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Jun 02, 2023

Robert Miller: Do we need to battle the invasive garlic mustard?

Barnaby Taylor of Darien helps pull up garlic mustard plants at the Selleck's

Barnaby Taylor of Darien helps pull up garlic mustard plants at the Selleck's Woods & Dunlap Woods Nature Preserve cleanup on Sunday, April 18, 2021.

I’m resigned to losing a fight I fight against my yard's invasives — multiflora rose and oriental bittersweet, autumn olive and the burning bush popping up near my driveway.

But come spring, there's another noxious plant forcing itself on my consciousness — garlic mustard.

From being a small-time bother to a stalky tidal wave, garlic mustard now grows in every spare corner of the place. I pull it up randomly as I’m walking around, or in concentrated bursts of cleaning up THAT garden spot.

Since each of these biennial plants produces hundreds of seeds and those seeds can sit dormant and happy in the ground for years before sprouting, garlic mustard ain't leaving anytime soon.

Nor am I alone.

Garlic mustard — a non-native invasive plant — has been crowding the North American landscape for over a century. Brought to the New Word from Europe as an herbal and medicinal plant in the mid-1800s, it's now found across the continent, with only the American Southwest being spared.

Its Latin name is Alliaria petiolata. It has several colorful folk names — poor man's mustard, hedge garlic, jack-by-the-hedges. I, myself, have used other colorful Anglo-Saxon words when dealing with it

There is a debate about what to do with it — pull it or leave it be. Because it's edible, you can, if you want, make sauces like garlic mustard pesto with it.

On the pull it up corner are people like Kathleen Nelson of New Milford, a member of the Mad Gardeners, a Litchfield County group of gardeners and a dedicated foe of invasives.

"Personally, I’ve been pulling it up and I’ve been doing so for many years,’’ Nelson said. ‘I check my yard, starting in mid-May.’’

Nelson said she's helped her son battle garlic mustard on land that was overrun with it. After a decade of yanking it up, she said, there's only about a half-dozen garlic mustard plants on the property.

She is still vigilant.

"You don't ever think it's gone,’’ she said.

Likewise, Bill Moorhead — a botanist and plant science ecologist with the state Department of Energy and Environmental Protections’ Natural Diversity Database program — worked in 2014 with volunteers to clear a floodplain in Avon of Japanese barberry.

They got rid of the barberry. But in places where there was a mosaic of barberry with other plants, garlic mustard sprang up and blanketed the forest floor.

"I pulled up 6,000 garlic mustard plants the first year,’’ Moorhead said. ‘Then it went down by 2,000 or so each year following until we got to the point where there was only a handful left.’’

The rationale for removing garlic mustard is it grows faster in the spring than other native plants in the forest and shades them out. It's also thought that the plants release chemicals into the soil that disturbs the underground fungal network that connects plants life.

And according to Bernd Blossey, none of that is true.

Blossey is a conservation biologist and a professor of natural resources and the environment at Cornell University in Ithaca NY. He has been studying invasive plants like garlic mustard for more than 25 years.

Blossey said what he's found is that what's keeping native plants down in the woods is overgrazing by deer. Garlic mustard, he said, doesn't interfere with native plant growth at all.

"Native plants will do very well if you exclude deer,’’ he said

He's also found a connection between garlic mustard and another invasive species — earthworms

The worms we see when we dig up our gardens aren't native worms. They’re European earthworms, brought here by settlers in the 18th century when the horticultural trade between the New World and the Old World began. Or they’re Asian jumping worms, which came to North America a century later.

Blossey said it is a certainty that garlic mustard flourishes where worms flourish as well. It needs them. While ecologists don't understand why this connection exists, it may have to do with microbial changes in the soil, he said.

He's also found garlic mustard has its own cycle. It shows up, it flourishes, then, after a few years, fades away, leaving only a few plants hanging on. Pulling it up only prolongs the cycle

This is because garlic mustard, growing in the same spot, exhausts itself, using up the soil nutrients it needs.

"If you have a garden, you know this,’’ Blossey said. ‘You don't plant potatoes on the same spot every year.’’

Contact Robert Miller at [email protected]