Rhodes Grass

Chloris gayana Kunth

Synonyms - Chloris abyssinica

Family: Poaceae.

Names:

Chloris is from the Greek word chloros meaning bright green and refers to the leaf colour.
Rhodes Grass - Named after the empire builder Cecil Rhodes who introduced it to agriculture.

Other Names

Hunyanigrass (Europe)
Grama Rhodes, Pasto Rhodes (Spain).

Summary:

An erect almost hairless, stoloniferous or tufted, summer growing perennial grass 0.5 to 1.2 m tall.

Description:

Cotyledons:

One.

First leaves:

Single.

Leaves:

Young leaves rolled in the bud.
Blade - Green, flat, (1.5)3-9(15) mm wide by (60)150-500 mm long. Length to width ratio is 20-40. Folded near the base and tapering gradually to a fine tip. Slightly rough to touch on the upper surface or along the keel. Hairless or occasionally some sparse long (2-3 mm) hairs on the upper surface especially near the collar.
Ligule - Hairy membranous ring with hairs to 6 mm long. Membranous section is very short.
Auricles - None.
Sheath - Compressed, keeled, smooth to rough to touch (scabrous), hairless or with hairs or bearded near the junction with the blade. Sheaths are loose especially the uppermost.

Stems:

The stolon stems are 4-5 mm diameter by 50-1000 mm long.
The fertile stems (culms) are 2-4 mm diameter x 800-1500(2000) mm tall, simple or branched, wiry and tough, erect or bent at the nodes and often with a prostrate section that may root at the nodes with the rest of the stem ascending. Often forms barren shoots or leafy, wiry and tough flattened stolons or runners that root and shoot at the nodes. This depends on the genotype or cultivar. The stems and shoots are smooth and hairless.
Cultivar Callide has strong runners (stolons) and forms a dense covering.

Flower head:

Simple or branched with (3)6-18(30), somewhat erect, finger-like, sessile spikes (sometimes in 2 whorls) at the tops of the stems. The spikes are 40-150 mm long and brownish green becoming darker brown to straw coloured with age. Spikelets crowded on the spike and arranged in alternate rows on one side of the slender axis (rachis). The main axis and branch axis are hairless but rough to touch (scabrid).

Flowers:

Spikelets - crowded, 3-5 mm long, sessile, all similar, 2-4 flowered. They break above the glumes. Callus short and obtuse and minutely bearded.
Florets - The lowest one (rarely 2) is usually bisexual, the second is male and one or two sterile,
Glumes - Membranous or translucent, 1 nerved, persistent, awnless. First glume is about 1/3 the length of the spikelet, 1-2.8 mm long, egg to lance shaped, awnless.

Second glume is about 2/3 the length of the spikelet, 2-4 mm long, oblong, rather obtuse tipped with a small point (mucronate, cuspidate) and slightly rough to touch, 3 ribbed.
Palea - Same size as the lemma, 2-3 mm long with rough to touch (scabrid) keels.
Lemma - Cartilaginous, 3 nerved. The first lemma is 2.5-4.2 mm long, oval to oblong, sub obtuse to acute, 3 nerved, obscurely 2-lobed, hairy (pubescent) on the submarginal veins near the base and with long stiff white hairs (ciliate) to 1 mm long near the top, keels and edges. First lemma awn is straight and 0.8-5(10) mm long, as long or longer than the lemma, rough to touch (scabrid) and more or less terminal arising from the notch. The second lemma is 2 mm long, flat topped (truncate), obtusely tipped or notched, smooth with a 1-5.5 mm awn arising from the tip. Upper lemmas awnless and flat topped (truncate) or obtusely tipped and a relatively long stalk. Third and fourth lemmas if present are awnless and empty.
Stamens -
Anthers - Usually 3 but the third or higher florets may have none.

