Cape Sundew

===Habit=== D. capensis is a perennial herb forming a rosette typically in diameter, although occasionally up to . Its narrow, oblong leaves are held semi-erect. In summer, the plant produces one or two relatively tall inflorescences, each with between 15 and 30 flowers. The petals are typically pale purple.

D. capensis is quite variable across its range and several distinct forms have been informally identified. Peter D'Amato described four forms in his 1998 book The Savage Garden: Cultivating Carnivorous Plants: *D. capensis "Typical" with red-tentacled leaves long, and forming a scrambling stem *D. capensis "Narrow" with narrow leaves and less tendency to form a stem *D. capensis "Alba" similar to the "Narrow" form but with white flowers and pale tentacles *D. capensis "Red" similar to the "Narrow" form but entirely reddish-maroon in colour when growing in bright light, with deep pink flowers Robert Gibson noted the difficulty of assigning unlabelled plants to any of the informally described forms, due to short descriptions and the plants' variation in response to growing conditions. He detailed nine different forms: {| class="wikitable mw-collapsible mw-collapsed" |+ informally described by Gibson (2020) !Form !Habit !Leaves !Petiole !Lamina !Flowers !Stigmas !Stem !Localities |- |Wide-leaved |Robust |Green, underside sparsely covered with eglandular hairs |>3 mm wide, about 60% width of lamina |>3 mm, up to 8mm wide |Large, ~3 cm, usually dark purple |Irregularly obovate to elliptic, widening conspicuously from terete style segments |Conspicuous, to 15 cm |Western part of Western Cape: Silvermine Nature Reserve; Vogelgat Private Nature Reserve; former Bergvliet Farm |- |Narrow-leaved |Typical |Olive green to reddish, to about 12 cm long, underside sparsely covered with eglandular hairs |<=3 mm |<=3 mm, similar length to petiole and up to twice the width |~2 cm, pale purple |Terete to narrowly ovate |None, or up to 5 cm in older plants |Typical form in the wild |- |Red-leaved |Typical |Vibrant red under bright illumination, underside with few eglandular hairs |As narrow-leaved |As narrow-leaved |Up to 2 cm, style segments dark purple |Irregularly ovate |As narrow-leaved |Primarily Gifberg, but also Travellers Rest, Koue Bokkeveld plateau and Table Mountain |- |White-flowered |Typical |Golden green; tentacles with colourless stalks and green to pale red glands |As narrow-leaved |As narrow-leaved |10–14 mm, white petals |Moderately expanded |(not described) |Appears to have emerged spontaneously in cultivation |- |Mini |Compact |Olive-green, congested |1.5–2 mm |3–4 mm |Up to 2 cm, dark purple, on disproportionately tall scape |(not described) |At most a few cm long |High mountain areas near Ceres, Bainskloof (Matroosberg), upper slopes of Baviaanskloof between 1000 and 1800 m |- |Traveller's Rest |Giant |Green or fully red, very large (rosettes to ~30 cm) |Longer than lamina, about 2 mm wide |About 3 mm wide |About 1.5 cm, pale purple, style segments terete | |(not described) |Banks of Doring River at Traveller's Rest, east of Clanwilliam |- |Paddle-shape leaved (1) |Sparse, reminiscent of D. anglica |Green |~2 mm |~6 mm |(not described) |(not described) |(not described) |Very wet site at Gydo Pass near Ceres, ~1000m |- |Paddle-shape leaved (2) |Open with distinct internodes |Green |(as previous?) |(as previous?) |(not described) |(not described) |Conspicuous |Bainskloof Pass, also possibly Waaihoekskloof near Ceres, and Montague Pass. |- |Paddle-shape leaved (3) |Compact |To 6 cm long, spirally arranged, underside with abundant eglandular hairs |To 1 mm wide |To 3 mm wide |Up to 1.6 cm wide, petals dark purple |Dark purple, irregularly obovate |Formed only very slowly |In cultivation, origin not known |} Gibson also noted occasional plants of the 'narrow-leaved' form with enlarged bracteoles with insect-trapping hairs; and some red-leaved plants developing a row of insect-trapping hairs on the petals.

====Morphology==== D. capensis has elongated, roughly rectangular leaves with a distinct petiole typically similar in length to the lamina, although in some growth forms it may be significantly longer."}} Drosera species exhibit numerous different types of glandular trichomes (hairs). In addition to the large 'tentacles' involved in prey capture, leaves of D. capensis have two types of microscopic glandular trichomes: 'Type 3' trichomes (short, unbranched, biseriate, stalk two- or three-celled, gland vertically divided) and 'Type 10' trichomes (unbranched short glandular hairs, stalk biseriate, gland multicellular).

