Invasive Profile: Dame’s Rocket

By Ally Brown, MNA Intern

One problem with identifying invasive species is that, many times, they appear almost as beautiful as the native species they live among. Garlic mustard (Alliaria petiolata) has been an established invasive in North America for many years, yet without knowing the story behind this species it appears to be just another of Michigan’s many gorgeous flowering plants. This same story follows for another species in the Brassicaceae family which has been spreading throughout Michigan without the same spotlight as garlic mustard.

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Dame’s rocket. Photo: Gary Fewless.

With delicate violet flowers atop a slender green stalk, nothing about this flowering plant seems out of the ordinary for a wildflower native to Michigan; this assumption, however, is sadly misinformed. Dame’s rocket is one of the many common names for Hesperis matronalis, a close relative to the widely known invasive garlic mustard. This relation can be determined visually through examination of the petals and the similarity in shape between the leaves of the two species. An additional similarity Dame’s rocket has to garlic mustard is its two year life cycle –  the first year plant exists as a rosette low to the ground and without flowers, while the second year plant is the more recognizable image shown to the left. An important distinction to make when identifying Dame’s rocket is that it has four petals per flower head. Native phlox species appear similar in structure and flower color yet have five petals per flower head.

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Garlic mustard. Photo: K. Chayka

A plant being nonnative is not enough reason to label it as necessary to remove. For a plant or animal to be labeled as invasive it must present some danger to the health of native species or ecosystems. The abundant seed production and allelopathic nature of Dame’s rocket are a few of the characteristics which qualify it as an invasive species. Similar to other members of the mustard family, a single second year plant can produce dozens of seed pods, each containing many more individual seeds. When released from the confinement of a garden, these seedlings have the potential to overwhelm native plants, thereby altering the composition of native environments. Another characteristic of Dame’s rocket that threatens native species is that it is allelopathic, meaning it has the ability to produce chemicals which stunt the growth of surrounding plants, potentially killing them. With the potential for overwhelming native populations (especially when it is found growing alongside garlic mustard) it is extremely important that Dame’s rocket is reduced in popularity as a yard plant and any that has escaped into surrounding areas is carefully removed.

The process of removing Dame’s rocket can be difficult, as it has a characteristic taproot that extends deep into the soil and makes it hard to pull by hand. One method for effectively removing small stands of this plant is to wait until a light rain has moistened the soil so that careful hand pulling can remove the entirety of the plant and its taproot. The plants should then be placed in a garbage bag that is tightly tied in order to prevent any sort of re-sprouting or further spread. For stands too large for removal of the complete plant, another method of control is to pull the seed pods off the plants and seal those in a plastic bag. This method of invasive species control has been utilized by MNA volunteers and interns at the Dowagiac Woods Nature Sanctuary in southwest Michigan. Removal of garlic mustard seed pods has reduced the spread of invasive plants and protected the variety of wildflowers, lichen, and trees which reside in the area.

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Dowagiac Woods Workday. Photo: Jeremy Emmi

Though each part of nature holds value and beauty, when an organism is brought outside of its natural habitat into a new environment it has the potential to disrupt the equilibrium of those already there. For this reason it is important that invasive species such as Dame’s rocket are discussed and prevented from spreading through stewardship work by organizations like the Michigan Nature Association, as well as sharing knowledge about this and other invasive species to allow the beauty of native ecosystems of Michigan to be conserved.

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The Effects of Invasive Garlic Mustard

By Alyssa Kobylarek, MNA intern

Garlic mustard flowers appear after the second year. Photo via MNA archives.

Garlic mustard flowers appear after the second year. Photo via MNA archives.

At first glance, garlic mustard looks like any other native flower. It has tiny, white flowers that sit atop a bed of green leaves along the forest floor. Passersby may not realize that this plant is one of the worst invaders of forests in the American Northeast and Midwest that was brought to America for food and medicinal uses from Europe and Asia in the 1800s.

Garlic mustard is an invasive herb that has spread throughout much of the United States over the past century. It can be identified as young plants by the garlic odor that is released when the leaves are crushed. The flowers develop on an unbranched stalk and they have four small white petals in a symmetrical arrangement.

