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Calodendrum capense
Calodendrum capense
Calodendrum capense
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Cape chestnut
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Rutaceae
Genus: Calodendrum
Species:
C. capense
Binomial name
Calodendrum capense

Calodendrum capense, the Cape chestnut, is an African tree which was first studied at The Cape in South Africa and cultivated widely for its prolific flower display. The tree obtained the common name of "Cape chestnut" because explorer William Burchell saw a resemblance to the horse chestnut in terms of flowers and fruit, though the two are not closely related.

Range

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It is native to a swath of the east side of the continent from the equatorial highlands of Kenya at its northern limit southwards through isolated mountains in Tanzania to both sides of Lake Malawi, the Mashonaland Plateau and Eastern Highlands of Zimbabwe, and then along the lower slopes of the Drakensberg Mountains of South Africa and in coastal forests from Gqeberha to Cape Town.

Habit

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The tree can reach 20 metres high in a forest, but in cultivation it is more likely to reach 10 metres, with a spreading canopy.

Bark and flowers

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The trunk is smooth and grey and the leaves are ovate up to 22 cm long and 10 cm wide. The large pink flowers are produced in terminal panicles and cover the tree canopy in the early summer.

Uses

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Cape chestnut oil, obtained from the seeds, otherwise known as Yangu oil, is a popular oil in African skin care. Its inherent ultraviolet protection, its high content of essential fatty acids and antioxidants and its mild odour destined it for natural cosmetics. The seeds are eaten by birds and monkeys.

[edit]
  • Bark texture
    Bark texture
  • Secretory cavities in leaf
    Secretory cavities in leaf
  • flowers
    flowers
  • green fruit capsule
    green fruit capsule
  • dry fruit capsules
    dry fruit capsules
  • Seeds
    Seeds

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Calodendrum capense

View on Grokipedia
from Grokipedia
Calodendrum capense, commonly known as the Cape chestnut or wild chestnut, is a to in the family , native to seasonally dry tropical biomes across eastern and . It typically reaches heights of 5–20 meters with a rounded, dense canopy, featuring smooth grey bark, opposite aromatic leaves up to 14 cm long, showy terminal sprays of pink to mauve flowers, and distinctive warty, five-lobed capsules containing black oily seeds. This slow-growing species is valued for its ornamental qualities, timber, and seed oil, which is extracted for use in soaps, , and skincare products. The tree's native range extends from and in the north through , , , and to and in the south, often found in evergreen riverine forests, wooded ravines, and coastal scrub at altitudes from to 2,200 meters. It thrives in a variety of soils, including those with poor drainage, and demonstrates tolerance to , light down to -5°C, and occasional waterlogging, making it adaptable to both coastal and inland environments. Ecologically, C. capense supports by attracting bees, , and birds with its nectar-rich blooms and fruit, while its non-aggressive root system suits it for applications such as shade provision in plantations and windbreaks. In addition to its ecological role, Calodendrum capense has significant economic and cultural value; its hard, durable wood (density 700–800 kg/m³) is used for furniture, tool handles, and , while the seed oil serves as an emollient in and modern skincare. Widely propagated from seeds and cultivated as a , , or specimen in subtropical regions, it is considered of least concern by conservation assessments due to its broad distribution and lack of major threats.

Taxonomy

Classification

Calodendrum capense belongs to the kingdom Plantae, phylum Tracheophyta, class Magnoliopsida, order , family (subfamily Zanthoxyloideae, tribe Diosmeae), commonly known as the citrus or rue family. This placement aligns it with other economically important plants like species, sharing characteristics such as glandular leaves and fruits. The genus Calodendrum Thunb. comprises two accepted species, C. capense and C. eickii Engl., both native to . Calodendrum capense (L.f.) Thunb. is the of the , established by in his Nova Genera Plantarum in 1782. The , Dictamnus capensis L.f., was originally described by (Linnaeus filius) in Supplementum Plantarum in 1781, based on specimens from the . Thunberg transferred it to the new Calodendrum upon recognizing its distinct morphological features, such as its showy inflorescences. Limited synonyms exist for C. capense, including Dictamnus calodendrum Poir. from 1812.

