Yellow Wood-sorrel, Creeping Oxalis
Introduced forb to 30cm tall, sometimes creeping. Leaves alternating up the stems, each composed of 3 leaflets, each 0.4-2cm long, 2.4-25mm wide, flat, hairless to hairy, with a notched or squared off apex. Flowers yellow, with 5 petals, in umbels of 1-6 flowers on stems arising from the bases of the leaves .
Note that the description and photo in G.M. Cunningham, WE Mulham, PL Milthorpe and J H Leigh (1981 and later printings) Plants of Western New South Wales page 435 was written before the native species were segregated from Oxalis corniculata.