Have you been noticing a 2-3 foot tall wildflower sporting a terminal cluster of conspicuous purple flowers? If so, it is probably Dame’s rocket (Hesperis matronalis). That is not a native plant. It might look pretty, but as they say, looks can be deceiving.
Dame’s rocket is a biennial or short-lived perennial native to Europe. It grows to around 2-3 feet tall and has alternate lance shaped leaves that become smaller upwards on the stem. But what catches our attention is the cluster of four petaled, bright purple flowers, each of which is about three-fourths of an inch in diameter. It should be noted that some plants may produce white or pink flowers, due varietal differences or fading.
At a distance, the casual observer may mistake it for a phlox. But unlike a phlox, which has five petals and is a member of the Phlox Family (Polemoniaceae), Dame’s rocket has four petals and is a member of the mustard family (Brassicaceae). There are maybe a half dozen phlox species native to the North Dakota, but none of them closely resemble Dame’s rocket.
Not only are the flowers of Dame’s rocket colorful, but they also emit a pleasant fragrance, particularly during the evening hours. So, it should come as no surprise that it has been cultivated in Europe as an ornamental since the time of the Roman Empire. It was particularly popular in parts of Europe with the ladies, while a close relative (H. tristis) was popular with the men. It was introduced into North America, as an ornamental, probably in the seventeenth century.
Like many other introduced plants, Dame’s rocket has escaped to become naturalized across much of North America where it may be found on the margins of old farmsteads, open woodlands, roadsides, and other idle or disturbed areas. The spread is partially due to its prolific seed production and also because the seeds are often included in various “wildflower” seed mixtures. It has become an invasive species in several states. States that have designated it as an invasive or noxious weed include Utah, Colorado, Wisconsin, New York, Connecticut, and Massachusetts.
So, as you travel about, be on the lookout for this plant. It looks nice, but may become a problem.