Seeds:

Brown, oval, 2 mm long x 0.6 mm wide.
Spikelets break off above the glumes and seed separates readily from the spikelet in most cultivars.
Cultivar Katambora has larger spikelets with about 4 million spikelets/kg compared to 7-10 million spikelets/kg for most other varieties.
The seed weight is about 0.5 mg or 2 million seeds/kg.

Roots:

Fibrous. Well developed deep root system. Roots to 4.7 m deep but few roots extend beyond 2.4 m.

Key Characters:

Stoloniferous perennial.
Inflorescence a subdigitate umbel.
Spikes frequently in 2 whorls.
Callus minute, obtuse.
Spikelets singly arranged in 2 rows along the rachis, blunt at the apex,
Florets imperfect, 3-4, at least one bisexual.
Imperfect florets obtuse or truncate and usually inflated.
Lemma laterally compressed.
Lemma of lowest floret ciliate or sparsely hairy on the lower part of the margins with hairs to 1 mm long and awned.
Adapted from J. Black, S.W.L Jacobs, S.M. Hastings, and T.D. Macfarlane.
Awn length can be useful to distinguish between cultivars.

Biology:

Life cycle:

Perennial or occasionally annual. Seed germinates 1-7 days after planting or in Spring and it grows rapidly over summer. Seed heads are formed in summer. Stolons may form in the first and subsequent summers to spread the plant. It makes little growth over the cooler winter period. In some environments with long dry periods or cold winters it may act as an annual.

Physiology:

Drought tolerant and salt tolerant. Tolerates >10 mS/cm total salts.
Tolerates fire and grazing when well established.
Sensitive to frost. The original Pioneer cultivar appears to be the most frost tolerant.
Tolerates high lithium but not magnesium and is intolerant of high soil manganese.
Low night temperatures reduce the seed set of cultivars Callide and Pioneer.
It doesn't tolerate shady conditions.
Feed quality drops quickly after flowering and most stands are rotationally grazed on a 28 day cycle to keep the stand vegetative but not overgrazed.
Tolerates poor soils but has very poor production and persistence. It is very responsive to phosphorous and nitrogen in most soils.

Reproduction:

By seed and stolons.
Generally cross pollinates with only 1-4% self compatibility. Cultivar Callide appears to be self pollinating.

Flowering times:

Summer to autumn in western NSW.
March to July is SA.
January to May in WA.
Cultivar Callide flowers mainly around April.
The diploid forms (2n=20) are generally light insensitive and flower throughout the growing season. The tetraploids respond to shortening day length and there is a flush of flowering as the day length falls below 12 hours with limited flowering at other times of the year. This usually results in a heavy flowering in mid April and a lesser flush in October to November.

Seed Biology and Germination:

Seed from diploid forms have little or no dormancy. Seed from tetraploid forms may not reach maximum germination for 3-6 months after harvest and occasionally up to 18 months after harvest.

Vegetative Propagules:

Stolons.

Hybrids and Cultivars:

Callide flowers later and is more productive than Pioneer.
Katambora flowers later and is more productive than Pioneer and is reniform nematode resistant.
Nemkat is reniform nematode resistant.
Pioneer was named in 1966 and is the original introduction from South Africa.
Sawford
Topcut

Population Dynamics and Dispersal:

Spread by seed and runners. Seed is spread in water flows, by wind and by adhering to animal fur.
Usually planted at 0.5 to 1 kg seed/ha or vegetative stolons planted on a 1 m grid.

Origin and History:

Native to tropical and subtropical Africa 284. It is widely naturalised in Africa and it exact origin is obscure.
Introduced as a fodder plant, soil stabiliser and salt land reclamation species.
Commercial cultivars were introduced around 1900 from South Africa.

Distribution:

ACT, NSW, QLD, NT, SA, VIC, WA.

Courtesy Australia's Virtual Herbarium.
Lord Howe Island. New Zealand. North America. South America. North Africa. India. Middle East. South East Asia. China. Tropical Africa to Asia.

