Mowing milkweed means more monarchs

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A monarch butterfly. Image: Pixabay user skeeze, 2019

By Kelsi Kroll

The monarch butterfly might be on the decline, but a little milkweed-whacking can help get them back on their feet, experts say.

Monarch butterflies are choosy, said Nathan Haan, a post-doctoral research associate at Michigan State University’s Landis Lab, an entomology research center. They lay their eggs exclusively on milkweeds, a group of flowering plants known for bleeding chalky latex from their damaged leaves and stems. The butterflies strongly prefer fresh, young milkweed plants to older ones, Haan said.

And that’s where the weed-whacking comes into play. Chopping down milkweed stems won’t kill them – the plants have an underground network of buds, so stems pop right back up just as soon as they’re sliced down. By mowing plots of milkweed plants midway through last summer, the researchers created a golden opportunity for the monarch butterfly: a slew of freshly-regenerated milkweeds, temporarily free of predators, which are killed in the mowing.

“I was surprised by the strong and relatively long-lasting effect of mowing in reducing predator communities,” said Doug Landis, a Michigan State University distinguished professor and the leader of the lab. “I think it’s possible that strategically-timed mowing can be used to enhance monarch habitat across the breeding region.”

The controlled destruction of a habitat to preserve its species might seem paradoxical, but it’s not, Haan said. In fact, the monarch is just one of many species that depend on a cycle of habitat death and regeneration to flourish. One prominent example is the Kirtland’s warbler, a yellow-bellied songbird that makes its home in young jack pines, a tree that relies on death by fire to reproduce. The flames’ heat opens the jack pine’s otherwise resin-sealed seed cones, ensuring a new generation of trees suitable for the warbler, according to the National Audubon Society.

Researching insects is hard work. Click play above to hear 2018 summer research technicians Lane Proctor, Lindsie Egedy and Kelsi Kroll talk about what it’s like to be a field technician carrying out the entomology research experiments that yielded hopeful news for the monarch butterfly.

“It’s counter-intuitive because sometimes their habitat is destroyed on the short-term in order to be maintained in the long-term,” Haan said. “But there are lots of examples of disturbance-dependent butterflies that use host plants in grasslands or wetlands.”

The study’s results indicate that some mild, midsummer milkweed mowing (say that three times fast) could bolster the butterfly’s numbers. And it’s not just scientists who can lend the monarch a helping hand – anyone with a garden and a weed whacker can aid in its recovery.

“Gardens present an ideal opportunity,” Landis said. “I suggest that gardeners consider cutting back some stems of common milkweed at flowering time and see if they subsequently see more monarch eggs and larvae.”

The lab’s findings couldn’t come any sooner. Monarch populations are plummeting, according to a 2018 study by The Xerces Society for Invertebrate Conservation. Eastern populations have declined by 14.8%, and Western populations have declined by an alarming 86%, according to the study.

“It can be hard to wrap one’s mind around the scope of this decline,” the study says. “The decline from 4.5 million to 28,429 monarchs is similar to the difference in size between Los Angeles and Monterey.”

But the horizon isn’t all doom and gloom for the illustrious butterfly. The monarch is a hardy species, Landis said.

“Their populations are remarkably resilient and capable of tripling their numbers from year to year,” he said. “I think that, with our help, the monarch can recover to stable population levels.”

Haan is optimistic, too.

“Monarchs are an iconic species. They’re lots of peoples’ favorite insect, and they have a unique migratory pattern that spans thousands of miles,” he said.

“People are excited about monarchs, so I think there is motivation to conserve them.”

Great Lakes Echo reporter Kelsi Kroll worked as a field technician for Michigan State University’s Landis Lab in the summer of 2018.

