Monarchs: The Fall Migration
- Jennifer Anderson
- Aug 11
- 4 min read
Yes, I've been to Mexico, with help from maps, pilots and other resources handed down from generations of people who've been there before.
Not so for Monarch butterflies. Every new generation, every year, is a first-timer to Mexico. Not just anywhere in the country, but to the exact spot where their ancestors landed.
No one fully understands how they know where to go.
The position of the sun, the Earth's magnetic field, or a combination, are all likely factors.
A lot remains unknown.
It all starts mid-summer with the birth of the Super Monarchs. These adults, just out of the chrysalis, are different from other Monarchs. They're not interested in mating or egg-laying; instead, they're jazzed to hit the airways.
Along the way, they fuel up — slurp nectar — from native plants.
Why Mexico?
Scientists believe Monarchs originally
were tropical butterflies but gradually
expanded their range as the milkweeds moved north.
They’re fine most of the year but cannot survive the freezing winters of the northeastern United States and Canada. Mexico's high-altitude central highlands offer just the right conditions for the butterflies to semi-hibernate until spring.
No one knows for sure how long Monarchs have been making the journey, but some scientists suggest it could have started as many as 10,000 years ago.
Life Cycle
Not all Monarchs migrate. Most Monarch butterflies live for only up to five weeks and lay lots of eggs.
These Monarchs are born throughout the spring and summer.
Around mid-summer, in addition to regular Monarchs, the Super Monarchs also emerge from the chrysalis. These Super Monarchs look like regular Monarchs but live much longer: 8 to 9 months. In exchange for longevity they forgo mating (for the time being) and instead focus on bulking up for the flight south.
How Do They Do It?
Super Monarchs enter the world in a state of reproductive diapause, brought on by their extreme sensitivities to changes in daylight, possibly the way the milkweed tasted when they were caterpillars, subtle changes in nighttime temperatures — and probably other things no one has figured out yet.
Monarchs in diapause do not want to mate or lay eggs. Instead, they put all of their energy into the 2,000- to 3,000-mile journey ahead, flying at altitudes sometimes up to a mile high and catching rides on air currents.
Destiny: Mexico
Once in the
Transvolcanic
mountains of
central Mexico,
usually by early
November, the
Monarchs crowd together on south-facing slopes and trees. There, they rest and conserve energy until spring and warmer weather.
Reproductive instincts kick in as diapause ends, maybe in March or April, and the Monarchs start the trek back north. They might make it to Texas, where they look for milkweed, mate, lay eggs and lay down their lives.
Their offspring continue the journey north, reproducing along the way and living, again, up to five weeks per generation.
The grandchildren, or great-grandchildren, of those born in Texas will eventually reach New England — just as the milkweed plants are sprouting new leaves. 🍃
Seeing More Monarchs? 🦋 👀 You're Not Imagining It
Eastern Monarch populations showed a 64% increase in overwintering habitat in 2026 — the second consecutive year of increase, according to the World Wildlife Fund and Mexico's National Commission of Protected Natural Areas.
It's too soon to get complacent. Despite the bump, the U.S. Fish and Wildlife Service estimates eastern Monarchs face a 56% to 74% chance of extinction by 2080.
"Round[ing] up the usual suspects" (Claude Rains, Casablanca, 1942):
Habitat loss
Pesticide exposure, and
Climate change
all are threatening the Monarchs' long-term survival.
What We Can Do
Monarchs need nectar, especially for their journey south. Late-summer native nectar plants — goldenrods, asters, Joe Pye Weed, New York Ironweed, sunflowers, Black-eyed Susans, Field Thistle — are among the best plants for Monarchs seeking fuel for the journey to Mexico. Check your garden! If you don't have these plants, think about where you can fit them in.
Milkweed
Monarchs need plants on which to lay their eggs. The menu: Milkweed!
The only plant suitable for Monarch caterpillars is Milkweed. This dynamic plant also provides nectar for adult Monarch butterflies.
There are a few types of Milkweed native to New England. Each has its own personality:
Swamp Milkweed (Asclepias incarnata) — Fragrant pink blooms, loves moist soil, a Monarch favorite.
Common Milkweed (Asclepias syriaca) — The most attractive to Monarchs overall, for both nectar and egg laying. Aggressive spreader; not recommended for small areas.
Butterfly Milkweed (Asclepias tuberosa) — Brilliant orange blooms, drought tolerant, excellent nectar source. Monarchs will lay eggs on it when other milkweeds aren't available.
At Tree Talk Natives, we're here to help you plan a garden for Monarchs.
We can advise on individual plants or, if you're starting from scratch, we've put together a kit you might find useful. Our kit includes just about everything you need to create a Monarch Waystation in your own garden — native nectar plants and milkweeds selected specifically to support Monarchs on their journey.
Whatever you choose, the best path is to get started. Every garden counts. The Monarchs need our help beating the odds. 🦋
*Photo: Erin Minuskin
About the author
Jennifer Anderson owns Tree Talk Natives, a native tree and plant nursery along Massachusetts' South Shore. A former news reporter, she loves to write and talk about native plants. Jennifer also gives garden consultations and presentations on native plants. She can be reached at jennifer@treetalknatives.com.
Sources:
Annual Cycle. Monarch Butterfly Fund: Conserving the Migration
Arroyo, K. “…how some Monarch butterflies live longer than others? (with Isis Howard),” Ever Wonder? California Science Center. Interview with Isis Howard. April 10, 2024.
Howard, I. and Kailee Slusser 5 Monarch Migration Facts. Xerces Society. February 6, 2025.
Koenig, M. The monarch super generation and their phenomenal migration
Migration. Monarch Joint Venture
Monarch butterfly population increases by 64%. World Wildlife Fund. March 17, 2026
Save the Monarch U. S. Fish and Wildlife Service. July 23, 2026
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