Drosera, commonly known as the sundews, is one of the largest genera of carnivorous plants, with at least 194 species. Both the botanical name (from the Greek drosos and the English common name, sundew refer to the glistening drops of mucilage at the tip of the glandular trichomes (hairs) that resemble drops of morning dew.
Charles Darwin, the great naturalist who was prominent in developing the theory of evolution conducted a lot of research into Drosera and through this research was able to confirm carnivory in plants. In a letter written in 1860, Darwin said “… at the present moment, I care more about Drosera than the origin of all the species in the world.” Go Sundews!
Sundews originate from warm climates such as those found in South Africa, Australia, New Zealand and South America where frost rarely occurs. They can be found growing natively on every continent with the exception of Antarctica. Their habitats are mostly open fields where they can get lots of sunlight and they also grow among grasses, weeds and trees. Different species of sundews vary greatly in size and form. At least 23 of these sundews are endemic to the Western Cape including the Cape Sundew (D. Capensis).
HOW DO THEY GROW?
Most sundews are perennial herbs. This means they can live for more than two years. A few species are annual herbs or dwarf shrubs. While each type of sundew has its own unique characteristics, they tend to form an upright, stemless rosette of blades (laminae) that are densely covered with clear droplets of a sticky, viscous fluid (mucilage) used for trapping insects. In spring and summer, healthy sundews produce odourless, nectarless flowers that do not rely on insects for pollination rather relying on self-pollination.
Sundews lure, capture, and digest insects using a sticky mucilage (glue) that covers the surface of their leaves. The captured insects supplement the poor mineral nutrition of the soil in which the sundews live and supplies the plant with essential nutrients required for the plant to grow and flourish.
The leaves of the sundew have evolved into sticky ‘flypaper’ type traps that are covered with ‘tentacles’. On the tip of every tentacle there is a nectar gland which produces a sticky globule (mucilage) containing digestive enzymes. When an insect lands on the leaf they get stuck on the dew. As they struggle to free themselves, the tentacles of the sundew start to wrap around the insect through a complicated biological process. The insect eventually suffocates or dies from exhaustion and the digestive enzymes on the sundew then absorb the required nutrients from the dead prey.