17 thoughts on “Mowing milkweed means more monarchs

  1. I have the Butterfly Weed in my butterfly garden. Would this work the same way?

  2. “Gardens present an ideal opportunity,” Landis said. “I suggest that gardeners consider cutting back some stems of common milkweed at flowering time and see if they subsequently see more monarch eggs and larvae.”. I’d hate to cut them, not only do they smell nice, I have found some eggs on them

  3. Do they mean cut back to the ground or cut back as in prune??? I can’t mow mine because it’s in a butterfly garden, interspersed with many other plants, but I’d still like to know if they mean mow down to ground or weed whack 2/3 off, etc?

  4. I also have found that Monarch like to lay their eggs on the youngest of milkweed plants, even though that plant wouldn’t be enough to feed the caterpillar through even 2 or 3 instars. Larger milkweed plants, when clipped, seem to throw all their energy into a new shoot or shoots near the cut so fast it really is amazing. I don’t mow my milkweed, I just clip off the top 6 or 8 inches and use that clipped off part to feed Monarch caterpillars that I raise. Stick the stem in water and that clipping will firm up and the caterpillars will dine on it readily. No more than 1 or 2 caterpillars per clipping to minimize disease.

  5. I ordered a pack of seeds and had 2 to sprout. I found some common milkweed by the road and dug up one small plant. Trying to get some established on my property. Good article.

  6. this didn’t help me at all – I don’t want to mow and KILL eggs or catepillars so when the hell do I mow when I know I won’t be killing a monarch ?

  7. For anyone trying to establish a planting bed use the seed ball method. The clay protects the seed from birds and mice. Plant in the fall for the needed cold stratification process. see instructions at Happy Planting!

  8. We’ve found this to be very true. The Monarchs will leave eggs on young fresh milkweed vs the older plants. We mow half of the field at a time so that there are blossoms on the old weed for nectar and and new milkweed in the mowed section where the Monarchs prefer to lay their eggs.

  9. WHEN TO CUT? I have twice the milkweed plants as last year and did nothing. I live in northern Michigan and am open to cutting back the plants. But when? When flower is fully blooming? Early bloom? Article is not clear to me. I have already seen monarch caterpillers on the plants. Photo would help!


    This article in the Free Press recommends cutting one-third of your Milkweed stalks in June and July. Common Milkweed has the most fragrant and beautiful flower, so I will wait until after they bloom to cut. I will let a few stalks mature to produce seedpods. I wait until the black-and-orange bugs try to open the pods before I collect the pods in late fall. Then I harvest the pods to plant in a nearby urban meadow we have been trying to establish in an abandoned park area. It is best not to plant Milkweed near roads or streets to avoid butterfly-car collisions.

  11. I raise milk weed and to get common milkweed to germinate you need cold stratified seeds a heating pad and wet paper towels laid in a lidded plastic container with a couple of holes in the lid. Put paper towels in container and wet paper towels with water. Place seeds on wet paper towels and then put on the lid. Place container on seed germination heating pad. Within 3 or 4 days the seeds will start to pop out a white root. Spritz seeds a couple of times a day with spray bottle of water. When seeds get leaves then plant the germinated milkweed in soil and make sure you have good humidity to keep the seedling from dying. I put a clear baggy over the small pot to keep the humidity high and put by window so it grows. Eventually remove the baggy after a week or two. It is a learning experience and you will get better if you pay attention. Eventually I plant about 4 plants per 5 gallon bucket that I drill plenty of holes in the bottom for drainage. After monarch season ends I then plant the milkweed in the ground and the following year they come up like crazy. Good luck.

  12. Visit to learn about growing milkweed from seed. Or YouTube has video lessons. There is a method with cold temperatures and wet paper towels.

  13. It seems that timing could be key – how does one know when mowing will do more good than harm, or determine the appropriate date range for mid-summer mowing?

  14. For some reason I can not grow the common milkweed we ordered live ones with pink flowers. Those grow but I even planted the seeds in potting soil with not growth

  15. I am redoing some space in my garden in Rockford. IL
    I would like advce on which plant are best for hummingbirds, butter flies and birds in my area.

  16. Thanks for your efforts to save the Monarch. I’ll try the weed whacking

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