T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Kingdom: Plantae 
Division: Magnoliophyta 
Class: Eudicotyledoneae 
Subclass: Rosidae
(Unranked): Eurosids 
Order: Oxalidales 
Family: Oxalidaceae 
Genus: Oxalis 
Species: Oxalis pes-caprae 
Common name: Yellow sorrel, Soursob, Bermuda buttercup, African wood-sorrel, Bermuda sorrel, Buttercup oxalis, Cape sorrel, English weed, Goat's-foot, Sourgrass, Soursop

Oxalis pes-caprae is an invasive species Indigenous to South Africa, It is a however a highly invasive species and noxious weed in many other parts of the world. The plant has a reputation for being very difficult to eliminate once it has spread over an area of land. The weed propagates through its underground bulbs and this is the principal reason why it is so difficult to eradicate, as pulling up the stems leaves the bulbs behind. Soil in which the plant has grown is generally filled with small bulbs. Oxalis pes-caprae is a weed of gardens, orchards, cereal crops and pastures and invades dry coastal vegetation, heathland and heathy woodland, lowland grassland and grassy woodland, dry sclerophyll forest and woodland, riparian vegetation and rock outcrop vegetation.

Oxalis (General)
The genuses Oxalis are annual or perennial. The leaves are divided into three to ten or more obovate and top notched leaflets, arranged palmately with all the leaflets of roughly equal size. The majority of species have three leaflets; in these species, the leaves are superficially similar to those of some clovers. Some species exhibit rapid changes in leaf angle in response to temporarily high light intensity to decrease photo inhibition. The flowers have five petals, which are usually fused at the base, and ten stamens. The petal colour varies from white to pink, red or yellow; anthocyanins and xanthophylls may be present or absent but are generally not both present together in significant quantities, meaning that few wood-sorrels have bright orange flowers. The fruit is a small capsule containing several seeds. The roots are often tuberous and succulent, and several species also reproduce vegetatively by production of bulbils, which detach to produce new plants.

Oxalis spreads prolifically and is a real challenge to eradicate. The main problem is that you can pull out the weed but one leaves under the soil its parent bulb with a number of little bulblets attached to it.