Etymology

The genus name Calodendrum is derived from the words kalos, meaning "beautiful," and dendron, meaning "," in reference to the plant's attractive flowers. The specific epithet capense is the Latinized form of "," denoting the species' origin in the Cape region of , where it was first collected. The common name "Cape chestnut" was coined by the British explorer and naturalist William Burchell (1781–1863) during his travels in in the early , owing to the superficial resemblance of the tree's flowers and fruits to those of the unrelated horse chestnut (). The binomial name Calodendrum capense was formally established in the late amid European botanical explorations of ; it was first described by and published by Carl Thunberg in 1782.

Description

Habit and growth

Calodendrum capense is a medium-sized characterized by an upright trunk and lateral branches that form a broad, rounded crown. In natural settings, it attains a mature height of 5 to 20 meters, while in open areas or at forest margins, it typically reaches about 7 meters with a more spreading form. In cultivation, the tree generally grows to 6 to 10 meters tall, developing a dense canopy that can spread up to 10 to 15 meters wide when fully leafed. The growth habit varies by environmental conditions: it remains in coastal regions but becomes or fully in higher elevations or drier inland areas. The tree exhibits a slow to moderate growth rate, with annual height increases of up to 1 meter under optimal conditions such as warm temperatures and high rainfall. Branching occurs with several major limbs spaced along the central trunk, contributing to the overall stability and expansive structure. Calodendrum capense is long-lived, with individuals capable of surviving for many decades, as evidenced by specimens estimated at over 90 years old. This , combined with its moderate growth, makes it a suitable choice for long-term planting.

Bark and trunk

The trunk of Calodendrum capense is usually single-stemmed and straight in habitats, often developing buttresses at the base in mature specimens, while trees in open or dry areas tend to be more branched and gnarled from a younger age. The bark is smooth and light to medium across all ages, occasionally appearing mottled or streaky with coverage in older trees, though it darkens to a deeper in hot, dry environments. This smooth bark texture contributes to the tree's ornamental appeal, and its non-aggressive makes C. capense suitable for planting in urban settings such as streets and areas without risk of structural damage. The wood features a white to light yellow heartwood, sometimes marked with brown streaks, and is characterized by straight , moderate , , and of 700–800 kg/m³ at 12% content; it exhibits good bending properties but limited natural , being susceptible to and Lyctus attack. Due to these traits, the timber sees limited commercial exploitation but is valued locally for durable applications like tent bows, wagon yokes, planking, shovel handles, and furniture.

Leaves

The leaves of Calodendrum capense are arranged oppositely along the branches, a characteristic feature of the family. They are simple, lacking the compound structure typical of many relatives in the family, and elliptic to ovate in shape with undulate, entire margins. Each leaf blade measures 6–18 cm in length and 3.5–11 cm in width, glossy dark green on the upper surface and paler green beneath, contributing to the tree's dense, shimmering canopy. The petiole is short, 2–10 mm long, and the leaves are pinnately veined with up to 20 pairs of lateral veins prominent on the underside. Translucent oil glands dot the blade, visible against the light, which is a hallmark of the genus. These glands produce essential oils responsible for the aromatic scent released when leaves are crushed. In humid coastal habitats, the leaves are evergreen, retained year-round to maintain canopy density. In drier inland areas, the tree is semi-deciduous, shedding most leaves seasonally and remaining bare for several months before new growth emerges. Young leaves initially display a bronze-coppery tint, maturing to bright green.

Flowers and inflorescence

The of Calodendrum capense consists of terminal panicles, typically 15-20 cm long, that are densely flowered and arise from the ends of branches. These panicles are upright and conspicuous, often extending above the foliage to create a striking display. Individual flowers measure 4-6 cm in diameter and feature five free, narrow petals that are to or occasionally , with a crinkled, crepe-paper-like texture. The flowers also include numerous fertile stamens bearing anthers, along with five petal-like staminodes that are and dotted with , and a superior . Blooming occurs primarily in early summer, from October to December in the southern hemisphere, with the flowering lasting 4-6 weeks per tree and exhibiting high synchrony that covers much of the canopy. The flowers emit a faint, sweet, citrus-like fragrance that enhances their ornamental appeal. They produce abundant nectar and pollen, which support visitation by bees and butterflies.

