Bermuda buttercup
Oxalis pes-caprae
Family · Oxalidaceae · Irritating
The yellow carpet over southern fields from December to April. Everyone called it clover as a child and sucked its sour stem, and almost nobody knows it is an invader from South Africa.
Fields and pasture · Roadsides and waste ground · Town and roadside · Walls and rocks
Also known assourgrass, African wood-sorrel
How to tell it
Three heart-shaped leaflets, often with dark flecks, and yellow cup flowers on a leafless stalk. It closes its flowers late in the day and on cloudy days.
What it is confused with
Clovers
Trifolium spp.
Clover has oval leaflets with a pale V mark and flowers in a round head. Sourgrass has heart-shaped leaflets, notched in the middle, and a five-petalled yellow flower.
What it is for
The stem is sour and has always been chewed by children, but that sourness is oxalic acid, and in quantity it is not harmless, especially for anyone with kidney problems. A plant for a taste, not a handful.
Traditionally used as food. This is not permission to eat it.
The law says
Listed as an invasive alien species in Portugal. Do not propagate, transport or plant it, not even in a pot.