Vermont's Dry Summer Spurred Blooms Of Rare Plants Along Lake Champlain

Nov 11, 2016

Lake Champlain water levels approached record lows this summer, which exposed acres of beach sand that would normally be underwater.  This allowed some rare — and a few endangered— species of sand-dwelling grass plants to blossom, some of which may have lain dormant for decades.

On a recent blustery fall day on the lakeshore, two botanists from Vermont Fish and Wildlife set off to survey for rare plants on newly-exposed sand just north of where Winooski river drains into the lake.

"Where we're standing right now, we would normally be under a few feet of water," says Aaron Marcus, a botanist who works part-time for the Fish and Wildlife department.

Along with long-time state botanist Bob Popp, Marcus has been finding and cataloguing these rare dry-weather-induced bloomers. 

The first rare native plant we run into, we literally walk through.

"Creeping Lovegrass, it's forming a massive carpet," says Marcus, describing the knee-high, almost furry plant. It looks almost like a mat of underwater lakeweed that's exposed, though the leaves have gone brown after summer's end.

"It doesn't look like it could really be a rare plant, but it really only grows in places when the water draws down," Marcus says.

The plants seem to know from environmental cues when the drought comes early enough in the season that they will have time to grow and produce their own seeds.

State botanist Bob Popp explains that this annual plant, like many of these rare plants, has seeds that are only triggered to germinate after they experience a dry period for a certain length of time. Otherwise, the seeds can lay dormant for years — decades even — waiting for the right conditions.

And the plants seem to know from environmental cues when the drought comes early enough in the season that they will have time to grow and produce their own seeds, says Popp.

"Because we have this sandy muddy substrate exposed, and it's been exposed for a long enough period that not only can they germinate, they can also flower and set seed," says Popp.

Popp says it's hard to know precisely what environmental conditions trigger the some of these rare plants to sprout, because they could be sending up shoots in other years, but not having a long enough growing season to produce flowers.

"There may be other years where it gets down low enough that the seeds germinate, but they might stay vegetative," says Popp. "And identifying these vegetatively, as you could tell, is, boy, there'd be a lot of head scratching and saying, 'What the heck is that?'"

Without seed pods and flowers, lots of these rushes and sedges look alike, even to an expert like Bob Popp.

This photo of the Wright's Spikerush was taken this summer, when it was lush and green. Scientists aren't sure why, but some of the plants grow full and upright like this one, others stay more flattened to the ground.
Credit Aaron Marcus / Vermont Fish and Wildlife

Then, without any fanfare, Marcus spots what might be the rare Wright's Spikerush. The group huddles around the tiny little rush — the plant is about the size and shape of a crab-grass whirl that grows between pavements cracks.

Popp explains that to confirm the plant's identity, we need to open its tiny seed pods and examine the seeds like specks of cookie crumbs.

"What we need to do is dissect that little thing and look at it with a hand lens … without it blowing away," says Popp. The botanists break open the tiny pods to examine the millimeter-wide seeds. These seeds have what looks a bit like a miniscule version of a cap on an acorn on top, which is called the tubercle.

"Yup, these ones are the Wright's spike rush," Marcus confirms.

The Wright's spike rush is globally rare. There are fewer than 30 sites known globally for the species — and most of them are in Vermont, on Lake Champlain and the Connecticut River.

Bob Popp, the state botanist with Vermont Fish and Wildlife, uses his hand lens to inspect a rush's seeds for identification. Without the seeing the seeds, some rushes are impossible to distinguish from one another.
Credit Kathleen Masterson / VPR

After confirming the plant's identity, Marcus notes its GPS location and scoops some soil into a bag from next to the plant.

"We're cooperating with a researcher from the New York Botanical Garden, who is trying to figure out the distribution of this plant," says Popp. "And he thinks one of the key components is the substrate texture, so he wants us to collect sand where find this plant."

Popp says they are also collecting from south-facing beach locations that seem ideal for the rush, yet where they don't find it. The idea is to see if there is some special soil properties the plant favors.

Lake Champlain water levels measured in Burlington show the lake approaching a record low this year. It got down to 93.5 feet in October, and the lowest level ever recorded was 92.6 feet in December 1908.
Credit U.S. Geological Survey

And all the data about the rare plants they've surveyed this summer is being entered into an online database, noting the GPS location of each. 

Most states and Canadian provinces track their findings in the same format, creating fairly comprehensive  documentation across the continent.

So when it comes to finding these plants on these Champlain beaches, the botanists can say with reasonable certainty just how long its been since they've been spotted. 

This year, the globally-rare Wright's Spikerush and the forest floodplain water purslane are two that have cropped up in record numbers, and grown long enough to produce seeds.

Acres of additional sandy beach are exposed along Lake Champlain near the Winooski River delta.
Credit Kathleen Masterson / VPR

This report comes from the New England News Collaborative: Eight public media companies coming together to tell the story of a changing region, with support from the New England News Collaborative.