Bulbous Poa

Poa bulbosa L.

Synonyms -

Family: Poaceae

Names:

Poa is from the Greek word meaning grass.
Bulbosa refers to the swollen bases.

Other Names

Bulbous Bluegrass
Bulbous Meadowgrass
Bulbous Poa.
Bulbous-rooted Poa

Summary:

A tufted, erect, bulbous based perennial to 40 cm high with very narrow leaves and a somewhat compact, erect, green seed head. The leaves have a hooded tip.

Description:

Cotyledons:

One.

First Leaves:

Long and narrow.

Leaves:

Emerging leaf folded flat in the bud.
Blade - Green to grey green, long, narrow, 10-100 mm long x 1-2 mm wide, flat, folded or in rolled. Tip hooded, abruptly pointed. Hairless but sometimes rough on the keel and veins underneath.
Ligule - Membranous, to 4 mm long, triangular, pointed tip.
Auricles - None or may be a small swelling.
Sheath - Enlarged and fleshy inner sheaths. Hairless.

Stem leaves - none.

Stems:

Tufted, erect or spreading, 50-400 mm tall, unbranched, 2-4 noded. Pear shaped swollen base. Hairless

Flower head:

Dense, erect panicle, of clustered spikelets, many fine branches, egg shaped to oblong, 20-60 mm long x 10-25 mm wide. Branches usually rather erect and roughened but hairless. Breaks above the glumes and between the florets.
In some forms a bulbil or miniature shoot forms in the spikelet replacing the normal floret and these may fall to form new plants.

Flowers:

Spikelets - Variegated with green, white, gold and purple, 3-6 flowered, 3-6 mm long, flattened, egg shaped to broadly oblong. On short stalks, 0.3-3 mm long.
Florets - 2.5-3.5 mm long
Glumes - 2-3 mm long, 3 nerved, boat shaped, keeled, membranous, persistent, shorter than the florets. Rough on the keels and edge vein.
Lemma - 2.5-3.5 mm long, finely 5 nerved, broadly lance shaped. Long hairs on the keel and side veins. Midrib hairless on the lower lemma but increasingly hairy on upper lemmas. Fine crinkled hairs at the base. Awnless.
Stamens -
Anthers -

Seeds:

Brown. Oval to tear shaped, 1 mm long x 0.5 mm wide. Hairy base. Tip pointed.

Roots:

Fibrous.

Key Characters:

Perennial.
Leaves glabrous
Plants bulbous at the base with elongate conical or pear shaped bulbs composed of the enlarged and fleshy inner basal leaf sheaths.
Membranous ligule.
Spikelet 3-6 flowered in contracted panicle.
Lemma entire, keeled, thin, woolly near base.
Adapted from John Black, Nancy Burbidge

Biology:

Life cycle:

Perennial. Seeds germinate in autumn. Makes good growth over winter. Tops die off over summer and quickly disintegrate leaving the bulbous bases that blow around and form new plants in the next autumn.

Physiology:

Tolerant of slightly saline soils.
Fairly drought tolerant.

Reproduction:

By seed, bulbous bases and occasionally bulbils in the seed head.

Flowering times:

September to October in SA.
Spring in western NSW
Spring and summer in WA.

Seed Biology and Germination:

Vegetative Propagules:

Bulbous leaf bases and bulbils.

Hybrids:

Several forms.

Population Dynamics and Dispersal:

Spread by seed and wind blown bulbous leaf bases.

Origin and History:

Mediterranean, Europe, Asia, North Africa, South west and central Asia

Distribution:

ACT, NSW, QLD, NT, SA, TAS, VIC, WA (Pemberton).

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate

Soil:

Sandy skeletal soils in drainage lines

Plant Associations:

Significance:

Beneficial:

Used as a golf course grass.
Fodder

Detrimental:

Weed of crops, pastures, grass land, disturbed areas.

Toxicity:

Not recorded as toxic.

Symptoms:

Treatment:

Legislation:

None.

Management and Control:

Grazing usually provides adequate control. Most grass selective herbicides are ineffective. Tralkoxydim (e.g. Achieve®) may provide some control.
Burning is likely to lead to an increase in the infestation.

Thresholds:

Eradication strategies:

Cultivate during winter. Spray with knockdown herbicides during winter.

Herbicide resistance:

None reported.

Biological Control:

Related plants:

Annual Poa (Poa annua)
Blue Tussock Grass (Poa poiformis, Poa australis) has a short membranous ligule and may have slightly swollen bases.
Kentucky Bluegrass (Poa pratensis)
Knotted Poa (Poa drummondiana) also has bulbils or 1-3 swellings at the base of each stem but a much looser head
Rough Meadow Grass (Poa trivialis) is similar but perennial, stoloniferous, has a longer ligule at 4-10 mm long and a web of hairs at the base of the lemma.
Scaly Poa (Poa fax, Poa lepida)
Snowgrass (Poa sieberiana)
Sweet Swampgrass (Poa fordeana)
Tussock grass (Poa labillardieri)
Poa compressa
Poa trivialis ssp. sylvicola

Plants of similar appearance:

Grasses.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P153.

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

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P29.

Ciba Geigy (1981) Grass Weeds 2. CIBA GEIGY Ltd, Basle, Switzerland. P119. Diagrams.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P133.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

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). P66.

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

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). 800.2.

Moerkerk, M.R. and Barnett A.G. (1998) More Crop Weeds. (R.G and F.J. Richardson, Melbourne). P39. Photos. Diagrams.

Paterson, J.G. (1977). Grasses in South Western Australia. (Western Australian Department of Agriculture Bulletin 4007). P80. Diagram.

Acknowledgments:

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