Weed talk: Don’t get merry with Marestail
By Matthew Oehmichen, agronomist
My humble reader, before we begin I must confess that I got a compliment from a reader whose opinion in the matter of writing I take with a lot of significance: my high school English teacher Mrs. Elaine Haas. Certainly, I must have not been viewed as a promising script-master, especially when I couldn’t discern which “there/their” to use in a sentence or apply proper grammar (let alone spell it). With that being said, I am happy to report from one of my former educators that I wasn’t a disappointment after all. I didn’t mean anything boastful from this beginning paragraph other than it is fun to be able to connect with my former teachers once and awhile.
With the spring planting season coming upon us the fields of winter wheat, winter rye, alfalfa, forage grass, and cover crop cocktail mixes are greening up more and more. Recently I was walking my dad’s cover crop fields admiring the thick cover and solid soil beneath my feet until I stumbled on a weed that was greening-up alongside the cover crop. This weed is a rather nuisance to our area farmers: Marestail.
Also known as Canadian Horseweed, it is a native winter annual broadleaf. If we remember back to previous discussions, and annual germinates, produces seed, and dies within a season. What makes it a “winter” annual is it sprouts in the fall, slowly grows under the snow, and takes-off in the spring to produce seed in the summer. Think of it as like a monster hiding under the bed from your childhood; it lies in wait until the right opportunity when you are least suspecting it. By being established with roots in the fall it can pull in enough nutrient reserves to make it through the cold winter, and push ahead of other plants in spring that are just starting to germinate. It starts out like a rosette but then produces a single, hairy stem with multiple bright green elongated leaves from top to bottom of the plant. Most of the time the flowers are white, and look like a “poor-man’s” daisy; a vibrant yellow center adorned with thin white pedals.
Often overlooked, this is the dark horse of difficult weeds in our area. Besides being the first weed in the field it is also very difficult to kill. Tillage can certainly uproot it, but its seeds get buried deeper in the soil profile where it will happily lay in dormancy for many, many years. It is also robust in the spring and able to withstand some herbicides, especially glyphosate (RoundUp). Once it gets 8 to 10 inches tall its ability to store and pull up nutrients is so great, that it can avoid majority of herbicide applications and continue to compete against the crops you are trying to grow. Producing up to 200,000 lightweight seeds equipped with wispy hairs to help it get carried off in the wind, adds to the headache of not only trying to stop this weed, but also trying to contain it.
What makes this plant fascinating is it takes on the attributes of a lot of weeds to make it a force to be reckon with (producing lots of seeds that are easily spread, outcompeting plants by being a winter annual, attractive flower to bring in pollinators, glyphosate resistant), while being a rather boring looking plant (single stem, white flowers). So boring that it hasn’t merit a strong presence on the internet with the “hippies”/medicinal people for its uses. The most common traditional uses I found was that it was a treatment for gut health and “menstrual irregularities”, but it hasn’t been part of a recent study for health benefits for some time.
The best time to take care of this weed is to tackle it in the fall when it is germinating, and to take care of it with a herbicide program that has multiple modes of action. Cover crops can take care of most of the Marestail, but if there is any open space in the field the Marestail will be there. Perennials easily muscle out Marestail, so rotating a multiple year perennial system (like a hayfield) with also knock it out.
