The milkwort is a low-growing, hairless perennial plant.

It has small entire leaves and irregular flowers collect in racemes.

The corolla's colour can be blue, lilac, pink or white, but the blue is more common. These four colours account for its Irish folk-name of "four sisters".

It can be found in pastures, banks, bog-margin, sand-hills and rocky ground and it is very common. The botanical name is Polygala vulgaris and it comes from the ancient Greek meaning "much milk", in fact the plant can increase milk yields in cattle.

The Irish name is Na deirfiùrìnì.