Chapter 3
Eat the Pushy Invasive Plants
Like earlier migrants, modern families sometimes carry seeds of their favorite plants with them when they move to a new place. When they plant the seeds, sometimes the introduced plants go rogue, escaping over the garden fence. Other plants arrive uninvited. Their seeds might cling to a traveler’s clothes or shoes, or they may hitch a ride along with a ship’s cargo or ballast water (water a ship carries to maintain balance and stability while sailing). The seeds may come with birdseed mix or travel in bags of potting soil or garden seeds.
When introduced plants spread aggressively, they compete with native species for sunlight, water, and space to grow. Estimates vary, but biologists have so far determined that up to 20 percent of introduced plants around the world are invasive and threaten biological diversity in the habitats to which they have been introduced.
Climate change also influences how—and whether—invasive plants expand their ranges. For example, warmer temperatures year-round and the arrival of earlier springs can give quick-blooming invaders an edge over slower-blooming natives, points out Elizabeth Wolkovich. She is an ecologist at the Biodiversity Research Centre at the University of British Columbia in Vancouver, Canada. When invasives bloom earlier than native plants, they capture the lion’s share of nutrients, water, and light, making it more difficult for native species to thrive.
Invasive plants, such as these kudzu vines, threaten biological diversity. Because they grow so aggressively, the plants hog sunlight and water and space, forcing out native species. Biological diversity is key to the health of any ecosystem. Kudzu leaves and flowers are edible!
The Plant That Ate the South
Kudzu (Pueraria montana) has blanketed the American South, pushing its way into fields and forests, covering everything in its path. This vining member of the pea family is native to China and Japan, where it has been used for centuries as a food and fiber crop. Kudzu first came to the United States as part of the Japanese exhibition of the 1876 Centennial Exposition in Philadelphia, Pennsylvania. By the end of the century, southern gardeners were importing kudzu seeds and planting the ornamental vine to shade their porches.
In the 1930s, the USDA gave kudzu plants to southern landowners, hoping to reduce soil erosion caused by poor farming practices and deforestation. The agency even offered farmers an incentive of eight dollars an acre to plant kudzu. The USDA told farmers that kudzu plants would add nitrogen to improve the soil, and that it was good for livestock to eat and for making hay.
What they didn’t realize was that kudzu grew too well. During the heat of summer, kudzu vines can grow 1 foot (0.3 m) per day, extending their reach 60 feet (18 m) over a single season. The vines smother trees and other plants in their path under a thick mat of leaves. By 1953 the USDA had stopped promoting kudzu because of its invasive tendencies. However, kudzu continues to expand its range, crowding out native plants and interfering with farming across the South. And as Earth’s climate warms, northern states are becoming warmer and more hospitable to kudzu. The invader is showing up in Massachusetts, New York, and parts of southern Ontario, Canada.
A creative way to deal with kudzu? Eat it! Kudzu leaves, gathered when the plant is young, can be served in salads, steamed as greens, or baked into quiche. Kudzu leaves are big so they also work perfectly as sandwich wraps. You can boil or bake kudzu roots just as you would potatoes. As for the flowers, they are fragrant and smell something like grapes. They can be batter-fried, dried for tea, or steeped in hot water to impart their flavor to jelly.
When foraging for kudzu in the wild, pay attention to the surrounding vegetation. Poison ivy may grow in the same habitat, and because both plants have three leaflets, they can be confused. But the petioles (leaf stems) of kudzu plants are covered with tiny hairs, while poison ivy petioles are smooth. Also, kudzu has purple flowers that grow in a showy cluster as long as 8 inches (20 cm). Poison ivy flowers are tiny, with green or white petals that form a star, and yellow centers. Just remember: When in doubt, don’t eat it. And if you’re harvesting edibles in poison ivy territory, wearing gloves is a good idea.
Beauty Gone Beastly
Japanese knotweed (Fallopia japonica), native to Japan, China, and the Korean peninsula, was introduced to the United States in the late nineteenth century. Gardeners liked its heart-shaped leaves, sprays of tiny white flowers, and tall, sturdy bamboo-like stems. Americans started planting Japanese knotweed for landscaping as well as for erosion control.
