Garlic mustard vs. spring flora … Part one: The problem

During the past 10,000 years, after the glacier retreated, leaving barren rock and rubble, a complex ecosystem dominated by oaks and hickories developed in Illinois and the Midwest.

Along with the trees, a marvelous garden of wild flowers bursts forth in a showy display each spring. From the first promising days of March through the warmth of May, the forest floor is dotted, carpeted and finally blanketed by mounds and rivers of lacy green punctuated by many of the following: nosegays of pastel hepaticas, pure white bloodroot, nodding trout lilies, perky toothwort, red and white trilliums, frothy anemones, shy violets, dramatic Solomon’s seal, miniature forests of may apples, and rich, pink wild geraniums. When the trees fully leaf out, most of this breathtaking array has completed its cycle and disappears for another year.

But we’re losing this. Quietly, gradually, so that it’s a barely perceptible change. While the forests themselves are in decline, spring flora within those remaining are threatened. Garlic mustard, a formerly innocuous plant, can displace the rich, diverse population of natives within a decade. A garden can become a bleak monoculture if untreated.

Garlic mustard is an alien weed, brought here from England for kitchen gardens. The leaves are bland but nutritious, the seeds are spicy, and it has been occasionally used for medicinal purposes as have many other herbs. Being alien, it has no natural enemies. It expands rapidly, producing up to an incredible 100,000 seeds per square meter, which is viable for at least seven years.

Garlic mustard was first observed in a natural area in Cook County in 1918. By the late 1980s, its population exploded. It is now recognized as a serious threat to spring flora throughout the Midwest. It remains green through winter, continuing to grow when temperatures are above 35 degrees, and grows more rapidly in spring before natives have sprouted. Less competitive plants are shaded, becoming weak and spindly and eventually dying.

Garlic mustard’s explosion is a local example of how centuries-old natural balances are upset by human activities. In natural communities, such as oak-hickory forests, many native plant species are adapted to low levels of nitrogen. Excess nitrogen can reduce plant diversity. It is one of the key factors in the slow death of trees in the eastern United States and Germany’s Black Forest, and in the decline of European heathlands. Garlic mustard is a type of plant that responds favorably to excess nitrogen.

Human activities, including fossil fuel consumption for transportation and power and modern agricultural practices, have doubled the amount of nitrogen available for uptake by plants. These sources now exceed the global supply of fixed nitrogen from natural processes. Some scientists believe implications may be as serious as those of excess carbon in the atmosphere.

As fossil fuel-dependent transportation systems spread globally and more food is needed to feed the burgeoning world population, levels of available nitrogen are likely to increase. More efficient practices could reduce emissions. Increased use of renewable energy would dramatically limit emissions.

While there are successful management strategies to control garlic mustard, it is a battle that must be waged repeatedly to be won.

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