Fruit and seeds

The fruit of Calodendrum capense develops from the multi-carpellate of the flower, which is elevated on a prominent gynophore, forming a woody, dehiscent capsule that measures 3–6 cm in diameter and features a knobby, rough surface with 5 distinct valves or lobes. The capsule is initially bright green and smooth, maturing to a color as it dries and splits open along the valves to release the seeds. Fruits typically ripen about 3 months after flowering, though they may persist on the tree for several additional months post-dehiscence due to their woody structure. Each capsule contains 1–5 seeds, which are large, black, shiny, and angled or pyramid-shaped, measuring 1–1.5 cm in length or diameter. The seeds are notably oily, with an oil content of approximately 60% by weight in the kernel, making them a rich source of . This is yellowish and bitter, composed primarily of unsaturated fatty acids, including (33–44%) and (26–37%), alongside saturated components like (18–24%) and (about 5%). In traditional practices, the has been extracted for applications in and as a due to its emollient properties. Seed viability is maintained for up to 1 year under dry storage conditions, provided they are protected from insect damage, after which rates decline significantly.

Distribution and habitat

Geographic range

Calodendrum capense is native to eastern and southern Africa, with its range extending from the highlands of and southward through and to South Africa's and provinces. This distribution follows a corridor along the eastern seaboard and associated uplands, encompassing countries such as , , and . The species occurs across a broad elevational gradient, from in southern African coastal forests and scrub to altitudes of up to 2,300 meters in East African montane and riverine forests. Despite its wide span, which covers approximately 3,000 kilometers latitudinally from northern to the Cape region, C. capense is absent from the central African Congo Basin and western arid zones of the continent, such as and , where suitable moist forest habitats are lacking. It was first documented in 18th-century botanical collections from the by , who described the species in 1782. Beyond its native range, Calodendrum capense has been introduced and cultivated in subtropical regions worldwide, including , , and parts of Mediterranean , where it is valued ornamentally.

Preferred habitats

Calodendrum capense thrives in subtropical to temperate climates across eastern and southern Africa, where it experiences mean annual rainfall ranging from 800 to 1,500 mm, though it can tolerate 600 to 2,000 mm. The species is sensitive to , withstanding temperatures down to -5°C but suffering damage below this threshold, particularly in its juvenile stages. It occurs from sea level to altitudes of 2,300 m, favoring warm, sunny positions with daytime temperatures between 15°C and 45°C. The tree prefers well-drained, deep, fertile, and moist soils, such as loamy forest soils or black cotton soils, and tolerates poorer fertility and drier conditions. It performs best in slightly acidic to neutral levels (5.5–7), avoiding waterlogged sites. C. capense is versatile in , adapting to sandy loams in coastal areas and heavier clays inland, provided drainage is adequate. In natural settings, Calodendrum capense inhabits coastal and lowland forests, riverine thickets, wooded ravines, fringe forests, and montane woodlands, often within semi- associations. It occasionally appears in scrublands but is most abundant in mistbelt and higher-altitude forests. Common associates include Podocarpus falcatus and in mistbelt forests, as well as species like in drier woodland margins and in transitional zones near the . The species demonstrates adaptations such as habit in seasonal, drought-prone interiors to conserve water, while remaining along humid coasts; it also exhibits moderate salt tolerance in coastal ecosystems.

Ecology

Pollination and reproduction

Calodendrum capense exhibits primarily entomophilous , with flowers attracting a range of including honeybees (Apis mellifera) and various that visit for and . The flowers produce a minor to medium supply of , which is light yellow and yields dark, strongly flavored , alongside collected as dark grey or orange pellets by foraging bees. While some bird visitation occurs, sources indicate that birds do not typically serve as primary pollinators, with insect activity dominating the process. The breeding system of C. capense is partially self-incompatible, necessitating cross-pollination for successful fruit set and promoting to maintain . Flowering displays enhance attraction through synchrony, with the entire tree canopy bursting into bloom simultaneously during peak periods, creating a prolific floral spectacle that covers the branches in pink or white flowers. This reproductive strategy aligns with the plant's annual cycle, where flowering occurs erratically from July to March but peaks in early summer (October to December), often triggered by seasonal rains in its native habitats. Seed production follows successful pollination, with mature trees yielding numerous woody capsules in good years, each containing several oily black seeds. Fruits ripen approximately three months after flowering, typically from January to May, and contain 600–1,000 seeds per kilogram. Fresh seeds exhibit high viability, with germination rates reaching up to 90% under optimal conditions, occurring within 10–40 days in well-drained, moist soil at temperatures of 25–28°C. This efficient reproductive output supports the species' persistence in forest margins and ravines, though fruit set in natural populations can vary due to pollinator availability and environmental factors.

