Dame's Rocket is an introduced, erect 2 - 5 foot tall biennial, found primarily in the woodland areas. Stems are green with fine hair, usually with little branching at the base but with branching at the top. A basal rosette forms the first year with the flowering stem rising the second year.
Leaves are ovate/lance shaped, toothed and alternate, the upper leaves touch but do not clasp the stem. Lower leaves are longer with a stalk (comparison photo below). Stem and leaves have fine soft hair.
The inflorescence is a loose cluster of stalked flowers, terminal and in smaller clusters from the upper leaf axils.
The fragrant flowers (fragrance mostly noticeable in the evening) are 4-part, tubular with the petals spreading to about one inch wide. Color can vary from white to pink. The calyx tube of the flower is about one inch long, with four linear pointed sepals that have dark green tips - the calyx with fine hair. The four petals are widest toward the tip, slightly ragged edges, an indentation at the tip with a distinct point rising from the bottom of the indentation. Petal bases narrow at the calyx tube. The stamens and pistil are visible only at the mouth of the corolla. Stamens number six and are in 3 sets of pairs with an outer pair shorter than the two inner pairs. The shorter ones each have a nectar gland at their base.
Seed: Dame's Rocket can have a prolonged bloom period, and like most Mustard Family flowers, they open from the bottom of the spike upward, while the long, thin seed pods form below from the decaying lower flowers. Each seed pod ascends slightly from the old flower stalk. Pods (called 'siliques') are long and thin and contain a number of oblong flattened seeds that are dispelled when the pod splits into 2 sections along its longitudinal axis.
Invasive: The plant is an escapee from gardens and is quite a spreader, becoming invasive when control measures are not taken. It is a prohibited plant in several states. Like most plants that become invasive, it grows fast and blooms and seeds early before the less vigorous native plants can take hold. It is, however, very pretty and fragrant.
Habitat: Dame's Rocket grows best in moist soils in partial sun. It has a taproot and secondary fibrous roots and propagates from seed.
Names: The "Rocket" part of the name, according to Mrs. Grieve, (Ref. 7) comes from the language of flowers and "Rocket has been taken to represent deceit since the plant gives off a lovely perfume in the evening, but in the daytime has none." "Rocket" is part of the common name of many plants of Mustard Family. The genus name, Hesperis, is Greek for "evening" or "Vesper-flower", as that is when the fragrance is greatest, and matronalis is Latin and alludes to the March 1st Roman festival of Matrons, and indicates the flower was a favorite of married women - hence altogether - Dame's Rocket. The author name for the plant classification from 1753 - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: In size and color Dame's Rocket may resemble some of the phlox family plants - but they have 5 petals. In a closer comparison is Fireweed, Epilobium angustifolium, where the flowers are also 4-petaled, magenta in color, the plant is just as tall, but the leaves are linear without the coarse teeth.
The flowers can vary in color depending on the soil and amount of sun received. Some can also be white as shown in the photos below.
Below: 2nd photo - A new rosette has formed in the fall near the base of the past season's flower stalk.
Below: A grouping of white flowered plants close to five feet high. Note the number of axillary flower clusters.
Below: 1st photo - Each flower produces a long thin seed pod, a silique, which (2nd photo) is attached to the flower stalk and held outward in an ascending position.
Below: 1st photo - Pods contain a number of oblong flattened seeds that are dispelled when the pod splits into 2 sections along its longitudinal axis. 2nd photo - The upper leaves touch but do not clasp the stem
Below: 1st photo - The flower calyx has 4 long pointed lobes with dark green tips - all covered with hair. 2nd photo - Stems have fine hair as does the leaf surface. 3rd photo - comparison of the upper stem leaf on the left and the longer, stalked lower stem leaf.
Below: An extensive growth of Dame's Rocket in the marsh area of the Woodland Garden.
Notes: Dame's Rocket is not indigenous to the Garden area. Eloise Butler noted planting it on June 16, 1915 with plants she sourced from the 'Big Bog' at Lake Minnetonka (west of Minneapolis). More were planted in 1927 and 1929. It was listed on Martha Crone's 1951 inventory of plants in the Garden at that time. She noted planting both pink and white types in 1947 and pinks in 1951. It has naturalized in North American throughout most of Canada and all of the United States except the states of the Gulf Coast and Arizona. In Minnesota, escaped populations will be found in those counties that have cities of size, particularly the metro area counties. It is the only species of Hesperis found in Minnesota or in North America, although there are 25 species world-wide. In an early spring like 2010 and 2012 first flowers can appear before May 1st and flowering can continue well into the summer.
Lore and Use: This flower was especially popular in Europe, having originated in Italy, and thus was brought over to North America. It was a favorite of Marie Antoinette. There is some early medicinal lore of using the plant as a diuretic and an expectorant and for inducing sweating. Gerard (Ref. #6a) and Culpepper (Ref. #4a) are said to have mentioned it.
Monet grew Dame's Rocket in his garden at Giverny to contrast with his irises that dominate the garden in May. Today it is regularly planted there in late March to be in flower for the May Irises. After May it is dead-headed and the foliage is kept for the summer annuals to grow through. (Ref.# 36a)
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"