One of my new neighbors (from Texas) told me that they had seen white and pink flowers on the ditches and woodland fences. Could it be phlox (Phlox pilosa)? It could have been, but it’s not. These plants are actually dame’s rocket (Hesperis matronalis), a non-native, very invasive member of the mustard family.
This illustration shows the major differences in dame’s rocket and wild blue phlox.
Mustards like dame’s rocket have four petals and alternate leaves, while native phlox have five petals and opposite leaves. Dame’s rocket produces a basal rosette during the first year and flowers the following year.
Imported from Eurasia in 1600s, it thrives in most environments and is a prolific self-seeder and fast-grower. It can enter waterways, quickly overtaking native-plant communities as it successfully competes for light and moisture. Dame’s rocket, like most introduced invasive plants, lacks natural predators and diseases in North America. It appears on forty-six states’ noxious weed lists.
Beware of Wildflower Seed Mixes
Dame’s rocket’s recent spread has been accelerated by its inclusion in “wildflower” seed mixes sold commercially. Beware of nurseries that sell this so-called “wild phlox.” Whenever you can, please help to eradicate non-native invasive species and replace them with native species. We can each do our part to protect the integrity of our local environment.
Janet Allen, of the Wild Ones Habitat Gardening in Central New York chapter, and I know that butterflies use dame’s rocket, but looking at the bigger picture, most information indicates it’s a problem. Here are a few sources:
- USDA Natural Resources Conservation Service “…it spreads rapidly from seed and can be very dense excluding native wildflowers in moist areas of meadows, forest edges, and bottom-land woods.“
- Northwest Michigan – Midwest Invasive Species Information Network “Like most invasive plants, dame’s rocket forms monocultures that replace native plants in high quality natural areas, which in turn reduces critical food resources for birds, butterflies, and other wild creatures. Dame’s rocket is a relative of garlic mustard and often grows with garlic mustard. It has similar growth patterns and can take over habitat of native wildflowers and tree seedlings.”
- Chicago Living Corridors “The plant blooms prolifically and produces large quantities of seed from May into July. Each plant may have several clusters of flowers at various stages of development, enabling the plant to produce both flowers and seeds at the same time.”
- Invasive Organization “Locating and removing plants immediately before seed sets is the best way to prevent the spread of dame’s rocket. Pulling or use of a dandelion digger is most effective when the soil is moist is effective. Flower-heads should be bagged for landfill, or dried and burned where permissible.”
- Matthaei Botanical Gardens and Nichols Arboretum “Dame’s rocket can be removed by pulling out the plant (be sure to remove the taproot). It is best to place in a plastic bag and dispose of in the trash. It should not be composted due to its resilience: underdeveloped seeds of dame’s rocket can still sprout just like its relative, garlic mustard.”
- Applied Ecological Services “Remember, as beautiful as Dame’s rocket may appear, it is an invasive species with the potential to damage entire natural ecosystems. Take action now to defend your environment. For information about various treatment strategies, please contact your state’s Department of Natural Resources.”
Some good native alternatives to dame’s rocket include columbine (Aquilegia canadensis), bee balm, aka bergamot (Monarda fistulosa), any of the phlox (Phlox spp) and harebells (Campanula rotundifolia).
See also dame’s rocket (Hesperis matronalis).