Q: Dame’s Rocket has been one of my favorite flowers ever since I was a child and fell in love with its perfume.

But now I hear it is invasive. Is it? Should I be ripping it out?

A: The answer is, “It depends,” because the word “invasive” is so loaded. No gardener wants to feel like a criminal, or be one, in the case of plants that have been banned. (The Agriculture Department provides a list at plants.usda.gov/java/noxious

Driver, where Dames Rocket is the spelling used.

Unfortunately, almost everything hardy enough to reproduce without coddling is invasive somewhere. By the standard definition, an invasive species is one that can escape cultivation, that can crowd out other plants and that is not native to the ecosystem in which it is growing.

Dame’s Rocket (Hesperis matronalis), originally from Eurasia, certainly fills that bill. Yet like many other invasive aliens, including dandelions, violets, chickweed, plantain and clover, it has been growing in North America since the Colonists brought it in the 17th century.

And like the Colonists, it has been spreading ever since. It does very well in disturbed ground, so there is more and more suitable habitat.

This brings us to your second question.

Removing the plants, or at least preventing them from setting seed, is wise if you are close to an undisturbed ecosystem that would be harmed by the introduction of H. matronalis.

Otherwise, you might as well concentrate on the dandelions, or on more troublesome invaders like Japanese knotweed, burdock, plantain (plantago species), Japanese barberry, Japanese honeysuckle, garlic mustard and Oriental bittersweet. In many landscapes, these are the sorts of plants likely to move in if you move the Dame’s Rocket out.

Small amount of herbicide works

Q: I want to get rid of an ugly forsythia. If I cut off the canes, can I “paint” the stubs with an herbicide that will prevent it from resprouting? Will this damage future plantings in this area?

A: There are a number of herbicides that work to kill plants when applied to the cut stumps. Most contain either triclopyr or glyphosate. Those containing triclopyr are generally more effective on a broader range of plants. Brush-B-Gon and Vinex are two such herbicides that have directions for treatment of a cut stump. You need just a small amount of herbicide, and its residual effect should last only a week.

Compiled from New York Times and Washington Post reports.