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Picture: Second-year garlic mustard in bloom April 2006. Downtown Stamford CT. The red bug is an invasive European lily leaf beetle, lurking in the garlic mustard which is near some lilies. These beetles are harmful and should be hand-picked and destroyed. No predators: Even more unfortunately, part of the "invaders' edge" is the lack of predators. Garlic mustard, for example, has no known, significant local predators. Our insects won't eat it; even the white-tailed deer leave it alone unless they are desperate. By comparison, in its native Europe, some 60 or 70 insects eat garlic mustard, including some that don't seem to eat anything else. The local fauna doesn't tend to recognize the invader's leaves and roots as food, so the invader doesn't get munched up as often as the native plants. This gives the invader a competitive edge over the natives. As the invader pushes out the native plants, the native plant-eaters decline, and so do the birds, frogs, and other critters that feed on the plant-eaters. Our local plants have co-evolved with the local fauna and they are mutually dependent. It is said that when a single native plant species dies out, up to 30 other plants and animals may be adversely affected.

Pictures (above): Winter view of garlic mustard leaves, Jan 2003, Bedford Street, and a close up of the leaf texture and veins, December, 2005 Scalzi Park. Both Stamford CT. Pictures: close up of new, first-year leaves; second -year garlic mustard in flower. Stamford, CT 2004 How does it do it? The botany: Garlic mustard seedlings get their heads up early enough in spring to shade out the later-rising native plants. Thus, the garlic mustard seedlings get off to a good start, untroubled by competing seedlings or leaf-munching pests. By summer, the young plants form low circlets of leaves, known as "basel rosettes". The leaves are kidney shaped with a scalloped edge and a "quilted" texture. The leaves start out a pale, fresh green but darken with age. When new, the crushed leaves smell distinctly like garlic but this scent fades away by fall. The tap root doesn't grow straight down, it has a hooked shape or an "S"-shaped curve to it. The young plants stay green all winter, continuing to soak up the rays while the competition is dormant. The young garlic mustards stay low through the winter, taking advantage of the insulating snow, warmth of the earth, and winter sun. Then, in the second year, the plants shoot up 2� to 3�, with clusters with white (or pink) 4-petal, cross-shaped flowers in May. The bolting garlic mustard has so much stored energy that if you pull up a flowering plant, and leave it in the damp shade, it still can finish making its seeds. Garlic mustard is an "obligate bi-annual" in that it has to go to seed in its second year, whether or not growing conditions have been favorable. By mid-June or July, the second-year garlic mustard plants have died off, leaving only the dried stems and upright, banana-shaped seed pods characteristic of the mustard family. Picture: Second -year garlic mustard already in seed and starting to die. Hoyt Street Alley, Stamford, CT June 2006. Picture: Additional view of second -year garlic mustard already in seed and starting to die; close up of seeds. Hoyt Street Alley, Stamford, CT June 2006 How it spreads: Curiously, the experts aren�t sure how garlic mustard spreads. They know you can�t blame it on the birds or the wind. Each plant makes hundreds of seeds that remain viable for years in the soil's "seed bank". However, the seeds fall close to the parent, and none of our fauna eat the seeds, so it in not spread to other locations via droppings. It is known that garlic mustard is self-fertilizing so even if only one seed germinates, it can start a whole colony (or repopulate the colony that you just ripped out). It is also know that the seeds only do well in disturbed soil. Left undisturbed in a shaded forest, the garlic mustard population will reach a low-level equilibrium. However, should the surrounding ground be disturbed by, for example, ripping out a neighboring invasive plant, it's "Molly, bar the door". It is believed that culprits in spreading garlic mustard are humans and the white-tailed deer (that, in turn, have enhanced populations due to human activity). Both humans and deer help garlic mustard by disturbing ground along the forest's edge and the paths, allowing the garlic mustard to then take over. But how does garlic mustard move from site to site? Best guess is that the seeds cling to the fur, clothing, and tires of passing animal and human traffic. It is also believes that flood waters significantly spread the seeds, even though the seeds don�t float well. Pictures: Pulled garlic mustard plant, just about to flower in its second year; detail of its thick, energy-storing, hook-shaped root. If left along the trail in moist shade this plant could still flower and seed. Bartlett Arboretum, May 2006, Stamford CT. Chemical Warfare: What we're also finding out more and more about only too many invasive plants is that their arsenals include allelopathic (herbicidal) chemicals that inhibit the growth of other plants. In the case of garlic mustard, tests are showing that garlic mustard engages in, not one, but TWO forms of chemical warfare. First, is the straight forward, kill some of your neighbors with herbicidal chemicals that keep them from growing. Second, and much more scary, is that studies are showing that garlic mustard may interfere with mycorrhizal activity in native plants, including our precious hardwoods, leading the decline of the entire forest. Translated into English: There are tiny soil fungi that form a symbiotic (interdependent relationship) with certain plants. The fungi attach to the plants' roots and help the roots absorb nutrients from the soil; the plant, in turn, feeds the fungi what they need. Many plants die without their specific fungi and visa versa. Our native trees and shrubs are mostly mycorrhizal-dependent. However, garlic mustard, and many other invasive or weedy plants, don�t depend on root fungi. Studies have shown that mycorrhizal-dependent plants go into serious decline when planted near garlic mustard. Some say that the studies are not definitive. This is probably true; what's shocking to