Naturespeak 

Sundews: Tiny but deadly

By Kristina Swerhun and Bob Brett

Whistler Naturalists

Did you think you had to be somewhere tropical to encounter a ferocious carnivorous plant? Well think again, we’ve got one right in our backyards (well, our bogs to be exact). Unlike most plants, sundews supplement their diet by digesting insects.

Sundew leaves are their most striking feature. The upper surface of the leaves is covered with reddish, glandular hairs tipped with a sticky, glutinous secretion that attracts and traps insects. It isn’t a coincidence that insectivorous plants like sundews are found in bogs. Bogs lack in many of the essential nutrients a plant requires. Sundews solve this problem by adding nutrient-rich insects to their diet.

The sundew diet includes small insects like mosquitoes, gnats and midges attracted by the colour of the sticky drops at the leaf edges. Once an insect is trapped, the leaves bend inwards and the insect comes into contact with fine, inner hairs. Enzymes then assimilate the insect’s juices, the leaves uncurl, and the dry parts of the insect (the exoskeleton) blow away. The attractive, glistening "dewdrops" reappear, and the innocent-looking sundew is again ready for business.

Two species of sundew live in Whistler’s bogs. Round-leaved sundew ( Drosera rotundifolia ) is the more common; great sundew ( Drosera anglica ) has much narrower and longer leaves. Both require a bit of work to find since they are so small – usually less than 10 centimetres tall.

First, locate a peat bog – a perfect one is in the Nature Reserve, just south of the Emerald Forest. Put on your rubber boots and proceed until your feet are squishing into the bog, then look down. Get low enough for your knees to get wet, then drag your nose (or at least your vision) along the ground surface. Once you find the first one, you’ll get the search image and will miraculously see dozens surrounding you.

In comparison to its leaves, a sundew’s white flowers are pretty run-of-the-mill. And you need to be a bit lucky because they only open on sunny days around this time of year.

More information on sundews comes from Lewis J. Clark, author of the floral tome "Wildflowers of the Pacific Northwest". Sundews are widely distributed throughout North America and Europe and were a favourite of Charles Darwin. While not writing about evolution and countless other topics, Darwin found time to produce a book on insectivorous plants, of which over 300 pages were devoted to sundews.

Darwin explored the exquisite precision of these tiny plants and discovered that the tentacles (really modified hairs) enclosed within each drop of sticky liquid were able to discriminate between potential food and anything else. An object containing protein, such as an insect, stimulated a quick response from the tentacles. Anything without protein barely got a rise. Darwin, apparently with endless time on his hands, tested the sundews’ sensitivity with an incredibly small piece of a human hair and found even that amount of protein enough to elicit a response.

To learn more about sundews and other inhabitants of our bogs and wetlands, join the nature walk on Wednesday night (see below).

Upcoming Events:

Wetland Nature Walk, 6:30 p.m. Wednesday, June 29 th . Join wetland plant experts Adolf and Oluna Ceska on a tour of the wetlands in Whistler Wildlife Reserve. Veronica Woodruff will also be on hand to talk about fish and other freshwater creatures. This is a joint event of the Whistler Naturalists, AWARE, and the RMOW. Meet at the base of Lorimer Road, by the Catholic Church.

Dragonflies and Birds Nature Walk, 6:30 p.m. Wednesday, July 6 th . Another out-of-town expert, Derrick Marven, will lead a walk focusing on dragonflies and birds, but which will likely veer into anything from the natural world we encounter. This walk will also assemble at the base of Lorimer Road, by the Catholic Church.

Dragonfly and Butterfly Survey, July 4 th to 7 th . If you already know about dragonflies and butterflies, or would like to know more, consider joining Derrick Marven’s survey for an hour or a day. Like the Ceskas, Derrick is here to catalogue Whistler’s biodiversity as part of the Whistler 2010 Biodiversity Project.

For more information on these events, contact Bob Brett (932-8900; Bob@SnowlineResearch.ca).

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