Ricinodendron heudelotii
| Njangsa (Ricinodendron heudelotii) | |
|---|---|
| |
| Scientific name | Ricinodendron heudelotii |
| Family | Euphorbiaceae |
| Order | Malpighiales |
| Genus | Ricinodendron |
| Common names | Njangsa, ndjanssang, essang, akpi, African oil-nut tree |
| Native range | Tropical Africa: Senegal east to Kenya, south to Angola and Mozambique |
| Edible parts | Kernels; young leaves cooked as a vegetable |
| Years to fruit | 7-10 years from seed; about 3-4 years reported in managed plantations |
Njangsa (Ricinodendron heudelotii), also written ndjanssang and traded as essang or akpi, is a large, fast-growing, deciduous tree of the spurge family and the single widely accepted species of the genus Ricinodendron.[1][2][3] It occurs across the wet lowlands of tropical Africa, where its oil-rich kernels are a traditional cooking ingredient, flavoring and soup thickener.[4]
Description[edit | edit source]
Across its range the tree is light-demanding and typical of forest clearings, moist semi-deciduous and secondary forest, riverain forest and abandoned farmland.[5][4] Trees commonly stand 20-30 m tall, with reports to 30-45 m and exceptional records near 50 m; the bole reaches about 120-150 cm in diameter, mature trees develop buttresses, and some accounts describe long running surface roots.[4][6][7]
Growth can be rapid: seven-month-old nursery seedlings averaged about 0.90 m tall with taproots about 0.65 m long, and young homegarden trees in the same Cameroon study reached roughly 3.5 m at 2.5 years and about 17.5 m at 5 years.[8] Branchlets are densely brown-hairy when young.[6] Juvenile leaves are simple, alternate and trilobate; mature leaves are palmately compound with three to five sessile, acuminate leaflets, about 10-15 cm long in one account and up to 10-40 cm long by 6-15 cm wide in another.[9][6] Older trunks carry thick, cracked bark.[9]
Flowers are yellowish white, about 4-5 mm across, borne in panicles that reach about 40 cm in males; female panicles are shorter and stouter.[6][7] Male plants shed their leaves more completely than females.[9] The fruit is an indehiscent drupe with two or three lobes, about 2.5-3.5 by 4-5 cm, with a thick hard shell and, at maturity, a smell of overripe apples; dried fruits in the subspecies accounts measure 1.3-3.5 cm across.[4][7][5] Each lobe holds a one-seeded stone with a rounded, flat, hard-shelled seed, reddish-brown to black, roughly 1-1.5 cm across and sinuously ridged in an Ivorian account; seeds number about 5,200 per kilogram.[6][7][9][4] Ripe-fruit color is reported differently: one monograph describes fruits green when young and black when ripe, while an Ivorian account describes yellow or yellow-green drupes at maturity.[4][9]
Subsp. heudelotii occupies the western range from Senegal to Benin, with mostly three-lobed fruits; subsp. africanum runs from Nigeria eastwards and southwards, where two-lobed fruits are more common, and the two differ in locule and style number of the female flowers.[4][5] Some accounts write the eastern taxon at variety rank, and one encyclopedia treatment lists a Kenya-Tanzania variety tomentellum.[7][3]
Cultivation[edit | edit source]
Most accounts place the species in the wet lowlands: elevations of roughly 200-500 m in one monograph and 100-1250 m in broader accounts, minimum annual rainfall near 1,000 mm with a typical 1,400-3,500 mm in the core range and up to 10,000 mm reported in Cameroon, and mean annual temperatures of about 18-32 C.[4][7][3]
Soil and water[edit | edit source]
The soil preference is consistent across the monographic accounts: medium-textured, freely draining acid soils, with lowland oxisols and ultisols at pH near 5-6 listed in one account.[4][7][3] In humid forest soil, seedlings respond to supplemental nutrition: in a Cameroon pot trial, combined compost and NPK gave the highest seedling biomass and significantly increased leaf area, and the authors recommended applying the combination at about 3, 6 and 15 weeks after potting.[10]
Sun and humidity[edit | edit source]
The species is a heliophyte, described in one Cameroon seedling study as needing no shading where preserved on farmland.[10] It belongs to the wet tropical biome, and the humid, warm conditions of that zone suit it; mean annual temperatures across the range are about 18-32 C.[2][4][7]
