Eugene Weekly : It’s About Time : 12.3.09

By David Wagner

This year is a purple pond year. Right now a couple of ponds on either side of Delta Highway are covered with a pink-purple layer of tiny plants. This is a living film of Azolla, the mosquito fern, a floating aquatic with leaves smaller than the head of a pin. In the summer Azolla is green, like the duckweed it grows with. Judging from foraging behavior, Azolla is eaten as avidly as duckweed by the resident mallards.

Most years it is present in low numbers and is lost in the green of the more abundant duckweed. Then, every few years there is a flush of Azolla that overwhelms the duckweed. When the bigleaf maple leaves turn yellow, the Azolla turns the whole pond surfaces a brilliant, wonderful purple. You can’t miss it!

Admiring the purple ponds I notice blackberries being cut around the East Delta Ponds in preparation for plantings of native vegetation. It is a monumental project because the blackberries covered acres of gravel mining wastes that have never seen natural cover. I anticipate wonderful changes to come.

 Many organizations around town are doing restoration work. We can help. Winter is a great time to volunteer to work on habitat restoration because heavy clothes help protect from the thorns of the wicked blackberries. I have personally cut many a blackberry at the Mount Pisgah Arboretum, delighted to watch wildflowers replace them the following spring. A great solstice gift would be a couple of days helping out a restoration group.

David Wagner is a botanist who has worked in Eugene for more than 30 years. Every year he makes the Willamette Valley Nature Calendar, available this month at Down to Earth and the UO Museum of Natural and Cultural History. Reach him at fernzenmosses at


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