A carnivorous plant, as are all the members of the Bladderwort family, Lentibulariaceae, Common Butterwort has evolved to trap insects in its leaves to make up for any mineral deficiencies in the soil, as it grows on bare wet rocks, stony heath, peat bog and moorland all around Scotland.
It is a perennial plant, growing from a basal rosette of leaves, to produce 1 or a few straight reddish stems which support a single flower. The leaves are the trap for unsuspecting insects. They are oval, yellowish green and smooth-edged, growing sessile from the central stem, or sometimes on very short stalks.
The edges of the leaves curl inwards, slowly rolling up to digest the fly as enzymes are secreted from the leaf. The insect has already been rendered immobile by a sticky substance oozing from glands on the leaf’s surface, and can only watch helpless as it is engulfed in leaf.
The violet flowers have 5 unequal petals, fused at the base into a tube with a backward spur, similar to that of a Violet. The lower 3 flower lobes are longer than the upper 2. Inside the tube are 2 short stamens and a short thin style.
The fruit is a 2-pronged brown nut, which splits lengthwise into 2.