Each spring in Herrontown Woods, from April through May, we take part in the Great Garlic Mustard Pull. That's the effort, replicated in yards and nature preserves throughout the eastern U.S., to pull garlic mustard
(Alliaria petiolata) out of the ground before it goes to seed. This post explores the logic, toils and unexpected pleasures, as well as the strategies that can make this annual gardening task easier each year.
We pull this nonnative invasive plant, with its aroma of garlic and mustard, because the alternative is too much to bear. Left unchecked, garlic mustard can take over a woodland or garden, altering soil chemistry and smothering native species.
People pulling the flower stems are surprised to learn that other, lower-growing plants coating the ground are also garlic mustard. Two very different forms of the plant are present at the same time. Unlike most herbaceous plants that are either annuals or perennials, garlic mustard is a biennial. That means it grows a rosette the first year, storing energy in its roots--energy that will be used the second year to send up seed-bearing stalks. After the stalk blooms and the blooms turn to seed, the plant dies, leaving copious seed for future generations.
Gardeners are often fooled at first into leaving garlic mustard be. The flowers are modestly attractive, and as they fade and turn into siliques packed with seeds, the plant too fades politely into the background. But wait a month or two, and the flowering stems turn brown, populating the garden with skeletal remains. By the time the gardener notices this blight, the seeds have already dispersed.
Much is made of the plant being edible. Young leaves can be used to make pesto and other dishes. Our friend Kirsten used it to make delicious deviled eggs. But in most situations, the plant's powers of proliferation quickly overwhelm people's appetites.
And so we pull, and pull. That's Herrontown neighbor Philip Smit in the photo. The aim is to get every last one, to ultimately exhaust the soil's supply of seed. Only with zero tolerance will the task get easier year to year. Here is where technique and timing come into play. If you pull hastily, or when the soil is dry, you may get the stem but not the root. This is an incomplete victory. That root will sprout new seedstalks that then too must be pulled. So we "grab low and pull slow", ideally pulling after rain has softened the soil, and return a week or two later to check for any resprouts.
And what to do with the pulled stems? Bagging them is a lot of work and wastes energy to have them hauled away. This year, we've been putting them in trash bins, then rolling them to a pile. In case any of the seeds mature, the pile is located where the seeds won't wash down the hill, and any seedlings will all be in one spot.
I've heard stories of gardeners who pulled year after year, and yet the garlic mustard continued to sprout anew. Where would the seed come from? We speculated that erosion from heavy rains, or the diggings of squirrels, could expose long buried seed.
But another cause could be these miniature plants I've been finding. We pull the bigger plants and think our work done, but no. A second and even a third pass is needed over the course of weeks, with an eye out for these tiny plants.
There can be pleasure in the task. These two visitors to the preserve joined in one day. Kids, too, take to the pulling, seeking out the white blooms as if it were an Easter egg hunt.
We're grateful that some students from Princeton University's Outdoor Action--Will Aepli, Quest Starkey, and Zach Duscorsky--worked with Ben Schaffer and me to clear garlic mustard from the Veblen House grounds and the Barden. Inge Regan, Moss Gordon, Ninfa and Andrew have helped with a larger patch in another woodland we're restoring.
Invasive species can seem an impossible challenge, but if the invasion is caught early, and the garlic mustard is completely removed year after year, even the task of protecting 230 acres of public open space at Herrontown Woods and Autumn Hill Reservation becomes doable, with some satisfaction and even pleasure in the task.
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