I like to think as insectivorous plants as a perverse, natural revenge by plants on the animal kingdom. The prey has become the predator as they have evolved the ability to lure, trap and digest insects. This facility to acquire additional nutrients enables them to grow in habitats with poor soils such as wetland heaths and bogs. Our native insectivorous plants may not be as flamboyant as some of their more exotic relatives from the tropics, but they have a subtle charm and delicacy which masks their fatal attraction.
In the Outer Hebrides there are nine species from the three groups of insectivorous plants found in the UK – the Bladderworts, Butterworts and Sundews.
Sundews
The Round-leaved Sundew (Drosera rotundifolia) is probably the most well know of our native insectivorous plants. Small, and delicate, they are usually found in wet, acidic habitats, often nestling among sphagnum moss. Their perfectly, round leaves are fringed with red tendrils which glisten with droplets. The leaves are held aloft to lure small insects with an offering of “dew”. The droplets are sticky, and the more the insect struggles, the more mucilage is produced and the unsuspecting insect is trapped. The tendrils detect the presence of the prey and curl upwards and inwards to close the trap. Eventually the whole leaf curls around the prey which is digested by enzymes secreted by glands in the leaf. Simple, elegant and deadly.
There is a second species, Greater Sundew (D. anglica), which is found in similar habitats and has more elongated leaves.
The Oblong-leaved Sundew (D. intermedia) has also been found in the islands, but can only be reliably identified with care (Drosera (Sundew) Identification & Recording).
Butterworts
The Common and Pale Butterworts (Pinguicula vulgaris and P. lusitanica) are more elusive and can be difficult to find when not in flower. The long-stemmed, violet flowers of the Common Butterwort are quite showy for a small plant and give rise to the alternative name of Bog Violet (Mothan) This is one of the most important plants in Hebridean folklore with properties that range from protection from fairies to love and good luck charms. The English and Scots names (Earning-girse – curdling plant and Ostin gorse – cheese plant) refer to it’s ability to curdle milk and use in making cheese.
As the name implies, the Pale Butterwort, is more anaemic in colour and can be difficult to spot even when in flower.
In both species, the upper surface of the leaves have slime-secreting glands which create a sticky surface. Any small insect landing on the leaf becomes stuck to the surface and is trapped as the leaves slowly curl inwards and begin to digest the prey.
Bladderworts
The Bladderworts (Utricularia species) are the least well know of the trio, although they are members of the same family as the Butterworts (Lentibulariaceae). These free, floating aquatic plants skilfully hide their carnivorous appetites. The most sophisticated of our carnivorous plants they use powerful suction to catch their prey and have a trap that is faster than the blink of an eye. They have no roots or leaves, but consist of long, thread-like stems covered in tiny filaments that act as leaves and have bladder traps at their tips. Once a small insect or invertebrate touches trigger hairs on the trapdoor of the bladder, it snaps open. The bladder is empty, so water, and anything nearby is sucked in with an acceleration of over 600 times the force of gravity! The trapdoor then quickly shuts again trapping the insect within to be slowly digested.
Fascinating plants, but difficult to identify. There is a key in New Flora of the British Isles (2019 fourth edition).
