YES I AM SERIOUS ! Soursob & Veldt Grasses are smothering our native wildflowers. Have you noticed the change along roadsides and creeklines?
Soursob, oxalis pes-caprae, is an aggressive weeds species common to the Strathbogie Ranges. This persistent perennial herb enjoys riparian settings. Unfortunately the banks of the lower reaches of the Seven Creeks are covered in masses of this plant, mainly because the bulbs can be dispersed by water during floods.
Soursob has a severe impact on indigenous ground flora with dense infestations smothering and eradicating smaller plants. It originates from Southern Africa.
It proves hard to eradicate unless controls are well timed and persistent over several years. The Euroa Arboretum Bush Crew have been treating large patches along the creek in town with some success.
The foliage emerges by mid winter and new bulbils form underground over late winter to spring. Soil disturbance leads to major population expansions and in large infestations there are as many as 3000 plants per square metre.
Winter is the time to control plants. This should be done in the bulb exhaustion phase just prior to flowering or the early flowering stage . Spray with a broadleaf selective herbicide that will not kill native grasses. ( triclopyr, fluroxypyr , dicamba, or MCPA ) Repeated applications over 2 to 5 years are commonly required. Occasional plants can be carefully dug out. Never hand pull as the bulbs will inevitably dislodge and be left in the soil to reproduce.
A similar looking native species is Wood Sorrel but no indigenous oxalis species have bulbs.
Reference : Bush Invaders of SE Australia by Adam Muyt..