Digitaria didactyla & D. swazilandensis

Digitaria didactyla Willd.

Digitaria swazilandensis Stent

Note: These species are sufficiently similar for Digitaria swazilandensis Stent to be considered a synonym of Digitaria didactyla Willd. by a number of authorities.

None listed in GRIN for either species.

Family: Poaceae (alt. Gramineae) subfamily: Panicoideae tribe: Paniceae subtribe: Anthephorinae.

Stoloniferous perennials forming dense mats 2‒12 cm high (D. didactyla) and to 40 cm high (D. swazilandensis) . Stems prostrate with nodal roots until mat complete, then ascendant through taller vegetation; nodes brown, glabrous or pubescent. Leaf-sheaths smooth or scaberulous, densely to sparsely pilose; ligule an eciliate membrane 0.8‒2.0 mm long; leaf-blades 3–6 (–17) cm long; 2‒3 (‒5) mm wide; glaucous, surface smooth, glabrous; margins scaberulous. Inflorescence a terminal racemose digitate panicle with primary peduncle 10‒20 cm long;  racemes 2‒3 (‒4), slender, 3‒6 (‒10) cm long; occasionally branched; raceme peduncle 2‒3 mm long.   Spikelets (2–) 2.2–2.7 mm long; upper glume ½‒⅔ the length of the spikelet.  D. swazilandensis has similar habit, taller herbage, leaf blade 3‒6 mm wide, and upper glume ⅓‒½ the length of the spikelet.

Similar species

Some slender creeping specimens of D. eriantha may be difficult to distinguish from D. swazilandensis.  D. didactyla and D. swazilandensis are sometimes confused with Cynodon dactylon, but are readily distinguished because the latter is strongly rhizomatous, has a hairy ligule, and is green in colour. D. didactyla has a distinctive bluish colour and D. swazilandensis is typically intermediate in colour between D. didactyla and C. dactylon.

D. didactyla :

Asia: 蓝马唐 (China)

English: blue couch grass, blue stargrass, crabgrass, Queensland blue couch;  blue serangoon grass, green serangoon grass (Malaysia); Mauritius blue

French: petit gazon (Mauritius); gazon (Rodrigues Islands)

D. swazilandensis:

Afrikaans: skaapvingergras, swazigras, Swaziland-vingergras

Asia: หญ้าสวาซีแลนด์  (Thailand)

English: Richmond finger grass, swazi grass, Swaziland finger grass

Europe: digitaire du Swaziland (French); Swasiland-Fingerhirse (German)

Latin America: capim-suázi (Brazil); pasto swazi, suazi (Spanish)

Digitaria didactyla

Native:

Indian Ocean:  Mauritius; Réunion

Naturalized:

Asia:  Malaysia

Australasia:  Australia

Caribbean:  Puerto Rico

 Digitaria swazilandensis 

Native:

Africa:  Malawi; Mozambique; South Africa (KwaZulu-Natal, Mpumalanga, Gauteng, North West, Limpopo); Swaziland

Cultivated:

Caribbean:  Trinidad

Central America:  El Salvador; Honduras; Panama

South America:  French Guiana; Suriname; Venezuela

Forage

Although both provide excelent feed for livestock, only D. swazilandensis is sown specifically for that purpose.  However, the less productive D. didactyla often invades heavily grazed pastures, providing useful grazing for livestock while soils are moist.  Both are popular pasture grasses for horses, because they can not only withstand the often heavy grazing pressure meted out by horses, but also provide "safe" feed due to relative freedom from oxalates and nitrites found in some other grasses.

Environment

As a lawn or golf course grass, it is generally laid as turf.  D. didactyla has been used as ground cover in better rainfall areas, but is not as resilient or stable as some other ground-cover grasses such as Cynodon spp. or Paspalum notatum. On the other hand, D. swazilandensis is a more aggressive species and forms a more stable cover, to the extent that it has shown promise in suppression of the tall invasive grass weed of intensively managed pastures, Sporobolus indicus (L.) R. Br. var. major (Büse) Baaijens.

