Wednesday, June 5, 2013

Dame's Rocket

Dame’s Rocket (Hesperis matronalis) is another invasive alien, albeit an attractive one, in the mustard family. It is now widespread along roadsides, woods edges and damp thickets, but it started as a garden escape after it was introduced from Eurasia. (There's a range map on the USDA Plants Database.) Many years ago, we tried growing it on our dry hilltop, but it never took hold (probably a good thing in retro-spect), so look for it in lower areas with partial shade. It seems to prefer moist soil but avoids true wetlands.  As an example, at the Montezuma Audubon Center, it grows throughout the walnut grove and around the edges, but it’s generally absent from the open fields.

Also known as Purple Rocket, this biennial or short-lived perennial herb comes in a range of colors from pale lavender to hot pink and purple. All of the blossoms on an individual plant are usually the same color, but adjacent plants may vary widely. Light and dark colors are often mixed together in the same vicinity and sometimes you’ll find flowers with white streaks on purple petals. Rarely, several colors are mixed on the same flower. The four petals make an “X” or cross, which is characteristic of the mustards (the Brassicaceae, formerly Cruciferae). At first glance it resembles Phlox, but Phlox has five petals (the same as the number of letters in its name).

Dame's Rocket in front of Yellow Rocket (Common Winter Cress, Barbarea vulgaris)

The purple variety of Dame’s Rocket generally produces more seeds per plant and seems to be the dominant color. The stalked seed pods are thin and erect and split open when ripe. The plant usually grows several feet tall. The lance-shaped leaves are long-pointed, toothed along the margins and they alternate (i.e., are not opposite) along the hairy main stem below the flower and seed clusters.

more of the complete Dame's Rocket plant showing some of the leaves

The best time to enjoy this plant may be when it’s backlit by the afternoon sun. In the evening it gives off a lovely fragrance, probably timed to specific pollinators that rest during the day. This is reflected in another common name for the plant, the night-scented gilliflower. The scientific genus name, Hesperis, is Greek for evening.

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