the lay person is just how little is actually known about the activity of the plants in our forests, natural or otherwise. Who stole the trillium? Anyone wandering the woods around here who's over the age of 40 can see with their own eyes that our precious woodland wildflowers of yesteryear are mostly gone. We still are blessed with spring beauties, trout lilies, toothwort, and a few other but so many plants -- lady slippers, trillium, hepatica, ginger, blood root, etc., are getting harder and harder to find, even in woods not overly used for humans recreation. Why? Some say it's the Norway maples. You have seen how their thick roots and dense shade kill your lawn; they do the same thing to the forest under-story. I'm sure that they are part of the problem; but there are fewer wildflowers even in Norway maple-free areas. Some say it's the white-tailed deer, eating everything is sight as they are driven into smaller and smaller areas by encroaching condos and McMansions. I'm sure that the deer are also part of the problem since the missing plants tend to be those which have a harder time getting started and are easily damaged. But I find some grasses and other edibles still left in the forest -- it's not stripped bare (yet). So could garlic mustard be playing a role in not only killing off the woody perennials (trees and shrubs) that are the forest, but also in the disappearance of the wildflowers? Getting rid of garlic mustard: There are similar-looking native plants, so first, get to know what the plant looks like. In spring and summer, check a crushed leaf for the tell-tale garlicky smell; year-round you can also check the first plant you pull for the hook in the tap root. Don't confuse the leaf with your local violets. Like all invasives and weedy plants, it is best to stay ahead of the curve. Any time that you see a few of a plant that doesn't belong, that's the time to root it out. What tends to happen, and this is true of garlic mustard, is a small, seemingly-innocuous colony will form and appear stable for a few years. What is happening, though, is that the colony is establishing giant seed bank in the soil, waiting for an optimal year when the weather is right and the soil has been disturbed, by say, removing another invasive species or the creating of a new path. Then, the colony suddenly explodes to the point where hand removal becomes an overwhelmingly huge task. People then start to get tempted by plant-killer chemicals which could, of course, kill any surviving desirable plants and potentially cause cancer or other disease in the fauna (including the humans!). Picture: First -year garlic mustard seedlings on the forest floor, Mill River bank near Cloonan, Stamford, CT June 2006 Know the enemy: Remember that garlic mustard is a biannual. The eradication strategy should follow the plant's growth cycle. The first-year basal rosettes can be easily hand pulled, and the removal work can be carried out any time that the ground isn't frozen. Pull gently and tamp the earth back down immediately to minimize soil disturbance. However, no matter how careful you are, pulling the plant up will disturb the earth to some degree and reopen the seed bank, so continued vigilance and, for large areas, over-planting of desired plants is recommended. Over-planting: Where the anti-invasive movement needs to improve is in identifying the best plants for over-planting areas cleared of invasives and getting this information out to the public. One published garlic mustard study showed that jewelweed and box elder seedlings bested the garlic mustard seedlings. Box elder, a native maple, can get a bit weedy itself, so won't be everyone's first choice. Jewelweed, though, has interesting possibilities. It is a native annual that the deer will eat when hungry. It thrives in moist shade, so the seeds are often available in large quantities near areas where we're likely to be pulling out garlic mustard. Someone, please try this and write in about the results. Second-year plants should also be (carefully) pulled up until they start to flower. At this point, the plant can be cut to the ground, instead, thus lessening the soil disturbance (even if a bit hard on the back). If cut all the way to the ground, once in flower, tests show that the plant has a low chance of being able to re-generate. (Caution: if only cut part way to the ground, or cut too early, the plant will come back, possibly with double or triple the flowers.) NOTE: ONCE THE PLANT HAS GONE TO SEED, PULLING UP THE DYING PLANT AND THROWING IT NEXT TO THE TRAIL HELPS IT SPREAD!!!!! Don't do this, tempting as it is. The plant has already reached the end of its life cycle, so pulling it up only disturbs the earth and propels the seeds over a larger area than they could have achieved on their own. Instead, the seeded plant should be cut to the ground as gently as possible so as to keep the seeds intact for bagging. By this stage, it might be the best use of resources to leave the seeded adults alone and concentrate efforts on protecting the earth from disturbance and on the pulling the baby rosettes which will create seeds next year. All roots and all adult plants should be placed in a black plastic bag in the sun to sterilize. (Since this it what it takes to kill the stuff, you can see why garlic mustard is winning). Throwing the roots and seeds in the compost or garbage, or leaving them along the trail, only compounds the problem. picture: New first year garlic mustard in the woods at Scalzi Park, Stamford CT April 2006. The plants will bloom, seed, and die next year. Alternative idea: Since humans are the most effective North American pests for garlic mustard, it has been suggested that we start eating it again. They say it makes an excellent pesto, and it is good for you. Caution: Never eat plants grown near a road or driveway where heavy metals from car exhausts may have poisoned the ground. Also beware of old industrial sites, and dumping sites.

further reading: The Nature Conservancy: Element Stewardship Abstract Public Library of Science: Invasive Plant Suppresses the Growth of Native Tree Seedlings by Disrupting Belowground Mutualisms

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Photo credits: Sue Sweeney � Sue Sweeney 2006

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