Soil requirements

Adaptated to soil textures from sands to clay loams, but not to heavy clays. Tolerant of low nutrient levels but respond well to increased fertility, particualrly nitrogen.  Prefer pH above 5‒5.5, because neither is tolerant of high Al saturation. They are also intolerant of soil salinity.

Moisture

Both species are best adapted to moist, well-drained conditions.  D. didactyla normally grows in areas with an annual rainfall in the range (700‒) 900–1,800 mm.  It survives seasonal dry conditions and drought by losing all leaf,  a characteristic that is criticised by farmers because this is when feed is in high demand.  However, it responds almost instantly to good rainfall, particularly on light soils.  It can tolerate short-term flooding, but rarely found in permanently poorly drained soils.  In Central America, D. swazilandensis is recommended in areas with an annual rainfall of 1,000‒3,000 (‒4,000) mm. With such high rainfall, good drainage is of paramount importance.

Temperature

Although both species are native or naturalized over a latitudinal range from the tropics to the subtropics, D. didactyla tends to be more widely found in the subtropics and higher altitude tropics, while D. swazilandensis has found  a commercial niche as a forage in the humid tropics.  Leaves of both species are burnt by frost and stolons killed by heavy frost.

Light

Grows best in full sunlight, extending into areas of only light shade.

Reproductive development

D. didactyla flowers and seeds prolifically from spring through to autumn. D. swazilandensis phenotypes show considerable variation in intensity of flowering and degree of seed set, some lines producing little or no seed.

Defoliation

Very resistant to mowing and heavy grazing, often invading pastures of grazing-sensitive tussock species under prolonged heavy grazing.  D. swazilandensis can produce a sufficiently deep sward to facilitate machine harvest, whereas D. didactyla is not cut for feed due to low creeping growth.  Both are excellent turf grasses under regular mowing.

Fire

Not generally burned due to moist conditions or light fuel loads under heavy grazing, but recovers quickly after fire.

Guidelines for establishment and management of sown forages.

Establishment

Seed of D. didactyla is available for lawns but is expensive so it is usually planted as turf.  Naturally spread through cattle faeces under prolonged heavy grazing.  D. swazilandensis is mostly a poor seeder and is normally established from cuttings on about a 40 cm grid.

Fertilizer

Both species are responsive to an improvement in soil nitrogen status, either through use of N fertilizer or to N from vigorous associated legumes.  Other nutrients may also be required in low fertility soils.

Compatibility (with other species)

Under heavy grazing, combines well with creeping and other native and introduced legumes, especially if superphosphate is applied.

Companion species

Legumes:  Aeschynomene falcata,  Arachis pintoi, Chamaecrista rotundifolia, Grona triflora, Glycine spp.,  Listia bainesii, Lotus uliginosus, Stylosanthes guianensis var. intermedia, Trifolium repens, Vigna parkeri.

Pests and diseases

These grasses are often prone to attack by various lepidopterous larvae, particularly when well-fertilized. Patches of grey mould on lleaves is often seen in spring and autumn.  Can be attacked by spider mites (Oligonychus spp.) and infected by Digitaria striate mosaic monogeminivirus.  D. swazilandensis is sometimes severely attacked by an Antonina species (Hemiptera, Pseudococcidae), probably A. graminis in E Venezuela, causing weakening and desiccation, but not death of the stand.  D. didactyla turf plants in Australia are also weakened by infestations of the same or similar insect.  Neither is infected by pangola stunt virus (unlike many other Digitaria spp.).  Swazi grass is less affected by moulds and other diseases than Queensland blue couch.

Ability to spread

Spread rapidly by runners and seed, particularly under persistent heavy grazing or regilar mowing.  Seed reserves can be high in the soil;  germinable seed can be spread through dung of cattle on well grazed pastures (up to 20 germinable seeds/g faecal DM).

Weed potential

D. didactyla seeds fairly freely and spreads more by seed than D. swazilandensis. However, both are primarily stoloniferous and easy to kill with common contact and translocated grass herbicides, unlike the strongly rhizomatous Cynodon dactylon.

Nutritive value

See Feedipedia.

Palatability/acceptability

Very palatable.

Toxicity

None reported.