Habitats:

Prefers open sunny situations, open woodlands, grasslands, river and lake margins, seasonally waterlogged areas

Climate:

Tropical to temperate.
Usually requires 600-1000 mm annual rainfall with a significant proportion in the summer. It doesn't thrive in areas with more than 1800 mm rainfall/year.
Tolerates short term waterlogging and up to 15 days flooding.
Tolerates average annual temperatures of 16.5 to >26 degrees C.
Reported optimum temperatures for growth vary widely but are probably in the 20-370C range.

Soil:

Prefers red earths and loams but grows on a wide range of soils from clays through to sands.

Plant Associations:

Significance:

Beneficial:

Soil binder, fodder, shelter, drought tolerant, salt tolerant.
Capable of producing large quantities of feed in areas with higher summer rainfall. Can often be grazed within 4-6 months of planting with maximum production in the second year.
Occasionally used in irrigated pastures.
Cultivars Katambora and Nemkat are resistant to the reniform nematode (Rotylenchulus reniformis) and are used to reduce nematode numbers.
Makes good hay if cut before flowering. Generally doesn't make good silage.

Detrimental:

Weed of roadsides and areas adjacent to plantings.
Minor environmental weed and unlikely to seriously invade natural bushland because it doesn't tolerate shade. It may invade disturbed areas but usually dies out in 4-5 years if no further disturbance occurs or if it is controlled to allow taller growing species to establish.
Suppresses woody regrowth.

Toxicity:

Not recorded as toxic.
Contains low levels of oxalic acid.
Some suspicion of rarely causing skin complaints.

Symptoms:

Treatment:

Legislation:

None.

Management and Control:

Fire and grazing are not very effective on established stands.

Thresholds:

Eradication strategies:

Tolerates normal rates of glyphosate.
Use 100 mL of glyphosate(450g/L) in 10 L water in early summer when the plants are actively growing or 6 L/ha on larger areas. 2 L/ha of metolachlor (720g/L) can be used as a pre-emergence treatment in spring to stop seedling establishment.
Haloxyfop can be used in bushland or where damage to broad leaved species needs to be minimised.
Repeat sprays may be required when regrowth is actively growing.

Herbicide resistance:

Biological Control:

Diseases rarely cause economic impact on Rhodes Grass.
A number of insect pests including Armyworm can cause significant damage in some years.
Striga lutea and Striga asiatica may parasitise it.

Related plants:

Purpletop Chloris (Chloris barbata) is introduced and in Northern Australia.
Slender Chloris (Chloris divaricata) is in Queensland and New South Wales.
Rhodes Grass (Chloris gayana) is introduced and has an awn on the first lemma about the same length as the lemma.
(Chloris lobata)
Comb Chloris (Chloris pectinata)
Chloris pumilio = Chloris ruderalis
Windmill Grass (Chloris truncata) is introduced and has an awn on the first lemma much longer than the lemma.
Feathertop Rhodes grass (Chloris virgata) is introduced.
Tall Chloris (Chloris ventricosa) is in Queensland, New South Wales and Victoria.
(Oxychloris scariosa = Chloris scariosa)
(Enteropogon acicularis = Chloris acicularis)
Chloris inflata is in New Guinea.

Plants of similar appearance:

Perennial grasses
Carpet Grass (Axonopus compressus)
Couch (Cynodon dactylon)
Paspalum (Paspalum dilatatum)
Sourgrass (Paspalum conjugatum)
Saltwater Couch (Paspalum distichum)

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P203. Diagram.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Ciba Geigy (1981) Grass Weeds 2. CIBA GEIGY Ltd, Basle, Switzerland. P48. Diagrams.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P74. Photo.

Gardner, C.A. (1951) The Flora of Western Australia. Vol 1. Part 1. Gramineae. P220.

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 4. P518. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P43. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne). P65. Photos.

Lamp, C. A., Forbes, S. J. and Cade, J. W. (2001). Grasses of Temperate Australia. Revised Edition. (Blooming Books, Melbourne). P118. Diagram.

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #238.2.

Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P947-948.

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P99.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P38-39. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.