Dames' rocket (Hesperis matronalis) is a biennial plant of the mustard family that reproduces only by seed. It originated in Europe and was introduced to North America as an ornamental. It is very similar to non-invasive Garden Phlox, which has five petals and opposite leaves, but Dames' rocket has only four petals and bears its leaves alternately.
Stems are erect, several per plant, and grow 50-100cm tall. Upper stems are often branched to increase flowering. First year plants produce only a basal rosette of leaves, with bolting and flowering occurring the second year.
Leaves are alternate, lance-shaped, dark green and hairy on both sides. By the time flowering occurs, basal leaves have withered away.
Flowers and Fruit
Flowers may be white ranging through pink to purple, with four petals. They are borne in loose clusters that bloom by early summer. The flowers are very fragrant, especially in the evening. Seed pods are long and thin, similar to canola pods except they are constricted between seeds.
Dames' rocket requires moderate moisture and thrives in moist woodland soils. It tolerates partial shade such as occurs along forest edges.
This invasive plant will readily choke out competing vegetation, especially on disturbed sites.
Dames' rocket is often a component of wildflower mixes. Never purchase flower mixtures that do not list all species on the label. It may also be known by the common names Dames' Violet or Sweet Rocket.
Hand-pulling is considered the most effective control method, as the shallow root system is easily pulled or dug from moist soils. Plant density may increase after control work due to soil disturbance promoting germination, but repeated removal will exhaust the seed bank and eradicate the infestation.
Consult your local Agricultural Fieldman or Certified Pesticide Dispenser for recommendations.