Garlic mustard is usually found in undergrowth of disturbed woodlots and forest edges. It spreads fast and easily dominates the undergrowth of some forests, pushing native plants back and reducing diversity among native species. Garlic mustard can form in a dense blanket on the understory. This can kill off native plants that grow there because it controls the light, water and nutrients that are available. Plants most affected by garlic mustard are herbaceous species that grow in similar moist soil in the spring and early summer.

Garlic Mustard at Rizor Nature Sanctuary. Photo by Natalie Kent- Norkowski

Garlic mustard grows in dense clusters and has the potential to cover the forest floor. Photo via MNA archives.

Garlic mustard has been tied to the decrease in native herbaceous species in forested areas. It also releases chemicals that hinder the growth of other plant species and inhibits the growth of grasses and herbs. Other areas of the ecosystem could be affected due to the change in the vegetation. Altering the plant diversity can change leaf litter availability for creatures that survive in them, insects could be affected due to the loss in diversity of egg-laying substrate and plants, and it could prevent tree seedlings from growing.

Deer and other herbivores eat the garlic mustard, but they only remove about two percent of the leaf area. Manual removal of the plant is an effective method for eliminating the species and preventing it from spreading. Many volunteer days at MNA this spring are dedicated to helping remove and prevent garlic mustard in MNA sanctuaries. Take a look at some upcoming dates to get involved and visit www.michigannature.org/events for more dates and information!

  • Wednesday, April 30: Join MNA at the Riley-Shurte Nature Sanctuary (Cass County, near Cassopolis) to help keep the woods free of garlic mustard.
  • Friday, May 2: Help pull garlic mustard in the forest at Lyle and Mary Rizor Nature Sanctuary (Livingston County, near Hartland).
  • Saturday, May 3: Join volunteers to pull garlic mustard in the wooded paradise at Powell Memorial Nature Sanctuary (Lenawee County, near Hudson).
  • Monday, May 5: MNA will host a garlic mustard pull at the popular Dowagiac Woods Nature Sanctuary (Cass County, near Dowagiac).
  • Monday, May 5: Enjoy the beautiful woods, Wolf Creek, and spring wildflowers as we pull garlic mustard at Frances Broehl Memorial No. 1 (Lenawee County, near Onsted).

National Invasive Species Awareness Week: March 3-8

By Katherine Hollins, Regional Stewardship Organizer – Eastern Lower Peninsula

Autumn Olive by Tracy Lee Carroll

Autumn Olive by Tracy Lee Carroll

Stewardship staff and volunteers here at MNA spend a lot of time thinking about, looking at, pulling, chopping, and otherwise dealing with invasive plants. Sometimes it’s hard to imagine what anyone did to keep busy before they arrived!

Since we spend so much time dealing with established populations, it’s easy to forget that the best time to manage invasive plants is when you barely notice their presence. That’s why the Midwest Invasive Species Information Network (MISIN) was established.

Garlic Mustard by eLeSeA

Garlic Mustard by eLeSeA

The MISIN website is host to a great collection of tools and information to help you keep an eye out for invasive plants that may have just arrived in your neighborhood. MISIN has a series of identification tutorials  to help you learn the distinctive features of different invasives, and a free app to let you submit information right from the field.

If the list of tutorials is overwhelming, try starting with some pretty common plants like autumn olive, phragmites, or garlic mustard. See if you can find them along the road or in your neighborhood. Once you’re familiar with those, move on to some less-common, but on-the-move invasives like black swallowwort. MNA staff and seasoned volunteers are always happy to help you learn new invasives at our regularly scheduled volunteer days.

Volunteers at a Dauner Martin Nature Sanctuary workday

Volunteers at a Dauner Martin Nature Sanctuary workday

What’s even better than early detection? Prevention! Check out this short video about preventing aquatic hitchhikers, or if you’re eager to cozy up on a long winter night, the US Department of the Interior put together a hefty guide to cleaning equipment and vehicles to prevent the transport of invasives. And if you’re planning some new landscaping at your house, you can use this app or pdf to identify alternatives to invasive plants.

There are also many national events going on during National Invasive Species Awareness Week. For a complete list, visit the NISAW website. The first step is raising awareness, so don’t forget to share what you learn with your friends and neighbors!