Feedipedia link

https://www.feedipedia.org/node/454 (D. swazilandensis)

Dry matter

Up to 11 t/ha DM recorded from D. didactyla with fertilizer application of 225 kg/ha N, but very low yields without N.  Yields of 9‒20 t/ha DM have been obtained in Central America from D. swazilandensis.

Animal production

Liveweight gains of no more than about 90 kg/head/year are achievable on heavily grazed, unfertilized stands of D. didactyla.  Liveweight gains averaging 0.5 kg/hd over long periods at quite high stocking rates have been achieved from cattle grazing D. swazilandensis pasture without supplement.

Commercial varieties have largely been derived from selections from wild populations or seedlings therefrom. In the absence of definitive data, observations of the variation in the progeny of selected plants suggest at least a proportion of outcrossing in both species.

D. didactyla 2n = 18, 36.

D. swazilandensis 2n = 18, 54

Seed harvest is difficult due to low growth.  In south-east Queensland (Australia), yields of 100 kg/ha seed have been recorded in 2 harvests; in January and November.  Seed remained viable (with germination up to 80%) over 2 years when stored at 15 °C.  Dehulling seed reduced germination, probably because of damage to the caryopses.

Seed growers in Queensland, Australia, typically fertilise seed crops by the end of October (spring), though this can be up to a month earlier depending on seasonal conditions.  The amount of Fertilizer N used on established paddocks varies from 55‒85 kg N/ha on the fertile soil to c. 140 kg N/ha on the infertile soil.  Depending on the starting date, seed crops may be harvested in late December, though January is more usual.  Seed growers in Queensland typically mow the ripe seed crop, and then pick it up from the windrow with a combine harvester 1‒3 days later unless drying has been delayed by wet weather.  Excessive rainfall during the summer growing period can lead to crop failures.  A second seed crop in late autumn is sometimes possible.

Tolerant of a range of broadleaf herbicides, including 2,4-D, MCPA, dicamba, fluroxypyr, metsulfuron, trifloxysulfuron.  Susceptible to the organoarsenate herbicides, MSMA (monosodium methanearsonate) and DSMA (disodium methanearsonate).  D. swazilandensis has some tolerance to fluazifop, which could be used for the selective control of other grasses.

• Very palatable.
• Good quality.
• Very resistant to heavy grazing.
• Good ground cover.

• Low production during dry periods.
• Intolerant of waterlogging.
• Intolerant of shade.
• Weed ingress in heavily grazed pastures.

Loch, D.S., McMaugh, P. and Scattini, W.J. (2013) A review of Digitaria didactyla Willd., a low-input warm-season turfgrass in Australia: Biology, adaptation and management. International Turfgrass Society Journal 12:1–14. espace.library.uq.edu.au/view/UQ:325603

Strickland, R.W. (1973). A comparison of dry matter yield and mineral content of three forms of Cynodon with Digitaria decumbens and D. didactyla. Tropical Grasslands 7:313–317. bit.ly/2R76E9h

‘Aussieblue’ Released in Australia (1997).  Origin unknown.  Derived from a line ostensibly introduced to Australia from Trinidad as Digitaria longiflora SR 1232-1 and catalogued as CPI 40639 (more likely SR 1233-1 D. swazilandensis).  Both lines came to Trinidad from USDA.  Useful for lawn turf having vigorous lateral spread, wide leaf and sparse flowering.  Compared with Queensland blue couch, it is more robust in appearance with broader, lighter coloured, less bluish-green leaves, and fewer but larger inflorescences.  It spreads more rapidly by stolons, and forms a denser, more easily maintained sward.

'Tropika Blue' Derived from a seedling of unknown origin growing at the Department of Primary Industries, Mareeba (QLD); this differed from known material of the 4 accessions then being distributed experimentally. Compared with 'Aussiblue', 'Tropika' has slightly broader leaves that are darker blue-green in colour.

CPI 40674, CPI 40676 Selected at Grafton, New South Wales, Australia.  Origin unknown.  Introduced to Australia from Trinidad, previously from USDA, and prior to that from South Africa.  Both lines produce viable seed, CPI 40674 more than CPI 40676.  Both lines produce higher yields than naturalized D. didactyla in the Australian subtropics, and have larger leaves.