Michler & Brown, LLC

The following are some examples of the major weeds we face and the battles we wage against them.  Most of the information here is anecdotal but can be trusted do to our vast experience and suffering brought about by years of trial and error.  The Wisconsin DNR has compiled a more exhaustive list of invasive species, including  those that are classified as prohibited.

Different weeds, and plants in general, have different life cycles.  The three main main ones are perennial, biennial and annual.

Perennial plants are usually long lived and flower year after year from the same individual.  This category includes the obvious like brush and trees, but also countless wildflowers (natives and exotics) that grow new plant bodies every year from a permanent root stalk. 

Biennial  is a category that includes many of the worst weeds we face, and it's possible that this life cycle contributes to why they are so difficult to control.  These include old favorites like Garlic Mustard (Alliaria petiolata), the Sweet Clovers (Melilotus alba and officinalis), Burdock (Arctium minus) and some some newbies like Hedge Parsley (Torilis japonica).  A spring biennial starts its sporophyte (main plant body) life as a cotyledon (as do perennials and annuals).  As the summer and fall seasons unfold, the survivors change to a rosette stage that remains green over winter.  The following spring, the rosette bolts into an adult flowering stage that sets seed for the following season. 

Annual plants grow from cotyledons to adult flowering stage all in the same season.

Garlic mustard (Alliaria petiolata)-Due to its ubiquity and density, garlic mustard warrented a haiku-

Garlic mustard sends

legions of cotyledons

causing a lesion*

 * C. Knief

It's difficult to know where to start with garlic mustard.  It's a member of the brassicaceae family which is still called crucifereae (because the flowers have four petals) by the traditionalists. Most people have at least heard of garlic mustard, and know that it's a problem in Wisconsin's woods.  When coming up with strategies for dealing with this biennial (pulling and spraying in the spring and fall are most common), one should begin by determining how much manpower is available.  For a lot of groups, pulling is the preferred method of removal, and hence, the proliferation of countless garlic mustard pulling parties throughout the state in the spring.  This is fine if you've got enough dedicated people (the best attempt at controlling huge infestations with pulling probably occurs at the Lakeshore Nature Preserve at UW Madison).  But many areas are large, and covered so solidly that a veritable army would be required to pull it before seed set in June/July.  Also, if too many people are tramping through the woods and disturbing the soil by pulling up plants, that in itself becomes an impact on the environment. Another advantage to pulling is to use part of the plant to make pesto!

Some people have had success burning the plant with a propane torch.  We have not had any experience with it, in part since you need a damp/drizzly day and if one has  numerous jobs sites we can't rely on such weather to make it feasible. 

The fastest way to deal with garlic mustard is to spray it with herbicide, usually with a back pack sprayer and sometimes even with a hose attached to a pumper unit if it's so thick that it's a virtual monoculture.  The drawback with herbicides is that there are varying degrees of toxicity to the environment depending on which ones are used.  For garlic mustard, we primarily use Round-Up, Garlon 3-A, 2-4 D, or Escort, all of which have relatively low residual effects on the environment. 

Whether pulling, spraying or burning, it will take many years to get a bad infestation of garlic mustard (and most other weeds for that matter) under control because the seed bank for garlic mustard can last at least 7 years.  That's why we go after the first year plants (cotyledons in spring and rosettes in fall) if time permits.

Wild Parsnip (Pastinaca sativa) is an immigrant from Europe brought over for its food value, and a member of the carrot family (Apiaceae).  The root of the first year plant is delicious when fried in butter, as are most things.  Parsnip is classified as a monocarpic perennial, which means that the rosette may exist for more than one season before it bolts into the mature seeding body.  This plant has taken over roadsides and gained a foothold in many a besieged prairie.  We mainly mow and pull this species, though mowing has to be done twice, or if cut once, must be timed perfectly or it will just re-sprout and flower again.  For southern WI the consensus is to cut near July 4.  We have recently heard of people cutting and treating the cut stems with a 2% solution of Round-Up (41% glyphosate active ingredient) in water.

photo by Chris Evans

Parsnip is perhaps most famous for its caustic effect (phytophotodermatitis) on human skin.  After contact on bare skin, painful blisters will form after exposure to sunlight.  The pain is worse if the blisters are popped which should serve as a warning to those who can't help themselves.  It also seems that every year, some weed warriors insist that it's not that bad and have to learn all over again as they carry their burn marks for the rest of the summer.  It doesn't help that it is usually very hot when parsnip is mowed or pulled, and a person with a brush cutter doesn't last long in long sleeves and a hood.  Because of this, the neck and forearms are the most commonly afflicted areas.  If you are careful, you can pull it without too much exposure.  We also think sunscreen helps to protect the skin by stopping the UV rays of the sun.

Some people swear by the "parsnip predator," which is basically a small shovel with a modified tip that is designed to cut the root a few inches under the soil surface.  This requires minimal contact because you don't have to grab the plant.  Some prefer to grab it (with gloves) as the shovel loosens the root and pull out the whole plant to make sure.         

White and Yellow Sweet Clover (Melilotus alba and M. officinalis) are very similar species and take over in the same way parsnip does.  Yellow sweet clover blooms a little earlier than white.

These plants of the fabaceae family (legumineae for you old timers) are biennials and can be seen on the sides of roads and, unfortunately, in most prairies.  Brush cutting/mowing sweet clover at the proper time is easier than parsnip mainly because you don't have to worry about getting burns from flying plant matter.   As cutters become more skilled they can minimize the throwback and still cut quickly and efficiently.  Often (owing to the rotation of the blade) cutting from right to left offers more control, but one needs to be careful not to pull up as they do it or they'll get a face full.  These same rules apply when cutting brush as well.  In any case, timing for mowing is crucial for sweet clover as well.  Some folks look for the base of the stem to turn red, others look for the beginning of seed formation as the time to cut.

Pulling this plant is often done as long as you get the entire root, though the big ones require a shovel (the parsnip predator works well).  Again, the effectiveness of this method depends on the level of infestation and the number of bodies you have.  Areas with wet, loose soil are easier to pull effectilvely.  Spraying (with Transline and Milestone, among others) can be done for bad infestations, though great care must be taken to avoid collateral damage.   

Reed canary grass (Phalaris arundinacae)  Reed canary grass is an aggressive plant that infests wetlands in particular.  Much work has been done in trying to control it, making it an area of active research.  Reed canary grass sets seed early in the year, about the same time as garlic mustard.  Currently we use a grass specific herbicide such as Intensity in dry areas and a general herbicide approved for aquatic conditions, such as Habitat, for stream banks and wet areas.  Hand pulling is not a viable option although some areas have been bulldozed successfully.  So far we have observed that even with successful spraying, it takes several years to get the infestation under control.

Phragmites (Phragmites australis)  This invasive grass grows to heights of 10 feet or more and can form thick monotypic stands.  It is generally found along shorelines and in wetlands.  We use Habitat to control this plant.  Plant populations decrease dramatically even after one successful application.  Due to the fact that it sets seed late in the season, we are able to spray phragmites in August, as long as the plant stem is still green.  For small infestations and lots of manpower, people bundle the stems with twine, cut the stems and spray the cut stems with a solution of 20% glyphosate.  This technique works well in areas with many desirable plants growing within the infestation.

Spotted Knapweed (Centaurea biebersteinii, c. stoebe)  This member of the asteraceae (compositeae) family is found in dry areas and is one the most loathsome plants we encounter.  Not only is it an aggressive perennial with stems so slender that treating it with roundup is ineffective without nuking an entire area, but it is shunned by potential grazers, and is allelopathic; (i.e. a chemical secretion from the plant creates a localized dead zone which can result in a virtual desert).   

Trees and Shrubs

By far the two most notorious examples of this group are Asian Honeysuckle (Lonicera spp.)and Common Buckthorn (Rhamnus cathartica).  Both create a canopy in the understory of forests, shading out wildflowers and native shrubs and reducing the diversity of ecosystems.  These two species are so ubiquitous, they can be seen in the woods from one's car on almost any country road.  Honeysuckle blooms and leafs out early, so its effect on the understory is clearly illustrated in the spring.  Buckthorn holds on to its leaves later than most trees, so its presence in the understory is most visible in  late fall.  Honeysuckle is a shrub whose champions can take up the space of a large room, and reach a height over ten feet.  Buckthorn is a small convoluted tree that reaches heights up to 20 feet.  Cutting large members of these two species by hand is a project. In a strange way, they're like math problems that must be simplified before you can solve them.  They have to be whittled down to manageable pieces before you can finally finish them off.  In either case, the cut stems must be treated chemically or the effort is wasted,

Buckthorn leaf and berries- photo by S. Garske    Honeysuckle bush- photo by E.Sutton

It's safe to say that most of our brush clearing concerns these two culprits.  We usually use the "cut and treat" method of removal- that is, we cut the individual shub, and treat the resulting stump with specific concentrations of herbicide, depending their uses and effectiveness.  As far as the mess is concerned, there are various ways to deal with that.  Our preferred method is to burn the brush as we go (when there is snow cover), or make piles for future burning.  This serves the dual purpose of quickly clearing the area, and keeping us warm during the colder months.  Building a good brush pile is a process we have perfected to embarrassing lengths, but it's worth it because a badly built brush pile will burn badly, or not at all.  This is also true of the act of tossing brush onto a burning pile.  Helter skelter and/or lazy tossing will quickly turn a pile into a tall, massive,  unburned thicket with a hollow core where there used to be fire.

Other methods of dealing with trees and brush include girdling the trunks (usually with herbicide but also by hand) and leaving the clearing for later when the dead plants start to fall down. 

Clearing is also done with large equipment like an ASV (though not by us).  This method also leaves work for later, usually in the form of re-sprouts and a horrible mess that must be treated and cleaned up by hand anyway.  It looks great initially from a distance.