FACTS FOR FAMILIES: Monarch butterflies, milkweed, and mowing

September 5, 2022 20

Most people that know me know that I am very passionate about protecting monarch butterflies. Their numbers have been rapidly declining each year, primarily due to loss of habitat. So recently when I turned onto the country road leading to my house and saw that the ditches that had been full of milkweed were completely mowed down, I thought it would be appropriate to republish this article from 2018.

I do my best to encourage people to plant milkweed seeds, and I hunt monarch caterpillars and relocate them to my indoor nurseries until they transform and are ready to be released as butterflies. This is the time of year that I see many landowners mowing their ditches, and I cringe to see them mowing down all the milkweed – the only plant that monarch butterflies lay their eggs on and their caterpillars eat. This article was originally written by Extension Horticulture Educator Chris Enroth, and I want to share it again.

Chris says: there is something about mowing that brings a measure of satisfaction to many of us. What is it that we love about mowing? The smell of cut grass? Taming an unruly landscape? To me, it is measurable progress. It seems so often that modern jobs give few tangible results. So much of our work these days is in the digital ether. After a full day’s work, I leave the office by switching off my computer, and all my toiling vanishes with the click of a mouse.

Arriving at home, I seek tasks of visual permanence by working with my hands, cleaning, and of course mowing. This desire to mow often expands beyond the yard as many landowners also mow road banks and ditches.

The constant mowing routine is harming the monarch butterflies

Unfortunately, the constant routine of mowing is harming the monarch butterfly, due to the loss of milkweed. August and September are critical months for the monarch butterfly. This timeframe is when the final generation of the year develops and prepares to make their flight to their overwintering site in Mexico.

I don’t want to burst your mowing bubble, we can all still hop on the zero-turn and get our fix, but there are times when we should avoid mowing areas like ditches, road banks, natural areas, or anywhere that harbors milkweed, the only plant that monarch caterpillars eat.

For those living south of the 40-degree latitude line (including Quincy and on into southern Illinois), mow before April 1 and mow after October 15. If necessary, you can also do a mid-summer mowing from July 1 to July 20.

For those living north of the 40-degree latitude line (including those north of Quincy and up into northern Illinois), mow before May 1 and mow after October 1. A mid-summer mowing can take place from June 30 to July 10.

These dates are based on monarch breeding and migration activities. The mid-summer mowing will still cause some mortality of monarchs.

Other tips for mowing habitat or roadsides:

Don’t mow the entire area. Leave unmown strips to recolonize the cut areas.
Avoid mowing at night when insects are inactive and cannot escape.
Use a minimum cutting height of 8-12 inches. This height removes seed production for many invasive plants while minimizing the impact on native plants.
Use a flushing bar and mow slowly to allow wildlife to escape before the mower passes over.

Milkweed is a disturbance

Milkweed is a disturbance species, and mowing can promote its growth but can be damaging if done during peak times of monarch reproduction and migration.

Following the above-stated mowing guidelines, can help preserve vital monarch habitat. Check out Monarch Joint Venture’s brochure Mowing: Best practices for monarchs https://monarchjointventure.org/images/uploads/documents/MowingForMonarchs.pdf

And it never hurts to plant a few milkweed plants in your garden – they are great for all pollinators!

Cheri Burcham, University of Illinois Extension

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Cheri Burcham is responsible for family life programming in the counties of Coles, Cumberland, Douglas, Moultrie, Shelby and other parts of east central Illinois as needed. Cheri’s emphasis is on healthy lifestyles throughout the life span which include family relationships, communication, caregiving, stress management and human development including early childhood and healthy aging. Her passion is to help people to be their best selves and to promote a healthier, independent older population.