Annual Pearlwort

Sagina apetala Ard.

Synonyms - Colobanthus apetalus and Colobanthus billardieri misapplied.

Family: Caryophyllaceae.

Names:

Sagina is Latin for fattening nourishment.
Apetala is Latin meaning without petals
Annual Pearlwort.

Other names:

Common Pearlwort
Pearlwort.

Summary:

An open, tufted, erect annual herb to 15 cm tall with small opposite leaves and terminal, loose, sprays of flowers without obvious petals in spring.

Description:

Cotyledons:

Two.

Leaves:

No rosette. Paired, the pairs joined across the stem by a papery membrane.
Stipules - None
Petiole - None.
Blade - Parallel sided to tapering to a fine point, 2-15 mm long x 0.5 mm wide. Tip tapered into an awn formed by the protruding midrib. Edges sometimes hairy toward the base.

Stems:

Erect or bending upwards, much branched, 25-100(150) mm tall, thread like, tufted. Sometimes grows in clumps with unbranched stems, 10-20 mm long.

Flower head:

Cymes of 1 or 2 flowers at the ends of branches, or in upper leaf axils. Flower(s) on long, slender, thread like, erect hairless or sparsely hairy, erect stalks (peduncles), 3-15 mm long.

Flowers:

Ovary -
Sepals - Usually 4. Egg shaped to oblong. Hooded at the top. 1.5-2 mm long. Hairless or sparsely glandular hairy. Usually blunt or outer sepals longer and pointed and inner ones blunt. Hooded at the tip.
Petals - Usually absent or very small.
Stamens -4 opposite the sepals.
Anthers -

Fruit:

Egg shaped capsule, 1.5-2.5 mm long. Opening by 4 valves.

Seeds:

Many, brown, egg shaped, small. Hairy.

Roots:

Slender, fibrous.

Key Characters:

Leaves without stipules, the pairs joined across the stem by a scarious membrane, mucronate, does not from a rosette of leaves.
Styles, 4, free or almost so.
Sepals, 4, free or almost so, usually with one central nerve, rarely 3 nerved, 1.5-2 mm long, oblong-lanceolate.
Petals, 4, entire or absent.
Fruit a capsule opening to the base by 4 valves.
Seeds several or numerous.
Erect annual.
Adapted from J.M. Black, N.T. Burbidge and J.R. Wheeler.

Biology:

Life cycle:

Annual. Flowers August to November.

Physiology:

Reproduction:

By seed.

Flowering times:

August to November in SA.
September to November in Perth.

Seed Biology and Germination:

Vegetative Propagules:

None.

Hybrids:

Subspecies Sagina apetala ssp. erecta appears to be the most common in Australia.

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Europe, North Africa, Western Asia, America.

Distribution:

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

Courtesy Australia's Virtual Herbarium.

Habitats:

Moist areas.

Climate:

Temperate. Mediterranean.

Soil:

Plant Associations:

Significance:

Beneficial:

Detrimental:

Weed of cultivated areas, lawns, stone and brick work, garden paths, gardens, granite outcrops, salt lake edges, woodlands and disturbed areas

Toxicity:

Not recorded as toxic.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Prevent seed set.

Herbicide resistance:

Biological Control:

Related plants:

Sea Pearlwort Sagina maritima has small white petals.
Spreading Pearlwort (Sagina procumbens) is a compact, prostrate perennial with rosettes of leaves and single flowers.

Plants of similar appearance:

Four-leaved Allseed (Polycarpon tetraphyllum) has broader leaves.
Corn Spurrey (Spergula arvensis) has narrower leaves with petalled flowers.
Australian Crassula, Dense Crassula, Spreading Crassula (Crassula spp.)
Chickweed (Stellaria media)
Mouse-eared Chickweeds (Cerastium spp.)
Pimpernel (Anagallis arvensis)
Waterblinks (Montia spp.)
Pigweed (Portulaca spp.)
Petty Spurge (Euphorbia peplus) exudes a white sap when damaged.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P144-145. Diagram.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P354.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P162. 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). P130-131. Photo.

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). #1078.1.

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). P107.

Acknowledgments:

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