Flowers of Oxalis tetraphylla (Four-leaved Pink-sorrel). It is commonly grown as an ornamental plant for its foliage, remsembling a four leafed clover with a dark colouration around the base of each leaf. It is sometimes known as "Lucky leaf" or "Four-leaf Clover" for this reason, though it is not related to clovers.
The flowers are a strong pink colour with a green centre. The petals are strongly veined, with the veins leading back to the centre of the flower.