Here’s why Bellingham’s Scudder Pond is such an unnatural color

Editor’s note: This story was updated Feb. 1 to reflect that no toxicity was found the water.


Nature is putting on an uncommon show at Scudder Pond, where the pond’s surface is a bright rusty-pink.

The unusual hue has stirred wonder as well as concern from nearby residents and visitors ambling through the 2-acre nature preserve of ponds and wetlands at the northeast end of Bellingham’s Whatcom Falls Park. The color covers about a third of the pond.

What’s causing it?

An aquatic fern called Azolla, according to Sara Brooke Benjamin, the environmental coordinator in the Natural Resources division of the city’s Public Works Department.

She went there recently to check it out.

“Multiple passersby stopped to ask about the plant and expressed concern,” Benjamin said in an email to The Bellingham Herald. “Folks explained that they have been walking that trail for years and this is the first time it has turned red. One person expressed concern that it was related to pollution and someone else was concerned about mosquitoes breeding in the pond.”

Neither is the case, according to Benjamin:

The freshwater plant isn’t caused by pollution. It treats it.

“It does not increase mosquitoes, (it) actually suppresses them,” she said.

And, it isn’t an invasive plant, but “a fairly rare and beneficial native plant,” Benjamin said.

As for how the water fern got there, Benjamin didn’t know but guessed that it was “carried in by some waterfowl.”

Scudder Pond.jpg
Azolla, a water fern, is turning Scudder Pond at the northeast end of Bellingham’s Whatcom Falls Park a bright rusty-pink. Robert Mittendorf The Bellingham Herald

The Whatcom County Health Department tested the water this week to find out whether the plant was making the pond toxic, according to spokeswoman Melissa Morin.

It wasn’t, according to preliminary results.

But, out of caution, a sample was sent to the King County Environmental Lab for toxin analysis, Morin said.

That lab found no toxicity in the water, Benjamin told The Bellingham Herald on Friday.

Also called Scudder’s Pond, the property is in the Lake Whatcom watershed.

Nature preserve

It is described as a nature preserve in an urban setting, and can be accessed from city of Bellingham trails off Electric Avenue and Alabama Street.

The area has a diversity of migratory and breeding birds, mammals and other wildlife. They include beavers, mallard ducks, red-winged blackbirds, buffleheads, black-crowned night-herons and great blue herons, according to North Cascades Audubon Society.

Plant life at Scudder Pond includes cattails, sedge and lady’s thumb.

The area also is a stop on the Great Washington State Birding Trail.

As for the plant itself, it’s an interesting one that isn’t common in the area, said T. Abe Lloyd, a member of the Washington Native Plant Society.

“I have spent a lot of time tromping around in Whatcom County wetlands and I have never seen it,” said Lloyd, an adjunct professor for Western Washington University who teaches natural history, wetland plant identification and ecology.

Fern is green in summer

It is a fern that floats, Lloyd said. The plant is usually green during summer. When the weather turns cold, the plant turns red.

“If you look closely, you can see that each leaf has dozens of small, shingle-like segments. It is commonly called mosquito fern and is thought to grow densely enough to keep mosquitoes from laying their eggs in water bodies,” he said in an email to The Herald. “The plants also fix nitrogen and are used as a living fertilizer in rice paddies.”

The fern is rare further north, Lloyd said.

“In British Columbia, there are only around 10 populations known and it is listed as a threatened species by the Canadian government,” he said.

As for how it got into Scudder Pond, that’s hard to say.

“It could have been brought in on the feet of migrating ducks,” Lloyd said. “I have heard it is sometimes sold in the aquarium trade, so perhaps someone introduced it to Scudder when they cleaned out their fish tank. Fortunately, it is a native species.”

Kie Relyea has been a reporter at The Bellingham Herald since 1997 and currently writes about social services and recreation in Whatcom County. She started her career in 1991 as a reporter and editor in Northern California.