If “yellow rocket” refers to the the swift, spring-time explosion of mustard yellow flowers in local fields and ditches, then this is a very appropriate name for a wildflower. Yellow Rocket, or Common Winter Cress, blooms in profusion from April to June in Southwest Virginia.
Yellow rocket is in the mustard family (Brassicaceae), a group that contains plants that have 4-petaled flowers that roughly form an “x”. Even though all the mustards have a similar flower arrangement, they are not all yellow in color–think about garlic mustard (white) or cutleaf toothwort (pink to white) or dame’s rocket (pink, purple or white)–as examples. But among the yellow-flowered mustards, there can be great confusion, because so many of those species look alike.
How do I know if this is field mustard or winter cress? Although the flowers are similar in both species, the morphology of the basal leaves and stem leaves can be quite distinctive. According to the Peterson Field Guide, the stem leaves of yellow rocket are “broad, toothed, and clasping”*, and they get smaller as you go up the stem, as seen in the photos below. Field mustard has a very different leaf–which I’ll report on soon. Meanwhile, this one is Burbarea vulgaris.
Winter cress grows 2-3 ft. in height; it is smooth and dark green, and looks quite succulent. (Some say the leaves are edible when young). It is an introduced species, but it can now be found growing in fields and along roadsides throughout North America.Below is a detailed drawing of the parts of Burbarea vulgaris, or yellow rocket. Compare it closely with the photos.
For the photos, click to open a larger viewer.
Illustration on this page: Barbarea vulgaris R.Br., Atlas des lantes de France. 1891.