Oxalis corniculata.
Creeping oxalis or Yellow Wood Sorrel is found worldwide and is naturalised in Queensland.
The perennial herbs have fibrous roots and sometimes a short taproot.
The much branched stems, to around 30 or 40 cm long are mainly prostrate.
Some stems, up to 15 cm long are erect or semi-erect.
Stems have a few to no hairs and they commonly root at the nodes.
Unlike other Oxalis species there are no bulbs.
Alternately arranged leaves are on a smooth or hairy petiole up to 5 cm long.
The small stipules, 2 mm long are fused to the petiole base along one side.
The petiole almost always has short hairs.
Leaves have 3 obcordate (inverted heart-shaped) leaflets.
They have no petiolule but there is a small pulvinus allowing the leaflets to open and close.
The around 10 to 15 mm long leaflets have a narrow notch at the tip.
The notch may extend up to half way down the leaflet.
There are short hairs on the lower surface and the edge.
The green, reddish or purple blades fold up in poor light.
Axillary inflorescences have 1 to 5 (8) flowers.
When more than one the upper flower opens first.
Inflorescences are on a peduncle up to 8 cm long with flowers on a pedicel up to 2 cm.
Both may be smooth or have hairs that are sometimes dense.
At the base of inflorescence stems are 2 narrow hairy bracts around 3 mm long.
The calyx has 5 free sepals around 4 mm long with hairs on the edge mainly at the tip.
The 5 bright yellow petals form a funnel-shaped corolla up to 1 cm long.
The fused petal bases form a corolla tube a few mms long.
The widely spreading lobes are ovate to oblong.
The 10 stamens are in 2 whorls of different lengths.
The outer ones are up to around 2 mm long and the inner around 4 mm.
The superior ovary of 5 carpels has 5 locules with numerous ovules.
The 5 free styles have a lot of short hairs.
The fruit are a roughly cylindrical green capsule around 1 to 1.5 cm long and 3 mm thick.
They are slightly 5-angled with a beak at the end formed by the styles.
There may be small simple hairs on the outer surface.
Brown to brownish red seeds, 1 to 1.5 mm wide have ridges.
Each locule may have 1 up to around 10 seeds.
Its features are variable and 8 subspecies, forms and varieties have been described but they are now all regarded as synonyms.
Plants seen in other areas may differ markedly in features such as size and the amount of hair on the parts.
The other yellow oxalis in the region is Oxalis pes-caprae which has bulbs and yellow flowers up to 4 cm across.
J.F.