Like all sundews, D. capensis attracts, captures and digests prey by means of stalked glandular trichomes ('hairs' or 'tentacles') that secrete droplets of sticky mucilage containing digestive enzymes. When a potential prey item contacts the marginal tentacles, they bend toward the centre of the leaf, bringing the prey item into contact with more tentacles. Adjacent marginal tentacles also move toward the prey, making it more difficult for the prey to escape and facilitating digestion. D. capensis is among the sundew species in which the lamina itself also exhibits significant movement. When prey is detected, the leaf blade will slowly bend inwards around the location of the prey, enfolding it. In D. capensis the leaf can bend through more than 180 degrees, 'rolling' around the prey. The extent to which the leaf bends depends on the location of the prey; the closer the prey to the tip of the leaf, the more pronounced the bending response. Experiments involving treatment of leaves of D. capensis with an auxin (indole-3-acetic acid, IAA) and an auxin transport inhibitor (2,3,5-triiodobenzoic acid, TIBA) demonstrated that bending of the leaf is caused by a hormonal growth stimulus transported from the tip of the leaf to the bending point, and induced by a signal originating at the location of the prey.

The mucilage produced by the glandular tentacles of D. capensis is a ~4% aqueous solution of an acidic polysaccharide containing xylose, mannose, galactose, glucuronic acid and an ester sulphate in the ratio 1:6:6:6:1, with a pH of 5. It is viscous—approximately six times more viscous than water at —and so sticky that when fresh it can form threads up to long.

The plant produces one, two or occasionally three inflorescences, The pedicels are semi-erect and long. Sepals are obovate, long and wide, and usually green. Petals are also obovate, long and wide and typically pale purple, sometimes with a darker purple base. Forms with dark purple or white petals also exist. There are five stamens, long with a pink filament and yellow anthers and pollen. The apex of the filament is expanded between the anthers. The ovary is green, obovoid, long and in diameter. The three purple styles are long, forked at the base and lie sub-horizontal, expanding into stigmas that are cylindrical to irregularly obovate. The flowers are self-fertile and autogamous (self-pollinating). Copious seeds are produced in dehiscent capsules, ripening 4–5 weeks after pollination. The seeds are dark brown, shiny, cylindrical with tapered ends, approximately long and in diameter. The testa is deeply ridged longitudinally, with slightly shallower transverse ridges forming a net-patterned (reticulate) surface.

Sundews produce a range of bioactive compounds, including naphthoquinones, flavonoids and their glycosides, and other secondary metabolites. D. capensis contains the naphthoquinone ramentaceone (7-methyljuglone) and trace amounts of plumbagin (its isomer). These compounds have antifeedant, allelopathic and antimicrobial properties and are believed to play a defensive role in plants. They are also of interest for their potential medical uses, including antibacterial and anti-cancer applications. D. capensis contains the flavonoids myricetin and quercetin, which are also of pharmacological interest. The species has been the subject of studies aiming to increase the biosynthesis of its naphthoquinones and flavonoids by applying elicitors including jasmonates and Agrobacterium rhizogenes, and in cell culture by inducing callus formation.

D. capensis is a tetraploid species with a chromosome number of 2n=40. The red-leaved form of the species was the first sundew—and the first carnivorous plant from order Caryophyllales, which also includes Nepenthes, Aldrovanda, Drosophyllum and Dionaea—to undergo whole-genome sequencing. The genome spans a total of 264 Mbp.

, Cederberg, South Africa]] The native range of D. capensis spans the full width of the south coast of the Western Cape province, extending north from Cape Town to Gifberg and eastward into the Eastern Cape as far as Port Elizabeth. Despite its reputation as a weed in cultivation, D. capensis is often uncommon or localised in its native habitat, although it may become locally numerous where competing vegetation is suppressed, such as following a fire.

