With the start of summer holidays, highway traffic is set to increase as people take road trips to the beach, visit family members and fun places. Those of us who have been commuting all year have already been admiring the beautiful purple, white and lavender coloured flowers along the highway. Sad to report that these flowers, commonly known as Dame's Rocket, are also invasive! Even worse, the first website that came up when I googled this plant to see what came up was how to grow it?! While it is not found on any Michigan invasive species watch list, nor listed on any seed laws by MDARD, they are invasive and are included on the US Forest Service's list of invasive species. Dame's rocket is a biennial plant that is native to Eurasia and belongs to the same family as another common invasive plant, the garlic mustard. During the first year, the plant produces a short rosette with pointy lance shaped leaves that stay green throughout the year. In the following year it can grow up to four feet in height, producing white, purple and/or lavender coloured flowers with four petals. The lag time in flowering is why growth is noticed in bi-yearly waves. They are typically found along highways, roads, woodlands and open areas as they prefer moist areas with proper drainage. With the ability to bloom for most of the summer and high rate of seed production, they can quickly escape gardens and spread to other areas. Due to their popularity, seeds are often harvested and sold in wildflower seed packets (look for the scientific name " Hesperis matronalis") or even as stand alone plants. While very pretty, these flowers are quick to crowd out native plant species, and thus reduce plant biodiversity. They are thought to be allelopathic, meaning they can produce chemicals that prevent other plants from growing around them. If the infestation gets to be large enough, it can impact water drainage, prevent the emergence of tree seedlings, and change what organisms utilize the area. If you have this plant in your yard there are a couple things you can do to manage it. First and foremost, do not plant more of it, and check seed packets for this species. They can be pulled by hand if the infestation is small, but it is important to remove the entire taproot and dispose of the plant in the landfill. When the plant is flowering, you can take a pair of shears or scissors and cut the plant from the flower up (prior to it going to seed). Herbicide may also be used, but should be used according to product's label. Foliar spray using glyphosate or triclopyr can be used, and is more effective when the native plants are dormant and the basal rosettes are green (WDNRb, 2019). For more information, please see the US Forest Service fact sheet (click here). For more information:
USDA. 2019. Weed of the Week: Dame's Rocket. Date Accessed: June 5th, 2019. Website: www.invasive.org/weedcd/pdfs/wow/dames-rocket.pdf WDNR. 2019a. Invasive Species: Dame's rocket (Hesperis matronalis). Date Accessed: June 5th, 2019. Website: https://dnr.wi.gov/topic/invasives/fact/damesrocket.html WDNR. 2019b. Dame's rocket (fact sheet). Date Accessed: June 5th, 2019. Website: http://learningstore.uwex.edu/Assets/pdfs/A3924-06.pdf
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AuthorShikha Singh is the coordinator for the JLW CISMA. She has a BSc. in Biology from University of Western Ontario, and her master's and PhD at Michigan State University from the Dept. of Fisheries and Wildlife. Her areas of expertise include water quality, water policy, invasive species, education/outreach and public speaking. |