Seasonal changes[edit | edit source]
The tree is deciduous: it stands leafless for a few weeks while its fruits fall, and male plants lose their leaves more completely than females.[4][7][9] In Sierra Leone, flowering runs April-May with fruits maturing September-October; in Cameroon, peak flowering falls around March at the end of the dry season and lasts two to three months, with the main fruit season August-December.[6][7][4] Timing shifts with site and year: in the Cameroon study, trees at wetter Sangmelima fruited later but over a shorter span than at Yaoundé, and germplasm harvest there was practical from October to December.[8] Growers in seasonally dry climates can expect the main flowering flush near the end of the dry season, with fruit maturation through the rainy months.[4][6]
Propagation[edit | edit source]
Untreated seeds germinate poorly: in one Cameroon trial they gave no germination at all, the stones are hard and slow to break down, and Cameroon farmers seldom plant the tree because establishment from seed is difficult.[8][5] Hand scarification of the stony endocarp gave about 62% germination in that trial, sulphuric-acid soaking only 0-15%, and hot-water treatment killed embryos or gave essentially no germination.[8][9] Soaking in plain water is gentler: in an Ivorian nursery trial, a 72-hour soak worked best for sowing in plastic bags and a 96-hour soak best on plank ridges, with germination delays of 12-21 days in bags and 19-29 days on ridges.[9] A Ghana trial found that burning about 5 kg of dry grass on the seeds raised germination to 69%, and up to 79% for seed from a favored source; that report recommends soaking seed about 21 days in water and then burning 5 kg of grass at 15% moisture content on the seeds, and another account gives the best medium as a 1:3 mixture of river sand and forest soil.[11][3]
Seeds are liable to insect attack in storage; mixing in ash before cool, dry storage reduces damage.[7] Seedlings give no clue to sex, so a nursery batch cannot be preselected for fruiting females.[4][6]
Vegetative routes are used because seed germination and seedling sex are unreliable; the PROTA monograph lists leafy stem cuttings, layering and side grafting.[4] Leafy cuttings in non-mist propagators can exceed 80% rooting: take young, vertical, non-woody shoots, cut them to 3-5 cm keeping one node with two leaves and about 8 cm2 of leaf, set them in a sawdust medium, and rooting begins after about two weeks; rooting hormone increases root number.[6] In open-field trials without such protection, sprouting from 30 cm cuttings 2-4 cm thick was only 4-17%, with no significant difference between vertical and slanting orientation.[8]
For field establishment, plants are set in cleared sites at about 10 m spacing after at least six months under shade and a minimal height of 20-30 cm; a palm-frond shade fence for the first two weeks, abundant watering, mulching and weeding while young help the transplant establish.[3]
Flowering, fruiting, and harvest[edit | edit source]
The species is dioecious: only female trees bear fruit, and the proportion of fruiting trees varies by site, from 60% at Yaoundé to 35% at Sangmelima in the Cameroon study.[8] First bearing comes late: about 8-10 years in one monograph and in the 7th to 10th year for trees in open light in another account, while a compiled account adds 6-7 years in forests and about 3-4 years in managed plantations.[4][7][3] Individual tree yields vary widely: a project factsheet reports up to 4,000 fruits in a year, while a compiled account describes bearing every two to three years with up to about 900 fruits and an average of 72 kg of kernels per harvest.[6][3]
Ripe fruits fall naturally and harvest is from the ground. Fruits are heaped under the tree for two to four weeks until the pulp rots, then washed and boiled so the shells crack; the stones are opened by hand with a knife or nails, and the kernels are sun- or fire-dried.[4][9][3] Well-dried kernels can be stored up to about two years, and ash added before storage reduces insect damage.[3][7] Ground-picking follows the local fruit fall, September-October in Sierra Leone and from October to December in the Cameroon forest zone.[4][8]
Fruit and uses[edit | edit source]
