Invasive Plants, Pacific Northwest
Dame’s rocket is a showy, short lived perennial with large, loose clusters of fragrant white, pink or purple flowers that bloom from May to August on flowering stalks up to 1 meter in height.
This is an invasive plant but very pretty. It grows profusely on Vancouver Island. This plant usually grows in moist woodlands, on woodland edges, along roadsides, and also in open areas.
This member of the mustard family has flowers with four petals. Many seeds are produced in long, narrow fruits. The leaves are oblong, sharply toothed, and alternately arranged. Leaves decrease in size as they ascend the stem. The over wintering rosette is easily identified from fall through spring. This species is often confused with garden phlox. Unlike dame’s rocket, the phlox species have opposite leaves that are not toothed, and flowers with five petals, not four.
Dame’s rocket is planted as an ornamental, but quickly escapes cultivation because of its prolific seed set. Unfortunately, part of its success can be attributed to its wide distribution in wildflower seed mixes. It generally produces a basal rosette the first year, flowering the following year. The plants are prolific bloomers and produce large quantities of seed from May into July. Each plant may have several clusters of flowers at various stages of development, enabling the plant to produce both flowers and seeds at the same time.
Dame’s rocket has not been studied extensively. In fact, it is not yet widely recognized as an invasive plant. Consequently, this plant may not be recognized as a troublesome species until it is well established and then we could have a major problem.
Locating and removing plants immediately before seed sets is the best way to prevent the spread of dame’s rocket.
Be sure to check the contents of “wildflower” seed mixes for this species, and do not plant those that carry it.
Plants in urban gardens may not pose a problem, but any plant whose seed may escape to roadsides or woodlots should be eradicated or prevented from going to seed by cutting the flower heads after they bloom. Pulling may need to be done for several years to remove new plants established from older seed.