It seems that invasive plants have one of two strategies while they quietly try to take over the planet. Either they are so unobtrusive that you’d never notice them until they become a problem (like buckthorn or garlic mustard) or they are so in-your-face gorgeous that you are enthralled by their beauty for years before you notice that they’ve overtaken your world. Dame’s rocket falls into the second category
Dame’s rocket is beautiful. It has two to three foot tall showy white, pink and purple flowers from mid-May through July. Blossoms are ¾” – 1” wide and grow in branching clusters that lengthen over the flowering period. They have a sweet smell that is strongest at night that has been described as a mixture of clove and violet. It’s hard to imagine that something so pretty could be such a troublemaker.
But trouble it is. It forms thick stands that line trail sides, lowland forests, moist meadows, woodland edges and openings, open woods, thickets, semi-shaded fence rows, ditch banks and roadsides. In other words, it grows pretty much everywhere. And those thick colonies of sweetness are competing and winning against native woodland plants that support the birds, insects, and mammals that should be living in the area. Instead of the variety of food and shelter that native plants offer, dame’s rocket provides just one thing – pretty flowers. And birds, insects and mammals don’t really care how attractive their environment is – they need food.
The invasive nature of dame’s rocket kind of snuck up on us, so not a lot of study has been done as to whether the plant changes the chemical composition of the soil in which it grows. But if it’s anything like its close relative, garlic mustard (and it most likely is), it is wreaking havoc on all the soil microbes and other tiny forms of life that make up a healthy soil ecosystem needed to sustain healthy forests.
Dame’s rocket is native to Eurasia, and like so many invasives, is a problem today because of our own stupidity. Or really our ignorance. For many years, seeds of dame’s rocket have been included in wildflower seed mixes. Once planted, it easily escapes cultivation because it spreads by seed and each plant can produce up to 20,000 seeds in long, narrow 5-inch seed pods that develop after flowering. Seeds escape gardens and enter natural areas via rainwater runoff, waterways, vehicle tires, shoes, clothing and animal fur.
Dame’s rocket is a biennial plant, meaning it takes two years to mature. The first year, the plant forms a rosette of lance-shaped green leaves that stays low to the ground. The rosette remains green throughout the first winter. The second spring, a flowering stem with alternating sharply-toothed, pointed leaves emerges.
To control dame’s rocket, first make sure you do not plant a wildflower seed mix containing it. It may be listed by any of the many names listed in the box XXXXX, or by its Latin name, Hesperis matronalis.
The most benign means of controlling established dame’s rocket is to pull the plants in spring when they release easily from moist soil. You will need to be diligent in re-checking the area for several years as there may be seeds buried in the soil from years past that are still viable and it may take that long for the seedbank to be depleted. If plants are in bloom when you pull them, do not compost them, as they will continue to mature and set seed in the compost pile using energy they have stored in their stems and roots, and that will serve to create an even bigger problem.
If pulling the plants is beyond your capabilities or ambition, just whack the flower heads off before they begin to set seed. Look closely, because each plant can have clusters of flowers at various stages of development, enabling the plant to produce both flowers and seeds at the same time. Come back and check a couple weeks later and whack off any new flowerheads that form. Make sure you catch and collect the flowerheads though; they’ll mature and set seed on the ground just as easily as they will on the plant. Burn the flowerheds or bag them and send them to the landfill as allowed under Wisconsin NR40. More on NR40 later.
Prescribed burning in the fall may kill rosettes. If timed right, spring burns will kill newly germinated seedlings and should set back the over-wintered rosettes. However, spring burning may stimulate germination of the seedbank so re-check the area a few weeks after burning. Don’t burn if you aren’t experienced in controlling a prescribed burn. No point in burning down the whole forest or the cabin.
If you feel you must control dame’s rocket with chemical use, you can use glyphosate (Round-up) or tryclopyr. Apply it carefully to foliage on a warm day (over 50⁰) in late fall or early spring when native plants are dormant. Be aware that these chemicals kill all green plants in which they come into contact. They’re not as good, however, at killing tenacious invasives as they are at killing precious garden plants that you accidentally hit with spray, so come back a week or two later and check to make sure you’ve killed all the dame’s rocket and pull or spray the stubborn stragglers.
No matter which control method you choose, follow-up monitoring over several years is necessary.
Wisconsin NR40 (a Department of Natural Resources rule) lists dame’s rocket as a restricted plant, meaning you are not allowed to transport, transfer or introduce the plant, but possession is allowed. This means you may not plant it (check those seed mixes!) but if you already have it on your property, you are not required to remove it. If you care about the environment at all though, you will do so. Don’t try to talk yourself out of controlling it because the rule says you can’t transport it – you are allowed to transport it for disposal.
Trouble by any other name . . .
Dame’s Rocket has many other common names including:
Damask violet
Dame’s violet
Dames-wort
Dame’s gillyflower
Mother-of-the-evening
Night-scented gillyflower
Queen’s gillyflower
Rogue’s gillyflower
Summer lilac
Sweet rocket
Vesper flower
Winter gillyflower
Summary of control measures
- Pull entire plant – burn or bag and send to landfill
- Cut flowerheads before they go to seed – burn or bag and send to landfill
- Controlled burn in spring or fall
- Herbicides – glyphosate or triclopyr
RECHECK AREA IN A COUPLE WEEKS AND ANNUALLY!
Don’t be confused!
Dame’s rocket is often confused with our native wild phlox, which blooms at nearly the same time and whose flowers look very similar. But wild phlox flowers have five petals and dame’s rocket flowers have just four petals each.
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