===Botanical history===

, 1739]] D. capensis was first introduced to Western botany around the end of the 17th century. Paul Hermann became one of the first botanists to collect herbarium specimens of plants from the Cape of Good Hope during his voyage to Ceylon in April 1672, but his plan for a detailed publication on African plants was not fulfilled prior to his death in 1695 A plant that could be D. capensis is listed among the four types of Ros Solis (sundew) in this work, described as Ros Solis Africanus, folio lato, & longo (African sundew, broad and long leaf). The third volume of John Ray's Historia Plantarum, published in 1704, included descriptions of three African Ros Solis, which were attributed to William Sherard. Among these is Ros Solis Africanus, foliis praelongis, caule nudo altissimo (African sundew, very long leaves, very tall bare stem)."."}}

Drosera capensis was one of the five species of Drosera included in Carl Linnaeus' 1753 Species Plantarum, where he gave the short description "" and the origin "". Linnaeus cited as synonymous with D. capensis, the three earlier descriptions noted above. , 1757]] In 1757, John Hill gave a lengthy description of the species in English in the illustrated work Eden, or a compleat body of gardening. Hill did not use Linnaeus' binomial name, giving only the title "African Drosera", but the introduction makes clear which species is referred to: calls it, and , .—, who has adopted for the Genus the Name Drosera, adds as the Distinction of this Species, Lanceolate leav'd Drosera, with the Flower-stalk naked from the Root. It is not unlike in the general Form to the Sundews of Europe; but larger, and more conspicuous than them all; and of a finer Colour.}} Hill included cultivation details, noting that "Mr. Sherrard from Seeds pick out of the Heads of Specimens, of the Plant from the Cape, raised several promising Roots upon a Bog" and that the plant could be grown alongside Sarracenia.—appears alongside another carnivorous plant, Nepenthes. There is no indication that Hill was aware of this shared characteristic, and he surmises (incorrectly) that both plants' fluid secretions serve to "discharge redundant Moisture". it was also the only Drosera included in Bergius' 1767 Descriptiones plantarum ex Capite Bonae Spei. In 1797 Thunberg published Dissertatio botanica de Drosera (defended by his student Daniel Haij) which gave a structured treatment of the ten species then included within genus Drosera. Section 5 of this work () provided an infrageneric arrangement of Drosera based on characteristics of the inflorescence, in which D. capensis was placed within the group Scapigerae (scape-bearing) along with D. cuneifolia, D. rotundifolia and D. longifolia. The distribution was given as "rarer in the mountains"."}}

Thunberg's 1823 Flora capensis included Drosera capensis among five species of South African Drosera, giving details of the flowering period (September to November). In 1824 Augustin Pyramus de Candolle provided the first systematic revision of genus Drosera in his Prodromus systematis naturalis regni vegetabilis, with an infrageneric classification of 32 species into two sections, each having two series. De Candolle placed D. capensis in sect. Rorella ser. Acaules, foliis radicalibus saepius rosulatis (Stemless, with radical leaves often rosulate). In 1848 Jules Emile Planchon published a new treatment of Drosera in the Annales des sciences naturelles. Botanique. This covered 88 species arranged into 13 sections based on morphological characteristics including style division. D. capensis was placed in section Rossolis, which was characterised by a hypogynous flower with five stamens; three styles, bifurcated from the base, with a club-shaped, undivided or bi-lobed apex of the stigma; and three pluriovate placentas. Otto Wilhelm Sonder provided a botanical description of the species in English in the 1859 Flora capensis produced with William Henry Harvey. This included more specific location details—"Wet places, in subalpine situations, near Capetown: Dutoit's-kloof; Paarlberg, and Tulbagh &c." illustrated in La Belgique Horticole, 1880]] Messrs. Veitch presented the plant to the Royal Botanic Society in London on 22 April 1874, and also introduced it to the Royal Botanic Gardens, Kew."}}}} In 1880, the same journal published an illustrated note on D. capensis and D. spatulata by Édouard Morren, recommending these Drosera species as "among the most interesting and easiest to cultivate"."}} The note provided detailed cultivation information, including observations that the plants require pure water and are calcifuges."}} The illustrations were based on plants grown in greenhouses where they had "thrived for several years, multiplying, and flowering regularly"."}} Morren described cultivation of the plants in the coolest part of a hothouse, where they were watered via drops of condensation from the roof."}} , 1881]] The plant was illustrated by Matilda Smith in Curtis's Botanical Magazine in 1881, along with a description by Joseph Dalton Hooker noting that it had flowered in July in a cool greenhouse at Kew. In Carl Georg Oscar Drude's 1888 treatment of Droseraceae, D. capensis was given as one of the example species within subg. Ros-solis section Vagae.

In 1906, the first true monograph of Droseraceae was published in Das Pflanzenreich by German botanist and collector Ludwig Diels. Diels built on Planchon's earlier infrageneric classification and placed D. capensis within subg. Rorella, section Rossolis, series Eurossolis. Diels' monograph was still considered the standard reference for Drosera anatomy and morphology more than a century later. It included detailed commentary and illustrations on germination in D. capensis.

