Beware of Invasive Perennials

Nancy Helms, UM Extension Master Gardener in Anoka County, July, 2014

Invasive plants tend to spread prolifically and are often harmful. Any non-native plant that establishes itself and is taking space that should belong to a native species is invasive. None of these plants are native to Minnesota.  



Grecian foxglove is a highly toxic perennial weed. It is poisonous and potentially poisonous to humans and animals, both fresh and dried. The leafy portions of Grecian foxglove could be mistaken for lettuce or other leafy greens and has even been found growing in a homeowner’s vegetable gardens. In its first year, the weed seedling looks like a green rosette with no flowers. Mature plants are two to five feet tall with creamy white, tubular flowers with purplish lines. What sets Grecian foxglove apart from common or garden foxglove is both the flowering stems and undersides of the Grecian foxglove leaves have woolly hairs. Seeds develop in pods with small hooks which attach easily to fur and clothing. Avoid direct contact with this plant as the toxin is absorbed through skin. 

Oriental bittersweet is a deciduous vine that grows up to 66' long. The vines climb by winding around a tree or other support structure. The first confirmed Oriental bittersweet infestations in Minnesota were found, reported, and controlled in 2010. Tracing these infestations back, they were planted along fences by persons who thought they had planted American bittersweet. Oriental bittersweet can be distinguished from American bittersweet by its fruit. Oriental bittersweet has small clusters in the leaf axils, while American Bittersweet has fruit only at the branch tips. Oriental Bittersweet can overrun natural vegetation, strangle shrubs and small trees.

Wild Parsnip is highly invasive and toxic if the plant's sap comes in contact with skin. The sap contains chemicals that are activated by sunlight causing serious burns and blisters. It is a biennial, growing 3 to 5 feet tall with erect, stout, hollow stems and fern-like leaves. It's yellow flowers are in a distinctive upside down umbrella formation, producing seeds. It typically blooms from May to late July. Wild parsnip can be confused with prairie parsley that has flowers and leaves resembling those of wild parsnip. 

Purple Loosestrife is a wetland perennial, 3’-7’ tall, with up to 50 stems topped with lovely purple flower spikes. It has one main leader stem, but many side branches often make the plant look bushy.  It has been ravaging wetland habitats and growing out of control, making it nearly impossible for native plant life to grow. Currently there are about 2,000 purple loosestrife infestations recorded in 77 of Minnesota's 87 counties. While it has been widely planted as an ornamental, don't be tempted to transplant into your own landscape; it is on the prohibited weed list for Minnesota. 

Invasive species damage the lands and waters that native plants and animals need to survive. Controlling or managing invasive plants on your property is a daunting task. Control programs can include manual, mechanical, chemical, biological and cultural components. Be on the lookout and report them to the Minnesota Department of Agriculture.  For more information see: