In past newsletters, invasive plants have been highlighted. But there is a subset of these plants called “noxious weeds.” What is the difference? An invasive plant is any plant that tends to multiply quickly and crowd out other species. There are both native and alien invasive plants. A noxious weed is one of only three plant species named specifically in Wisconsin statutes as requiring control. These are Canada thistle (Cirsium arvense), field bindweed (Convolvulus arvensis) and leafy spurge (Euphorbia esula).
Section 66.0407 states “A person owning, occupying or controlling land shall destroy all noxious weeds on the land,” and “The chairperson of each town . . . may annually on or before May 15 publish a class 2 notice, under chapter 985, that every person is required by law to destroy all noxious weeds, as defined in this section, on lands in the municipality which the person owns, occupies or controls.” The town chairperson also has the right to appoint one or more Weed Commissioners, whose duties are to enforce the statute. A weed commissioner investigates reports of noxious weeds, informs landowners of the requirement to destroy these weeds, or if the landowner does not comply, the weed commissioner causes the weeds to be destroyed. Landowners are billed for the removal on their property taxes.
In addition to noxious weeds, there are two “nuisance weeds” named in Wisconsin statue 23.235: purple loosestrife (Lythrum) and multiflora rose (Rosa multiflora). For these plants “no person may sell, offer for sale, distribute, plant or cultivate any nuisance weed or seeds thereof. Violators are fined up to $100 per offence.
– Christine Molling July, 2009
For more information about invasive plants: http://dnr.wi.gov/topic/Invasives/
Honeysuckle (left) and buckthorn (right). Photo: C. Molling
Two of the more pernicious invasive trees and shrubs in our area are Eurasian honeysuckle and buckthorn. Both of these non-native species crowd out native plants by leafing out early, losing leaves late, and having berries that birds eat, dispersing seeds in their droppings.
Eurasian honeysuckles (several species) are multiple stemmed shrubs with oblong, paired leaflets along somewhat delicate arching branches. They bear white through pink fragrant flowers in spring, and yellow, orange or red ¼” berries in late summer.
Buckthorns (two species) are small to medium shrubs or trees, with dark green oval-elliptical leaves. Buckthorns are easily identified in fall by their shiny black ¼” berries.
Fall is an ideal time to remove these invasives because their showy fruits and their tendency to keep their leaves late make identification easy. Also in fall, the plants draw nutrients back down from their leaves. Cutting them now weakens them. Because both of these shrubs will resprout from their stumps, it is recommended to paint the stumps after cutting with glyphosate (20-25% active ingredient) or triclopyr (12.5% active ingredient). Be sure to use only chemicals approved for over-water use if you are controlling invasives in or near wetlands or surface water. Other control methods can be found at http://dnr.wi.gov/topic/invasives/fact/commonbuckthorn.html for common buckthorn and at http://dnr.wi.gov/topic/invasives/fact/amurhoneysuckle.html for Honeysuckle.
–Christine Molling, WI DNR Sept, 2009
CONTROL THISTLE NOW!
Considered a noxious weed under Wisconsin law, Canada Thistle should not be allowed to go to seed. Following are tips for getting rid of yours.
Mechanical Control: Routine mowing or selective cutting effectively reduces an infestation within 3 or 4 years. Use a scythe or other sharp tool for selective cutting. The ideal time to cut is in the very early bud stage when food reserves are at their lowest point. Plants cut 8 days or more after flowers have opened should be removed from the site because seeds mature quickly. Cutting should be completed prior to flowering and seed set.
For light to moderate infestations, repeated pulling, hand-cutting or mowing with a brush cutter is an option. Plants should be pulled or cut at least three times during the growing season -- for example, in June, August, and September. Some persons have had success killing individual plants by cutting the top and putting table salt down the hollow stem.
Dense infestations of Canada thistle on large sites other than high-quality natural areas can be controlled by mowing close to the ground while the plant is in full bloom or just before flowering. Control will take a few years. If seeds are ripe, cut flower-heads must be removed from the site immediately to avoid further seed dispersal.
Chemical Control: Control of this species with herbicides in natural areas is not recommended, as the herbicide can damage native vegetation more than the damage caused by the thistle. However, spot application of the amine formulation of 2,4-D using a wick applicator or hand sprayer can control individual stems if necessary. For more information see: http://dnr.wi.gov/topic/invasives/fact/canadathistle.html
-Sue Studz July 2006 Newsletter
Photo: C. Molling
Have you seen all those pretty pink flowers blooming along the roadside in June? I always thought they were phlox. I was wrong! These flowers are an alien invader called dame’s rocket (Hesperis matronalis). These Eurasian members of the mustard family are spreading in Wisconsin’s woodlands and fields due to their prolific seed production. They spend their first year as a rosette of leaves and send up a 2-4 ft flower stalk in their 2nd or 3rd year. It’s easy to tell the difference between dame’s rocket and phlox. Dame’s rocket has 4-petaled flowers and alternating toothed leaves, while phlox had 5-petaled flowers and opposite smooth leaves.