Wildlife interactions

Calodendrum capense engages in various symbiotic and antagonistic interactions with wildlife, particularly in its native and coastal forest habitats. Seed dispersal occurs primarily through zoochory, where the oily seeds are ingested by birds such as Cape parrots (Poicephalus robustus), rameron pigeons (Columba arquatrix), African olive pigeons (Columba arquatrix), and cinnamon doves (Turtur tympanistria), as well as monkeys including samango (Cercopithecus mitis) and vervet (Chlorocebus pygerythrus) species; these animals consume the seeds and disperse them via droppings, facilitating regeneration over distances. The woody capsules dehisce to release the large, oil-rich seeds, which further attract these dispersers due to their nutritional value. The plant experiences herbivory from multiple taxa, contributing to its ecological dynamics. Leaves serve as a host for larvae of swallowtail butterflies, including the orange dog (), which feed on the foliage and can cause defoliation in outbreaks. Larger herbivores such as (Sylvicapra grimmia) and bushbuck ( sylvaticus) consume the fruits, potentially aiding dispersal while exerting pressure on seed production. Additionally, occasional damage arises from sap-sucking pests like and scale insects, which infest shoots and branches, though these are typically managed in natural settings by predatory . Pollinator interactions favor long-tongued insects, with butterflies and bees accessing the nectar-rich flowers, promoting cross-pollination and supporting local insect biodiversity. The nectar provisions benefit pollinator populations, enhancing forest insect diversity. In woodland ecosystems, C. capense plays a supportive role by providing a key food source for seed-eating birds, contributing to avian nutrition and indirectly bolstering forest regeneration through sustained dispersal networks.

Cultivation and uses

Cultivation

Calodendrum capense is primarily propagated by seeds, which should be sown fresh after collection to achieve high germination rates of up to 90% within 10 to 40 days. To test viability, seeds can be soaked in warm water; viable ones sink while infertile ones float. Semi-hardwood cuttings from half-grown shoots, treated with rooting hormone, also succeed, though they root more slowly than seeds. Grafting is possible but rarely practiced due to the tree's ease of propagation by other methods. The tree thrives in full sun to partial shade and prefers well-drained, fertile with a of 5.5 to 7. For use as street trees, with spacing of 8 to 10 meters to accommodate the mature canopy spread of 8 to 12 meters. It adapts to a range of soils, including deep moist loams and drier sites as well as those with poorer drainage, and demonstrates tolerance to occasional waterlogging, though prolonged poor drainage can lead to . Once established, Calodendrum capense needs moderate watering during the first few years, becoming drought-tolerant thereafter with rainfall of 600 to 2,000 mm annually. Prune lightly after flowering to maintain shape and remove dead wood, particularly on young trees to encourage a strong structure. Fertilize annually in spring with a balanced slow-release formula to support vigor and flowering, avoiding excess to prevent overly lush foliage at the expense of blooms. This species is hardy in USDA zones 9 to 11, tolerating brief frosts to -5°C once mature but requiring protection for young plants from temperatures below 20°F. It performs well in coastal urban environments, enduring salt spray if shielded from direct winds, and matches climates similar to its native subtropical range. Calodendrum capense is generally low-maintenance with minimal pest issues, though it can suffer from and collar rot caused by in poorly drained soils, akin to vulnerabilities in related species. Monitor for or scale insects occasionally, but serious infestations are rare in suitable conditions.