The marketed food is the kernel, not the whole fruit. Kernels are eaten boiled or roasted, ground into sauces and pastes (akpi sauce in Côte d'Ivoire, roasted paste in Gabon), pressed for cooking oil and used to thicken soups and stews; dried, pounded kernels are stored for porridge in food shortages.[4][7][9][6] The protein-rich leaves are cooked as a vegetable, and the seed product is not valued as food in every part of the range.[4]
Composition varies with provenance and method. One compiled table gives per 100 g of dried kernels about 21 g protein, 43 g fat (up to about 60% in some accounts), 23 g carbohydrate, 611 mg calcium, 926 mg phosphorus and about 530 kcal; the Agroforestree profile lists kernel oil near 47% of weight, with eleostearic acid about 44%, oleic about 16% and roughly 10% each of palmitic, stearic, linoleic and linolenic acids.[4][7] A 2014 laboratory analysis of dried Cameroon seed meal found 31.4% crude protein and 44.7% lipid, about 74% of the lipid polyunsaturated with notable long-chain omega-3 fatty acids, while alpha-eleostearic acid is placed at 30-51% of the oil in the monograph account.[12][4]
Kernels are a traditional staple eaten after boiling or other processing, and that processed form is the basis of kitchen use across the region. One account repeats an older statement of no known toxicity, while another records unnamed traces of an alkaloid and resin in the seed.[8][12]
Intercropping and agroforestry[edit | edit source]
The tree is retained in traditional agroforestry, intercropped with coffee, cocoa or bananas and used as shade for cacao.[7] In a five-locality survey of producing cacao farms in western and southwestern Côte d'Ivoire, farms retaining R. heudelotii showed lower cacao pod-rot rates and higher cacao biomass and carbon storage, with no measured effect of the 10-20 m distance on cacao vigor or yield; being observational, those associations do not prove causation.[13]
Pests and other problems[edit | edit source]
Young plants are the main target of pests. In Cameroon, a psyllid (Diclidophlebia xuani) and aphids can seriously damage young trees; aphids curl nursery leaves and can be controlled with systemic insecticide, with no further treatment usually needed after the plants gain vigor about two years in the field.[4][3] Project guidance for young trees emphasizes protection against weevils and borers.[6]
Photos[edit | edit source]
References[edit | edit source]
- ↑ [3] Njangsa – Wikipedia.
- ↑ [5] Plenderleith, Ricinodendron heudelotii: A State of Knowledge Study for CARPE (Oxford Forestry Institute).
- ↑ [8] Domestication of Ricinodendron heudelotti (Baill.) Pierre Ex. Pax. in the humid lowlands of Cameroon (Global Journal Series, AJOL).
- ↑ [9] Kouamé, Gnahoua & Mangara 2012, Essais de germination de Ricinodendron heudelotii (Euphorbiaceae) dans la région du fromager au centre-ouest de la Côte d'Ivoire, Journal of Applied Biosciences 56: 4133-4141.
- ↑ [10] Anjah, Tabi & Mvondo Ze 2015, Effect of organic and inorganic fertilizers on regeneration of seedlings of Ricinodendron heudelotii, International Journal of Biological and Chemical Sciences 9(3): 1289-1298.
- ↑ [11] Nkyi 2012, Effects of source, water conditioning and thermal treatment on germination of Ricinodendron heudelotii seeds, Journal of Applied Science and Technology 17(1/2): 114-120 (abstract).
- ↑ [12] Ezekwe, Besong & Johnson 2014, Nutritive composition of omega-3 fatty acids-rich Ricinodendron heudelotii, International Journal of Nutrition and Metabolism 6(6): 56-62.
- ↑ [13] N'Zi et al. 2022, Analysis of the Ricinodendron heudelotii x Theobroma cacao L. Interaction in Traditional Agroforestry Systems in Côte d'Ivoire, Horticulturae 9(1): 26.
Image credits[edit | edit source]
- Njansang.jpg – Dried Ricinodendron heudelotii kernels (njansang) for sale in Central Africa. Creator: Laurie E. Clark and Terry C. H. Sunderland. License: Public domain (US Government work; USAID report "The Key Non-Timber Forest Products of Central Africa: State of the Knowledge"). File page.
- Ricinodendron heudelotii trunk.jpg – Trunk of a Ricinodendron heudelotii tree, Central Africa. Creator: Laurie E. Clark and Terry C. H. Sunderland. License: Public domain (US Government work; USAID report "The Key Non-Timber Forest Products of Central Africa: State of the Knowledge"). File page.