To control dame’s rocket, you can cut the flower heads off blooming plants before they set seed, or hand pull the whole plant. As with garlic mustard, don’t leave the pulled plants or try to compost them, as they can still ripen seeds after cutting. Bag the plants or burn immediately. For more information see: http://dnr.wi.gov/topic/invasives/fact/damesrocket.html
UW Extension, Christine Molling June, 2009
WARNING! SAVE THE TOWN FROM INVASION OF GARLIC MUSTARD!
The beauty of the Town of Berry and surrounding areas are being threatened by a European species of plant that is rapidly spreading in Wisconsin.
Now (Spring) is the time to stop it! This plant can consume woodlands in 1-3 years. It shades out the native wildflowers and eventually kills them. Devil’s Lake State Park and the Baraboo Bluffs are covered with it. There are three patches on my land here in the Town of Berry. This is the best time to wipe it out before it gets to the flowering and seed producing stage.
Walk your land and look for large patches of small green plants that are present in early April before most plants are green. Crush a leaf and if it smells like garlic it is garlic mustard Alliaria petiolata.
The plant is a biennial. It will flower the second year. First-year plants appear as a rosette of rounded/kidney shaped green leaves close to the ground. Rosettes remain green through the winter and develop into mature flowering plants the following spring. Flowering plants of garlic mustard reach from 2 to 3-1/2 feet in height and produce buttonlike clusters of small white flowers, each with four petals in the shape of a cross.
My patches are in the first year and I will use a herbicide like Roundup to eliminate them. This may be used in spring or fall. If the stalk elongates and flower buds appear it is best to hand pull and bag them so the seeds do not spread. Prevent any plants from going to seed.
If you do find garlic mustard make sure to look outside the patch for loner plants. I even have one in my flower bed!
Web information may be found at: http://dnr.wi.gov/topic/invasives/fact/garlicmustard.html.
-Mary Bauschelt May 2005 Newsletter
(Lythrum salicaria, L. virgatum, and their hybrids)
Purple Loosestrife displaces native wetland vegetation, degrades wildlife habitat, displaces rare plants and animals, and chokes waterways.
Prevention is the best way to stop purple loosestrife invasion. The following steps are recommended by the Department of Natural Resources (DNR):
- Be on the lookout for pioneering plants or isolated small colonies and remove them immediately.
- Rinse off equipment, boats and trailers, clothing, and footwear used in infested areas before moving into uninfested areas.
- Remove and destroy purple loosestrife planted in lawns and gardens. It is illegal to cultivate purple loosestrife in Wisconsin.
Control methods should be repeated for several years to catch missed plants and those reestablishing from seed.
Small young plants can be hand pulled and be sure to get the entire root or it will resprout. Older plants are generally too big for pulling and are difficult to dig up. Handle plants prior to the onset of seeds (which begins in early August), or cut and bag the seed heads to avoid spreading seeds. Don't throw them in your compost pile.
Mowing has not been found to be an effective way to destroy purple loosestrife unless the plants are cut below a level that water will cover for approximately 12 months.
Careful use of herbicides is the most effective, efficient and least destructive means of removing large purple loosestrife plants. Currently Roundup, for use on dry sites, and Rodeo, for use on wet or standing water sites is the most effective active ingredient for killing loosestrife. It must be applied in late July or August to be most effective.
Garlon 3A has also been recently found to be effective on loosestrife. Its advantage is that it doesn't harm sedges, cattails, rushes, reeds, etc. Garlon 3A currently can be used on dry sites only and is not yet approved for over-water use. A permit is needed from the DNR when applying herbicides to Wisconsin waters. To determine whether you need a permit, contact your local DNR office.
Biological control may be the most viable long-term solution. The DNR, in cooperation with the U.S. Fish and Wildlife Service, is introducing natural insect enemies of purple loosestrife from Europe. Careful research has shown that these insects are dependent on purple loosestrife and are not a threat to other plants.
For more information about purple loosestrife or control methods, contact the Purple Loosestrife Bio-Control Program at Brock.Woods@dnr.state.wi.us or WDNR Research Center at 221-6349 or visit the DNR website at http://dnr.wi.gov/topic/invasives/fact/purpleloosestrife.html
-Submitted by Mary Bauschelt August 2005 Newsletter
Photo courtesy of the Nature Conservancy
Spotted knapweed (Centaurea maculosa) is a shrubby, wiry plant, whose narrow leaves and stems have a grayish blue color. The pink to purple 3/4 inch blooms resemble a soft thistle, with darker tipped comb-like fringes. The plant is often found along roadsides, railroad tracks, and parking lots, but is increasingly found in all sunny natural areas.
Spotted knapweed is best controlled through digging or pulling before it blooms. The whole root must be removed. Mowing is not recommended, as plants respond by flowering at a lower height. Some success has been reported in controlling the plant by using goats to repeatedly graze it down. Spotted knapweed is easily spread by farm machinery or weedy hay, so care should be taken to clean mowing equipment after using in infested areas or when purchasing hay. For more information about spotted knapweed or control methods, visit the DNR website at http://dnr.wi.gov/topic/invasives/fact/spottedknapweed.html
For a complete list of invasive plants including recommended control options, go the Wisconsin Department of Natural Resources web site http://dnr.wi.gov/topic/Invasives/.
A relatively new plant invader to Wisconsin is teasel. Teasel is an aggressive exotic that chokes out native plants.
Common teasel (Dipsacus fullonum subsp. sylvestris) and cut-leaved teasel (Dipsacus laciniatus) were originally introduced from Europe for their pincushion-like seedheads. The seedheads were mounted on frames and stroked against wool cloth to raise the nap, creating a smooth, soft surface. Today, florists use the dried seedheads in decorative displays.
You will recognize teasels by the 2-7 foot dried stalks with spiny, egg-shaped seedheads from the previous year mingled among this year’s green plants. First year plants form a basal rosette of leaves. Older plants form prickly stalks, with paired prickly leaves joined at their bases along the stalk, forming a cup. Do not confuse the native cup-plant with teasel – cup-plant has leaves without prickles and has a relatively smooth stem. Teasels bloom with hundreds of tiny white to lavender florets on each bud.
Teasel is best controlled by pulling the taproot or cutting when buds are formed, but not yet blooming. If already blooming, be sure to dispose of the buds and seedheads by either landfilling or burning, as they can set seed even when cut. Do not attempt to compost. Revisit the area for several years, as seeds can last in the soil. If you receive a floral arrangement containing teasel, do not display it outside. See the WDNR web site listed below for chemical control suggestions.
For a complete list of invasive plants including recommended control options, go the Wisconsin Department of Natural Resources web site http://dnr.wi.gov/topic/invasives/fact/commonteasel.html.
-Christine Molling, WI DNR July, 2008
Wild parsnip (Pastinaca sativa) can be confused with prairie parsley (Polytaenia nuttallii), a native prairie species listed as threatened in Wisconsin. Its flowers and leaves resemble those of wild parsnip. Comparatively, flowers of the prairie parsley plant are light-yellow, sparse, and typically found at the end of the stem. The leaves are pinnately compound like those of the wild parsnip, but are oblong with few teeth.
The plant has a long, thick taproot, which is edible. Flowering plants produce a single, thick stem that contains hundreds of yellow umbellate flowers. The lateral flowers often overtop the terminal flowers. Depending on the habitat and growing conditions, individual flowering plants range to over four feet in height.
If the plant juices come in contact with skin in the presence of sunlight, a rash and/or blistering can occur, as well as skin discoloration that may last several months.
Wild parsnip slowly invades an area in waves following initial infestation. Once the population builds, it spreads rapidly. This species is an aggressive, Eurasian weed that frequently invades and modifies a variety of open habitats.
Controling Wild ParsnipCAUTION: Care should be taken to avoid skin contact with the juices of this plant. Proper clothing (gloves and a long-sleeved shirt) must be worn to prevent the phytophotodermatitic effects.
Mechanical Control: The best way to control wild parsnip is early detection and eradication. A very effective control method is to cut the entire root just below ground level with a sharp shovel or spade. Cutting below ground level prevents resprouting. In some soil types in wet conditions, the plants can be pulled out of the ground by hand. All seeds must be removed from the site and disposed of in a landfill or by burning.
If the population is too large to hand-cut or pull, a power brush-cutter can be used just after peak flowering and before the seeds set. Plants may resprout when cut above the ground, and should be cut again a few weeks later to prevent flowering. Cutting done after seed set will greatly reduce the likelihood that the plants will be able to resprout and flower. Plants cut at this time must all be gathered and removed from the site to prevent mature seed from developing and falling to the ground. Another effective way to eliminate reseeding is to hand-collect all seeds after they have set. If control of flowering or seeding plants is carried out over several years, the population will decrease as the seed bank is depleted.
Burning does not seem to impact the plants themselves--they quickly resprout. However, in the darkened soil following a burn, these rosettes are easy to recognize and can be controlled by hand-digging. Prescribed burning stimulates increased growth in prairie species that may potentially decrease parsnip populations through competition.
Chemical Control: Chemical controls are effective, but should be used sparingly on quality natural areas. The best method is to burn the site, then follow with spot application of 1-3% active ingredient glyphosate.Immediately after a burn, wild parsnip is one of the first plants to green. Glyphosate can be spot applied to the basal rosette of the parsnip with little effect on dormant species.
For more Information on wild parsnip see: http://dnr.wi.gov/topic/invasives/fact/wildparsnip.html
-Mary Bauschelt June 2005 Newsletter