Human uses

Calodendrum capense is prized as an ornamental for its striking display of pink to flowers in summer, making it a popular choice for shade, specimen, and street planting in gardens, parks, and urban landscapes since its introduction in the . The durable, straight-grained wood, which is light yellow and moderately heavy, is utilized for furniture, tool handles like shovel and components, wagon-making, planking, and bows, though commercial remains limited due to its semi-protected status in native ranges. Seeds are processed to extract yangu oil, a lemon-yellow liquid high in (33–48%) and tocopherols, which is applied in , soaps, and traditional remedies for moisturizing dry , treating conditions like eczema and , and providing natural UV protection. In indigenous African traditions, the bark—sold in markets as 'white umemezi'—serves as a skin lightener and in , while leaves and other parts function as insecticides; additionally, seeds are attributed symbolic powers in to confer skill and luck to users.

References

  1. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:771766-1/general-information
  2. https://tropical.theferns.info/viewtropical.php?id=Calodendrum+capense
  3. https://apps.worldagroforestry.org/treedb/AFTPDFS/Calodendrum_capense.PDF
  4. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:771766-1
  5. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:331447-2
  6. https://www.ipni.org/n/771766-1
  7. https://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=133080
  8. https://pza.sanbi.org/calodendrum-capense
  9. https://sbbeautiful.org/cape-chestnut-calodendrum-capense/
  10. https://www.smgrowers.com/products/plants/plantdisplay.asp?strLetter=C&plant_id=301
  11. https://prota.prota4u.org/protav8.asp?g=pe&p=Calodendrum+capense
  12. https://hort.ifas.ufl.edu/woody/pages/calcap/calcap.shtml
  13. https://vhd.heritagecouncil.vic.gov.au/places/210468/download-report
  14. https://plantmaster.com/plants/eplant.php?plantnum=25178&project=3711
  15. https://tropical.theferns.info/viewtropical.php?id=Calodendrum%2Bcapense
  16. https://apps.worldagroforestry.org/treedb2/speciesprofile.php?Spid=418
  17. https://treesa.org/calodendrum-capense/
  18. https://cjmgrowers.co.za/calodendrum-capense/
  19. https://naturebackin.com/2020/03/12/the-beautiful-cape-chestnut-host-to-the-citrus-swallowtail-butterfly/
  20. https://sfyl.ifas.ufl.edu/media/sfylifasufledu/miami-dade/documents/landscapes-amp-gardening/African-Ornamentals-for-Miami-Dade.pdf
  21. https://hortflora.rbg.vic.gov.au/taxon/ada605b6-5340-11e7-b82b-005056b0018f
  22. https://prota.prota4u.org/protav8.asp?g=pe&p=Calodendrum%2Bcapense
  23. https://www.worldfloraonline.org/taxon/wfo-0000580859
  24. http://erepository.uonbi.ac.ke/handle/11295/36728
  25. https://prota.prota4u.org/protav8.asp?g=pe&p=Calodendrum%20capense
  26. https://www.sohosandiego.org/presidio/calodendrumcapense.htm
  27. https://www.smgrowers.com/products/plants/plantdisplay.asp?strLetter=C&plant_id=301&page=
  28. https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.10564
  29. https://www.dargleconservancy.org.za/forests.php
  30. https://ia600602.us.archive.org/3/items/beeplantsofsouth37mfjo/Strelitzia_37_2016_bw.pdf
  31. https://prota4u.org/protasources?h=Calodendrum%20capense&p=Calodendrum%20capense
  32. https://www.cepf.net/resources/documents/final-report-appendix-3
  33. https://www.picturethisai.com/flower-problems/Calodendrum_capense.html
  34. https://apps.worldagroforestry.org/usefultrees/pdflib/Calodendrum_capense_KEN.pdf
  35. https://www.gardensonline.com.au/gardenshed/plantfinder/show_1433.aspx
  36. https://streetsla.lacity.org/bss-ufd-street-tree-selection-guide
  37. https://myplantin.com/plant/3015
  38. https://www.picturethisai.com/care/Calodendrum_capense.html
  39. https://www.desert-tropicals.com/Plants/Rutaceae/Calodendrum_capense.html
  40. https://www.gardeninginsouthafrica.co.za/trees/wild-chestnut-wildekastaiing-umbhaba-umemezi-umsitshana-umbaba-umemezi-omhlophe-molalakgwedi-mookelela-muvhaha-calodendrum-capense
  41. https://www.natureinbottle.com/product/yangu_cape_chestnut_oil
  42. https://www.cabidigitallibrary.org/doi/10.5555/20240352300
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