitat of the species, as all other habitats in the region are already dry.

Distribution
Disa cardinalis is only found on the dry, northern slopes of the Langeberg Mountains from about Barrydale to the gorge of the Gouritz River.

Derivation of name and historical aspects
Disa is a large genus of African terrestrial orchids and was described by the Swedish botanist P.J. Bergius in 1767. There are several theories regarding the derivation of its name, but it is most likely that the genus was originally named after Queen Disa in a famous Swedish saga. There are 132 Disa species in South Africa, the most well known being the 'pride of Table Mountain' or the 'red disa', D. uniflora - sometimes called the world's largest-flowered ground orchid.

In the 1970s a red Disa, thought to be a colour form of D. tripetaloides and referred to as var. coccinea, was common in cultivation and was extensively used in hybridization. Taxonomic studies of the Disa group by H.P. Linder showed that this form should be recognized as a distinct species which he described in 1980. However, it could not be called D. coccinea as this name had already been used before, and in view of the bright red flowers, he described it as D. cardinalis.

 Growing in habitat

Ecology
Habitat of Disa cardinalisLike the remaining species of the Disa tripetaloides group, D. cardinalis grows on the edges of perennial streams. However, the habitat of D. cardinalis is somewhat unique in that it lies within the arid Karoo (the other species of the D. tripetaloides group occur in the moist fynbos region). Plants of D. cardinalis frequently grow in full sun. While summer daytime temperatures can be very high, the nights are often remarkably cool.

The seeds of Disa cardinalis are fairly large compared to most other Disa species (1.1 versus 0.3 mm), and it has been suggested that they are dispersed by the streams next to which the plants grow. This water dispersal is very unusual in the orchid family (where the seeds are normally wind-dispersed) but is also known in D. uniflora where it has been studied in detail. However, occasional upstream wind dispersal must also take place in D. cardinalis, as its populations would otherwise continually migrate downstream.

The pollination of this species has not been observed as yet. However, the Mountain Pride butterfly Meneris (Aeropetes) tulbaghia, the pollinator of several other red and orange-red flowers, occurs in the area, and it was suggested that it could also be the pollinator of Disa cardinalis.

Uses and cultural aspects
Uses as medicinal plant or food source have not been recorded in this species. However, Disa cardinalis is extensively used in horticulture. This species exhibits robust growth and comparatively large and showy flowers which are all desirable features of potplants. Disa cardinalis is also extensively used in hybridizing. A list of popular hybrids is given in Crous (2003: 26).

Growing Disa cardinalis

Flowers of Disa cardinalisThe cultivation of Disa cardinalis and its hybrids is very similar to that of D. uniflora and the remaining species of the D. tripetaloides group. The plants of this group are by far the better-known disas in cultivation as they are comparatively easy to grow. However, both the specialized habitat requirements and the annual growth cycle have to be taken into account by the grower and certain rules have to be followed.

All orchids are strictly protected by law in South Africa, and it is therefore highly illegal to remove any plants from the wild. Fortunately, there are a number of specialist nurseries that stock Disa cardinalis, where plants for cultivation can be purchased.

The leafy shoot grows slowly throughout winter (June to October). Growth speeds up in spring and the flowering shoot emerges from the leaf rosette. A vital phase in the annual growth cycle takes place at flowering time with the formation of a replacement tuber (the old one will eventually die and with it the above-ground shoot), and any disturbance during this period, such as premature repotting, can be fatal. The leafy shoot emerges a few months after flowering.

Because of its habitat on the edge of mountain streams, Disa cardinalis is adapted to a rather cool environment. It is particularly essential to keep the soil cool in cultivation (below 20ºC in summer) which in nature is achieved by the cold mountain water. Summer daytime temperatures may well exceed 30ºC, to which the plants are also well adapted in their natural habitat in the Karoo. Adequate soil moisture, bright light, humidity above 60 % and good aeration are also essential requirements for a successful cultivation. Plants are best grown in small pots (10-15 cm) filled with a well-drained mixture of silica-grit, sand and palm fibre. They should be watered daily as the roots must never dry out. It is of utmost importance that the water is clean (i.e. very low in salts, for example rainwater) and of low pH (5-6). However, be careful not to over-water as this would lead to rapid rot! Repotting should be done in autumn in the southern hemisphere, which is a few months after flowering when the new shoots are already vigorous. Feed mainly in late winter and spring, and use a diluted inorganic fertilizer.

Disa cardinalis multiplies vegetatively by stolons which produce new plants and the species can therefore be propagated by division. However, the propagation by seeds is much more efficient. Seeds of D. cardinalis and related species can be sown directly on peat or moss and need not be raised on agar in sterile flasks like most other orchids. Seedling trays are covered with foil to provide extra humidity. As soon as the seedlings are sufficiently vigorous, they can be transferred to a seedling mix and later to the ordinary substrate. Flowers can be expected after two to three years.

There are various pests and diseases but many of them can be avoided by correct cultivation, e.g. adequate temperature, no over-watering, general cleanliness (removal of dead leaves). The greatest threat to any Disa collection are fungal infections. Stem and root rot can destroy a plant within a few days and should be controlled with adequate fungicides, and also preventative treatment is available. Aphids, red spider mites and thrips are often also a problem, the latter two especially if the growing environment is too warm.

For more information about orchids follow this link.

References

  • Crous, H. 2003. Some habitat notes on Disa cardinalis. Orchids South Africa 34: 24-26.
  • Linder, H.P. 1980. Disa cardinalis Linder (Orchidaceae), a new species from the Cape Province. Journal of South African Botany 46: 213-215.
  • Linder, H.P. 1981. Taxonomic studies on the Disinae. III. A revision of Disa Berg. excluding Sect. Micranthae Lindl. Contributions from the Bolus Herbarium 9: 1-370.
  • Linder, H.P. 1981. Disa cardinalis. The Flowering Plants of Africa 183: t. 1826.
  • Linder, H.P. & Kurzweil, H. 1999. Orchids of southern Africa. Balkema, Rotterdam.
  • Wodrich, K. 1997. Growing South African indigenous orchids. Balkema, Rotterdam.

    If you enjoyed this webpage, please record your vote.

    Excellent - I learnt a lot
    Good - I learnt something new

    H. Kurzweil
    Kirstenbosch Research Centre
    February 2004

     


To find out if SANBI has seed of this or other SA species, please email our seedroom.
This page forms part of the South African National Biodiversity Institute's plant information website www.plantzafrica.com.


SANBI Home