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cityofArdenHills.org • J uly 2022 • 5 Purple Loosestrife Purple loosestrife is a wetland plant with showy purple flowers arranged on floral spikes. It is a Prohibited Noxious Weed and an invasive species that can cause recreational, economic, and ecological damage— changing how residents and visitors use and enjoy bodies of water. Problems purple loosestrife can cause include: • Dense growth along shoreland areas that make access to open water difficult • Overtaking the habitat and outcompeting native aquatic plants, potentially lowering plant diversity • Providing unsuitable shelter, food, and nesting habitat for native animals • Changing the hydrology of wetlands through the plant's dense root systems Purple Loosestrife is primarily spread through movement of water equipment and uninformed release of garden plants. The plant produces millions of tiny seeds in shoreland areas. Seeds can be hidden in mud and debris, and stick to boots, waders, and other fishing and hunting gear. Roadside maintenance equipment can also spread this plant and its seeds. The best time to control purple loosestrife is in late June, July, and early August, when it is in flower, plants are easily recognized, and before it goes to seed. Once flower petals start to drop from the bottom of the spike, the plant begins to produce seed. In areas where there are few plants and easy access, manually removing the plants in recommended. It is important to dispose of the plants away from the water. Allow the plants to dry out, then burn if possible. More information about controlling and disposing of Purple Loosestrife can be found dnr.state.mn.us/ invasives/aquaticplants/purpleloosestrife/control.html. Invasive Plant Species in Arden Hills Garlic Mustard Despite its deceptively delicious name, Garlic Mustard is a highly invasive noxious weed prevalent in Arden Hills. Garlic mustard forms thick mats on the forest floor that shade and outcompete native plant species. They impede natural forest regeneration by producing chemicals that reduce growth of other plants in addition to blocking other plants from direct sunlight. Garlic mustard can be spread by transporting mud that contains its tiny seeds, so it is often found along highly-trafficked trails. Hand-pulling individual plants is effective if the entire root is removed. Because flowering garlic mustard can produce seeds even after it's been pulled up by the roots, the Minnesota Department of Agriculture (MDA) recommends that pulled plants be placed in bags for disposal and not simply left on the ground where they were picked. The plants from the bags can be kept on site for burning or piled and covered with a tarp for decay. Herbicide control can be done using a spot application of 2% glyphosate in early spring or late fall when native plants are dormant. This is a systemic herbicide that is taken up by plants and moves within the plant, which can kill leaves, stems, and roots. Carefully and thoroughly clean off boots, clothes and tools before leaving the area to avoid carrying the tiny seeds to new sites. Information for this article was taken from the Minnesota Department of Natural Resources website and the MDA website. Visit cityofardenhills.org/1179/ Other-Invasive-Plants for additional photos of the two invasive plants in this article. Garlic Mustard in bloom mid-season Purple Loostrife in bloom mid-season