The plentiful fragrant flowers are produced in large showy terminal racemes, that can be 30+cm tall, that elongate as the flowers of the inflorescence bloom. When stems have both flowers and fruits, the weight sometimes causes the stems to bend. Each flower is large (2 cm across), with four petals. Flower coloration varies, with different shades of lavender and purple most common, but white, pink, and even some flowers with mixed colors exist in cultivated forms. A few different double-flowered varieties also exist. The four Petals are clawed and hairless. The flowers have six stamens in two groups, the 4 closest to the ovary are longer than the two oppositely positioned. Stigmas are two-lobed. The four sepals are erect and form a mock tube around the claws of the petals and are also colored similarly to the petals.
Some plants may bloom until August, but warm weather greatly shortens the duration on each flowers blooming. Seeds are produced in thin fruits that are 5–14 cm long pods, containing two rows of seeds separated by a dimple. The fruits are terete and open by way of glabrous valves, constricted between the seeds like a pea-pod. Seeds are oblong shaped and 3-4 mm long and 1-1.5 mm wide.
In North America Hesperis matronalis is often confused with native Phlox species that also have similar large showy flower clusters. They can be distinguished from each other by foliage and flower differences; Dame's rocket has alternately arranged leaves and four petals per flower, while phlox have opposite leaves and five petals.
The successful spread of Dame's Rocket in North America is attributed to its prolific seed production and because the seeds are often included in prepackaged "wildflower seed" mixes that are sold for "naturalizing". The plants typically produce a low-lying rosette of foliage the first year, in subsequent years, blooming and seed production occurs in tandem throughout the blooming season. This species is commonly found in roadside ditches, dumps and in open woodland settings, were it is noticed when in bloom. It makes an attractive, hardy garden plant and probably does not pose a threat in urban settings.
Hesperis matronalis is propagated by seeds, but desirable individuals including the double flowering forms are propagated from cuttings or division of the clumps.
Dame's Rocket was brought to North America in the 17th century and has since become naturalized there.
In Europe, Dame's Rocket is host to the caterpillars of several butterfly species, including the Orange tip (Anthocharis cardamines) and Cabbage White (Pieris rapae); and moths such as Plutella porrectella.