Dame’s Rocket, Sweet Rocket, or Dame’s Violet (Hesperis matronalis) is an attractive, but invasive plant. A common garden flower introduced to America from Europe in colonial times, it is invading Wisconsin woodlands and has the potential to become ecologically devastating to native plant species. This weed in the mustard family has many similarities with garlic mustard, a related plant that has inundated woodlands in southern and eastern Wisconsin in recent years.
Dame’s rocket has been around Wisconsin for many years, but seems to be showing up in more and more sites all the time. It is now at a relatively early stage of encroachment. In Wisconsin it is listed as a “restricted invasive plant.”
This old-fashioned, cottage garden perennial hardy to zone 3 produces rounded flower clusters similar to stock that are very fragrant at night. The plant reaches 3-4 feet tall and has showy flowers that last for several weeks. Dame’s rocket does best in moist, well-drained soil in full sun or partial shade.
It is a short-lived perennial, but a prolific self-seeder that has escaped cultivation and adapted throughout most of the United States. In most areas it is more often seen along roadsides than in gardens. Outside of gardens, it is found along roadsides, woodland edges, and is increasingly moving into good quality forests where it can shade out native wildflowers.
Dame’s rocket is is very noticeable as it is flowering from mid-May to mid-June. The sweet-scented flowers range from white to several shades of pink and purple and grow in terminal racemes (each flower has its own little stalk branching off the main stem). Long, narrow seed pods with many seeds each are produced from each flower spike, with seeds on the lowest pods
maturing before flowering is done. Ground-foraging birds do eat the seeds, but not enough of them to reduce the plants’ population. The plant and flowers are edible, but fairly bitter.
This plant is often confused with taller varieties of phlox, but it can be easily distinguished by counting the petals on the flowers. Dame’s rocket has four petals on each flower, while phlox has five petals. Leaf arrangement is also different on the two plants; Dame’s rocket has lanceolate, toothed leaves that grow alternately along the stems, while phlox has smooth-edged, opposite leaves.
Dame’s rocket is still recommended and sold occasionally by seed companies and nurseries – often listed as deer resistant – and may be found in “wildflower” seed mixes. Because it can spread rapidly, you should think twice about planting it in your garden. Some alternatives to try instead include blue columbine (Aquilegia caerulea), native bee balm (Monarda fistulosa menthaefolia), woodland phlox (Phlox divaricata) or native harebells (Campanula rotundifolia).
As with garlic mustard, the Wisconsin DNR is looking for help from gardeners, hikers and other people who frequent parks and other wild areas to help control the spread of this exotic species. People can help prevent the spread of this invasive plant by pulling Dame’s rocket plants from the ground, being sure to get the roots to prevent resprouting. As seeds remain in the soil for many years, the control work should be repeated each year.
For those gardeners who are reluctant to remove the plants from their yards, spread can be reduced by removing the flower stalk when the flowers begin fading. Remove and destroy all seed pods each year to prevent spread into adjacent areas. Note that composting the plants or flower stalks may not kill the seeds.
– Susan Mahr, University of Wisconsin – Madison
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