Reed Sweet grass

Glyceria maxima (Hartman) Holmb.

Synonyms - Glyceria aquatica, Poa aquatica.

Family: Poaceae.

Names:

Glyceria is from the Greek glyceros meaning sweet referring to the taste of the seeds on some species in this genus.
Maxima is from the Latin magnus meaning large because this species is the largest in the genus.
Reed Sweet grass refers to its association with reeds and wet areas and it membership of the Sweet grass genus.

Other names:

Glyceria
Reed
Reed-grass
Reed Meadow grass
Water Meadow grass

Summary:

Reed Sweet Grass is a luxuriant, leafy, robust, perennial aquatic grass from 900 to 2500 mm tall. It arises from stout widely spreading rhizomes that produce both vegetative and flowering shoots, the vegetative being more numerous. The seed head is a narrow to open, green panicle that is 12-45 cm long.

Description:

Cotyledons:

One

Leaves:

Blade - 300-600 mm long x 7-20 mm wide, bright green with an abruptly pointed tip. On the outside of the leaf, where the blade joins the sheath, there is a pale triangular patch on either side of the midrib. Rough on the edges and sometimes on the lower surface also. Hairless. Upper leaves have indistinct cross veins.
Ligule - Membranous, white, rounded, and usually with a central point. 3-6 mm long
Auricles - None.
Sheath - Slightly rough to touch. Cross veined.

Stems:

Erect or bending upwards at the ends, stout to robust, smooth or rough in the upper parts, 900-2500 mm tall. Stout rhizomes that produce both vegetative and flowering shoots.

Flower head:

Oblong and many branched panicle 120-450 mm long. Large and wide spreading or dense and compact, many slender, rough branches with the lower ones to 200 mm long. It produces large numbers of spikelets. As seed matures the branches may become pressed to the main axis giving the flowering head a more narrow appearance.

Flowers:

Spikelets - Usually 3-5 mm long or less than 10 mm long, yellow or green or purplish, slightly flattened, narrowly oblong, 5-12 mm long x 2-3.5 mm wide with 4-10 florets. Obtuse tip. Stalked.
Florets - 3-4 mm long, blunt and not toothed at the tip.
Glumes - Elliptic, membranous. Obtuse tip. Lower glume 2-3 mm long. Upper glume 3-4 mm long.
Palea - 2.5-3 mm long. Obtuse tip.
Lemma - 2.5-3 mm long, rough to touch, 7 ribbed. Obtuse tip.
Stamens -
Anthers -

Fruit:

Seed enclosed in persistent, hardened flowering glumes.

Seeds:

Dark brown, 1.5-2 mm long.

Roots:

Stout rhizomes and fibrous roots.
Fibrous roots are 1-2 mm diameter, several rising from each rhizome node, extending to depths of 1 m and giving rise to laterals 10-80 mm long.

Key Characters:

Membranous ligule.
No auricles.
Pale triangular patch at the collar.
Stout rhizome.
Wet and shallow water areas.

Biology:

Life cycle:

Perennial. Seeds germinate in spring and seedlings grow rapidly producing a mat of creeping rhizomes in summer and autumn. Growth slows in winter. In its first year the seedling usually produces vegetative shoots only, flowering occurring for the first time in the second year. Once established, the rhizomes grow rapidly in to clean areas in the warmer months and produce many vigorous vegetative shoots and some flowering shoots. Growth slows and many shoots fail to mature as the suitable area is filled.

Physiology:

Sensitive to anaerobic conditions. Under these conditions sugar levels and digestibility drop rapidly reducing its nutritive value.

Reproduction:

By seed and rhizomes.

Flowering times:

Summer in western NSW.
Summer in WA.

Seed Biology and Germination:

Dormant seeds remain viable for several years.
Fresh seed has a high germination percentage.

Vegetative Propagules:

Rhizomes and rhizome fragments.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Once the plant is established most local spread is by creeping rhizomes and rhizome fragments. Seedlings don't establish in dense vegetation. New infestations arise from rhizome fragments or seed distributed by running water or in mud transported on animals, birds or machinery.
Rhizomes may grow 30 metres and produce 100 shoots in the first 2 seasons. The rhizome mass may account for 40 to 55% of the total weight of the plant.
Spread is limited by depth of water, anaerobic conditions and dry land. Very little ventures into water over 1500 mm deep or onto land that isn't periodically flooded and quite wet for most of the year.

Origin and History:

Europe. Temperate Asia. North America.
Introduced as a pasture grass.

Distribution:

NSW, QLD, SA, TAS, VIC, WA.
Scattered throughout the agricultural areas of Tasmania, particularly in the vegetable growing areas of the north-east and north-west.
NSW Tablelands, south western slopes of the Great Dividing Ranges, irrigation districts in the south.
Victoria in Gippsland, northern region, western district.
SA Mount Lofty Ranges, south-eastern districts.
WA lower south west coastal district.

Courtesy Australia's Virtual Herbarium.

Habitats:

Wet or periodically flooded sites. Along banks of slow moving rivers, creeks, canals, drainage ditches, lakes, ponds, farm dams. It grows in water up to 1500 mm deep and often forms floating 'rafts' over much deeper water.

Climate:

Temperate areas.

Soil:

Aquatic areas.

Plant Associations:

Aquatic plants.

Significance:

Beneficial:

Swamp forage of reasonable quality if grazed to keep it short. Related species are considered to be a nutritious fodder in Europe.

Detrimental:

One of the most serious aquatic weeds in Tasmania. Dense stands of this grass will impede water flow, cause local flooding, reduce holding capacity of farm dams and accelerate siltation.
Weed of the banks of slow moving rivers, creeks, canals, drainage ditches, irrigation channels, lakes, ponds and farm dams.
Becoming a serious weed of wetlands in WA.

Toxicity:

It is one of the main causes of cyanide poisoning of livestock in Tasmania and NZ.

Legislation:

Noxious weed of Tasmania.

Management and Control:

Thresholds:

New infestations should be treated promptly before rapid spread occurs.

Eradication strategies:

Glyphosate in late summer and autumn, at flowering, gives good control. Use surfactant and mix with 2500 to 3500 litres water per hectare to ensure complete wetting of foliage. Tolerates many grass-killing herbicides.
Mechanical control is ineffective.

Herbicide resistance:

Biological Control:

Related plants:

Glaucous Sweet grass (G. declinata).
Manna grass (G. australis)

Plants of similar appearance:

Rushes and reeds.

References:

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P109.

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). P56. Photo.

Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P110-111. Diagrams.

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

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #590.4.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P962.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P109-111. Photos. Diagram.

Acknowledgments:

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