Trachypogon spicatus (PROTA)

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Plant Resources of Tropical Africa
Introduction
List of species


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Trachypogon spicatus (L.f.) Kuntze


Protologue: Revis. gen. pl. 2: 794 (1891).
Family: Poaceae (Gramineae)
Chromosome number: 2n = 20

Synonyms

  • Trachypogon plumosus (Humb. & Bonpl. ex Willd.) Nees (1829).

Vernacular names

  • Giant spear grass, greybeard grass, spiked crinkleawn, arrow grass (En).

Origin and geographic distribution

Trachypogon spicatus is widely distributed in tropical Africa, from Côte d’Ivoire eastward to Ethiopia and southward to South Africa and Madagascar. It also occurs in the Americas, from the southern United States southward to Paraguay.

Uses

Trachypogon spicatus is used as thatch on houses. It has some suitability for pulping. It is only grazed when it is very young. It tends to form a dense soil cover providing protection against erosion in areas with high rainfall. It is considered a weed of plantations in Tanzania, but it is easy to control.

Production and international trade

Trachypogon spicatus is only used locally.

Properties

The palatability of Trachypogon spicatus is low, except when the foliage is very young. Chemical analysis of fresh material in the early flowering stage in Kenya recorded: crude protein 5.7%, crude fibre 40.2%, ash 9.6%, ether extract 1.8% and nitrogen-free extract 42.7% on a dry matter basis. The root secretes a substance which stimulates germination of the seed of Tagetes minuta L.

Botany

Perennial, tufted grass; stems up to 200 cm tall, bearded at the nodes. Leaves alternate; sheath with auricles at the mouth; ligule membranous, without a hairy fringe; blade filiform to linear, 15–40 cm × 1–7 mm, flat or with margins rolled in. Inflorescence terminal, composed of 1(–5) racemes 4–30 cm long; rachis tough, with linear internodes, glabrous. Spikelets paired, 1 subsessile, 1 pedicelled; subsessile spikelet male or sterile, oblong, 8–13 mm long, dorsally compressed, awnless, narrowly and usually inconspicuously winged on the margins above, persistent on the rachis; pedicelled spikelet 2-flowered, subterete, 8–13 mm long including the white bearded callus 1–3 mm long, pungent, obliquely attached to the internode, lower glume oblong, as long as spikelet, obtuse at the apex, leathery, glabrous or hairy, lower floret sterile, reduced to a hyaline lemma, upper floret bisexual, lemma linear, 0.5 mm long, entire, with a flexuous, pubescent or plumose awn 4–10 cm long, palea absent or minute, lodicules 2, stamens 3, ovary glabrous, stigmas 2. Fruit a rounded caryopsis (grain).

In southern Africa Trachypogon spicatus grows mainly during summer and late summer. Its growth rate is moderate to slow. Flowering in southern Africa is in October–May. The awn twists under the influence of moisture which may aid in burying the seed into the soil. Trachypogon spicatus uses the C4 photosynthetic pathway.

Trachypogon is classified in the Andropogoneae. It comprises 3–5 species and is distributed in tropical Africa (including Madagascar) and tropical America. The genus is unusual in that the sessile spikelet is male or sterile and awnless.

Ecology

Trachypogon spicatus generally occurs in wooded grassland and bushland, sometimes favouring the margins of flood plains and drainage tracts, from sea-level up to 2800 m altitude in equatorial areas and from sea-level up to 1700 m in southern tropical Africa. In South Africa Trachypogon spicatus occurs in the wet, subtropical eastern mountain and Highveld region as well as along the southern to south-western parts at 500–2300 m altitude. Rainfall may be from 600–1500 mm per year. It is a climax species that increases in lightly utilized rangeland. It usually occurs on sandy and gravelly soils, but may also be found near seasonal wetlands. In the Highland Sourveld in South Africa Trachypogon spicatus is characteristic of patches left ungrazed by cattle. In the ungrazed patches, soil moisture and soil depth were higher and the nutrients K and P were lower than in grazed patches, while more palatable grasses dominated in the grazed patches. Regular controlled burning and light grazing increase the proportion of Trachypogon spicatus in the vegetation, as it also increases more palatable species such as Themeda triandra Forssk. In Madagascar it is very common in slightly degraded pasture in Plateau areas. Trachypogon spicatus has shown tolerance of soil copper in spoils of copper mining in Zambia. High levels of copper are accumulated in the roots.

Management

Trachypogon spicatus is not cultivated.

Genetic resources

Trachypogon spicatus is widespread and common; it is not in danger of genetic erosion.

Prospects

Trachypogon spicatus is likely to remain a thatch grass and forage grass of limited value. It may gain importance in erosion control, where its limited palatability is an advantage.

Major references

  • Clayton, W.D. & Renvoize, S.A., 1982. Gramineae (part 3). In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. pp. 451–898.
  • Cope, T.A., 2002. Gramineae, tribe Andropogoneae. In: Pope, G.V. & Martins, E.S. (Editors). Flora Zambesiaca. Volume 10, part 4. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 190 pp.
  • Dougall, H.W. & Bogdan, A.V., 1958. The chemical composition of grasses of Kenya. Part I. East African Agricultural and Forestry Journal 24(1): 17–23.
  • Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO Plant Production and Protection Series No 23. Rome, Italy. 832 pp.

Other references

  • Bogdan, A.V., 1977. Tropical pasture and fodder plants (grasses and legumes). Longman, London, United Kingdom. 475 pp.
  • Drew, A. & Reilly, C., 1972. Observations on copper tolerance in the vegetation of a Zambian copper clearing. Journal of Ecology 60(2): 439–444.
  • Dujardin, M., 1978. Chromosome numbers of some tropical African grasses from western Zaire. Canadian Journal of Botany 56(17): 2138–2152.
  • ECOCROP, 2007. Trachypogon spicatus. [Internet]. FAO, Rome, Italy. http://ecocrop.fao.org/ ecocrop/srv/en/ cropView?id=148306. June 2011.
  • Everson, C.S. & Tainton, N.M., 1984. The effect of thirty years of burning on the Highland Sourveld of Natal. Journal of the Grassland Society of Southern Africa 1(3): 15–20.
  • Lütge, B.U., Hardy, M.B. & Hatch, G.P., 1998. Soil and sward characteristics of patches and non-patches in the Highland Sourveld of South Africa. Tropical Grasslands 32(1): 64–71.
  • Phillips, S., 1995. Poaceae (Gramineae). In: Hedberg, I. & Edwards, S. (Editors). Flora of Ethiopia and Eritrea. Volume 7. Poaceae (Gramineae). The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. 420 pp.
  • Silberbauer-Gottsberger, 1984. Fruit dispersal and trypanocarpy in Brazilian Cerrado grasses. Plant Systematics and Evolution 147: 1–27.
  • van Oudtshoorn, F., 1999. Guide to grasses of Southern Africa. Briza Publications, Pretoria, South Africa. 288 pp.
  • Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.

Author(s)

  • L.P.A. Oyen, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Oyen, L.P.A., 2011. Trachypogon spicatus (L.f.) Kuntze. [Internet] Record from PROTA4U. Brink, M. & Achigan-Dako, E.G. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 8 March 2020.