Since 2019, D. capensis has been placed within Drosera sect. Ptycnostigma, under the expanded definition established by Fleischmann et al. based on phylogenetic data. This section contains all African sundews except D. regia and D. indica.

D. capensis is one of the most widely cultivated sundews.

The plant requires warm-temperate conditions and is often grown as a houseplant (on a windowsill or in a terrarium), in a greenhouse, or outside in areas with suitable climate. It can withstand infrequent, short-term exposure to temperatures below freezing; the plant may die back above ground, and re-grow from the roots when warmth returns. It prefers full sun but will tolerate partial shade, and requires permanently moist or wet conditions so is typically grown in a saucer or tray of rainwater. Growing media is often peat-based—for example a mixture of peat and sand or perlite—or live Sphagnum moss.

====Sexual==== D. capensis is readily propagated by seed. The plant is self-fertile and produces hundreds of tiny seeds, which germinate readily on a moist substrate. In favourable growing conditions seedlings can grow to flowering maturity in a single year.

The species can be propagated vegetatively via leaf or root cuttings. Whole leaves can be placed on a moist substrate and will develop plantlets as the original leaf dies; alternatively the entire above-surface part of the plant can be removed and replanted, and will often develop new roots, while the original roots form a new growing point. Short (1.5–3 cm) sections of root from a healthy plant can be taken as cuttings and replanted, forming new buds in 2–6 weeks.

The species has few pests in cultivation, but can be affected by caterpillars and by aphids, which attack the flower stalks.

The following cultivars of Drosera capensis are listed by the International Carnivorous Plant Society, which is the International Cultivar Registration Authority for carnivorous plants: {| border="2" class="wikitable" |+ Cultivars of Drosera capensis ! Cultivar !! Description |- |Drosera 'Albino' Hort. Borret & Farrow |White flowers, lack of red colouration in the leaves and tentacles |- |Drosera 'Narrow Leaf' Hort. D'Amato |Similar to "typical form" but with narrow lamina and petiole, and more compact, rarely producing a tall stem |} Drosera 'Albino' and Drosera 'Narrow Leaf' have both received the Award of Garden Merit from the Royal Horticultural Society. The following Drosera hybrid cultivars with D. capensis involvement are listed by the ICPS: {| border="2" class="wikitable" |+ Hybrid cultivars involving Drosera capensis ! Cultivar !! Parentage !! Description |- |Drosera 'Anemone' Hort. H.Carlton |D. oblanceolata × spatulata × capensis |Stout rosetted plant with elongate leaves intermediate between 'paddle-shaped' and 'strap-shaped'; very tall inflorescence with pale pink flowers |- |Drosera 'Hercules' Hort. C.Trexler |D. capensis × aliciae |Similar in habit to D. capensis but with strikingly broadened leaves that barely reflex, and a tendency to form clumps |}

, Drosera capensis does not have an assessment on the IUCN Red List. On the South African National Biodiversity Institute's Red List of South African Plants it is listed as 'Least Concern', a categorisation applied automatically because it was not highlighted in screening processes used to select taxa of potential conservation concern for detailed assessment. In 2020, as part of a large-scale conservation status assessment of carnivorous plants, it was assessed using IUCN criteria as 'Least Concern'.

Drosera capensis has been deliberately introduced to wetland habitat in numerous countries outside its native range, including New Zealand, the United States, Japan, Australia, Brazil and the Azores. Many of these locations are ecologically sensitive, and introduced species such as D. capensis may compete with threatened local flora. It has become established in the Waitākere Ranges, either due to deliberate planting or via soil contamination from other introduced plants. Its seeds are believed to be distributed by waterfowl. The species is subject to 'sustained control' under the Conservation Auckland Regional Pest Management Plan. In Mendocino County California, Albion Bog—a raised bog in rare dwarf forest habitat—has become infested with non-native carnivorous plants as a result of deliberate plantings by enthusiasts from the 1960s onwards. Drosera capensis has formed dense stands, outcompeting the native sundew D. rotundifolia, and conservationists have found it impossible to eradicate. In Australia, D. capensis was reported as naturalised at a single site in the Royal National Park, where at least 100 adult plants were observed. In Hawaiʻi, although not known to be naturalised, it is assessed as a 'high risk' species by the Plant Pono initiative due to characteristics including its self-fertility; prolific seed production; capacity for hybridisation; rapid growth to maturity; tolerance of a wide range of growing conditions; and ability to regenerate after frost and fire damage. The species is listed (with a 'low' risk rating) in A Global Compendium of Weeds.