A sundew looks as though morning dew has settled on every hair of its leaves, even in dry weather. Those sparkling beads are not ordinary dew. They are sticky mucilage made by the plant itself. When a small insect lands, the glue holds it while nearby leaf tentacles slowly bend toward the struggling visitor.
Are the sparkling droplets actually water?
The droplets contain water, but they also contain sticky compounds that make the liquid cling to a tiny insect. Each red or green stalklike tentacle ends in a gland that produces this secretion. Sunlight catches the beads like miniature glass ornaments, giving the plant its English name. If a leaf still sparkles in the middle of the day, that does not mean it was watered recently.
How does a sundew trap an insect?
A gnat, fruit fly or another small arthropod may be attracted by the shiny surface and land on the leaf. Its feet and wings stick to the adhesive droplets. As the insect struggles, it can contact more tentacles. In many sundews, the tentacles bend inward; some species, including the Cape sundew, also curl part of the leaf around the prey. This is a slow response compared with the abrupt snap of a Venus flytrap.
The trap’s effectiveness is not based on strength or speed alone. One droplet can become several points of contact, making escape harder. The leaf’s movement brings additional digestive glands close to the insect. Depending on the species, prey size and temperature, the process can take many minutes or hours rather than an instant.
How does it digest what it catches?
After capture, glands release enzymes that break down parts of the insect. The plant absorbs dissolved nutrients through leaf tissues. The remains of hard external structures may stay behind after feeding. This is not exactly like a human stomach, and the plant cannot swallow its prey. Its leaf serves as both the sticky net and the nutrient-absorbing surface.
Why would a plant eat insects at all?
Sundews photosynthesize to make sugars using sunlight, just like other green plants. Capturing insects helps them get nutrients such as nitrogen and phosphorus, which are scarce in the acidic bogs and other poor soils where many sundews grow. Insect capture supplements a food-making process driven by light; it does not replace it.
Different kinds of sundews live on several continents and vary greatly in shape. Some resemble compact rosettes, while others have narrow, upright leaves. The close-up photograph here shows a Cape sundew, Drosera capensis, a South African species commonly grown as a carnivorous houseplant.
Can you grow a sundew on a windowsill?
Many cultivated sundews prefer bright light, consistently moist but low-mineral growing conditions, and a suitable peat-free or mineral-poor carnivorous-plant medium according to the species. Rainwater, distilled water or another appropriately low-mineral source is often preferred over hard tap water. Ordinary fertilizer-rich potting mix can be harmful. Species differ in their temperature needs and dormancy cycles, so identify the plant before choosing a routine.
Avoid repeatedly poking the droplets to watch them move or adding food scraps such as meat. A healthy sundew does not need a steady human-supplied diet of insects. For a family observation, use a magnifying glass to study the little beads and draw the leaf’s shape without disturbing a trapped animal.
Frequently asked questions
Is sundew glue harmful to people?
The tiny droplets are adapted to catch small insects; they are not a human-sized trap. Still, do not rub plant secretions into eyes or mouths, and wash hands after handling plants.
Why are the droplets disappearing?
Insufficient light, unsuitable water, dry conditions or general plant stress can reduce visible mucilage. Check care requirements for the species rather than assuming it needs insects.
Do sundews snap shut like Venus flytraps?
Usually not. Many sundews curl slowly, whereas Venus flytraps use rapid snap-traps activated by trigger hairs. Both are carnivorous plants, but their methods differ.
Learn more
The United States Botanic Garden describes the adhesive and moving traps of sundews. Compare another touch-responsive plant in our guide to sensitive-plant leaf folding. Sundews and the sensitive plant use different structures and serve different purposes.
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