Japanese knotweed can grow up to 6.5 feet (2 m) tall and 65 feet (20 m) wide. Its shallow roots force their way through cracks in patios and concrete walkways, and into walls and floors. They can be very difficult to manage, so think before you plant them. However, if you find them in the wild, they are edible.
Like kudzu, Japanese knotweed spreads quickly, forming dense thickets that shade and squeeze out native plants. Since the year 2000, the International Union for Conservation of Nature (IUCN) has maintained a list of the world’s worst invasive species. Japanese knotweed is so aggressive that it has made the top one hundred on the list, known as the Global Invasive Species Database. In wet areas, Japanese knotweed takes over stream banks, crowding out trees that provide vital shade for fish and wildlife. It turns out that knotweed isn’t good for erosion control either. Its roots grow too shallow to hold down soil, and the plant dies back in the fall. That leaves stream banks more susceptible to erosion, not less.
So what is redeeming about this invasive? You guessed it. Its tender young shoots are crunchy and tasty—tart, like rhubarb. Some people simply clean, slice, and toss them into a salad. Others prefer Japanese knotweed shoots grilled, stir-fried, sautéed, pickled, or baked into pie with strawberries.
The best time to harvest Japanese knotweed shoots is early spring, when they first poke out of the ground. Don’t worry about overharvesting, but do be sure to pick the entire plant, including all the roots. This plant regrows from the tiniest bit of rhizome, so be sure not to leave any behind in the ground, or even lying on the ground.
Into the Woods
European colonists brought garlic mustard (Alliaria petiolata) to North America for food. They also mashed the roots to make poultices (pastes) for colds and bronchitis. Garlic mustard flowers have four petals, and the seeds of the plant are in slender pods. The leaves usually have a garlicky flavor, though this depends on the plant’s maturity and location. The leaves of plants in shaded areas tend to be very mild, and the leaves of older plants tend to become bitter. The entire plant is edible. The greens are delicious in stir-fries, frittatas, soups, and stews. You can also add finely chopped garlic mustard leaves to mashed potatoes, biscuit and tortilla dough, or as an ingredient in pesto. Raw leaves and flowers go well in salads and sandwiches but should be eaten in moderation. Some cooks grate the roots and mix them with mayonnaise to make a dip resembling horseradish sauce.
Please, Eat the Invaders!
Don’t worry about picking too many garlic mustard plants. And feel free to yank them out by the roots. These plants are such aggressive invaders in northern forests that it’s almost impossible to stop them from spreading. For example, a single garlic mustard plant can produce thousands of seeds, which remain viable in the soil for five years or longer. Once established, these plants tend to dominate the forest floor, spreading 20 to 120 feet (6 to 37 m) in a year. Deer don’t like the taste of garlic mustard, so they avoid them, which also facilitates their spread.
Garlic mustard engages in chemical warfare against native plants. The mustard roots produce chemicals that harm mycorrhizal fungi in the soil. Those fungi live in a symbiotic (helpful and interdependent) relationship with the roots of trees and other forest plants. The fungi help the other plants absorb nutrients from the soil. Without the fungi, fewer trees grow and the trees produce fewer leaves. This affects salamanders and other species that make their homes in the leaf litter, the layer of dead leaves on the forest floor. To control garlic mustard, conservation groups organize trail hikes and weed festivals where volunteers harvest garlic mustard by the bushel. So please, eat the garlic mustard! And the kudzu and the Japanese knotweed. Be an invasivore (invasives eater) pioneer. Eating invasive plants won’t eliminate them, but it can help control them.
Bees are key pollinators of flowering plants, including edible species. When you plant a garden, include native species that attract pollinators.
POLLINATION BETWEEN FLOWERING PLANTS OF THE SAME SPECIES
Three-fourths of Earth’s flowering plants and about 35 percent of all food crops require animal pollinators to reproduce. These pollinators include bees, butterflies, moths, beetles, birds, and bats.