How To Build The Perfect Monarch Butterfly Garden

monarch on pink flowers

Daniel Potter freely admits he’s not an expert on monarchs. But as Professor of Entomology at the University of Kentucky, he and his grad students sure love to run experiments. Recently, they completed a two-year study on the likes and dislikes of the popular orange and black butterfly. Now for the first time ever, there’s a roadmap for building the perfect monarch garden.

WHY WE CARE

If you’re reading this post, you’re probably already a monarch fan. The butterflies’ annual migration from Mexico to Canada is one of the most spectacular events worldwide. All told, the tiny insects fly upwards of 2000 miles roundtrip each spring, stopping four times to breed and lay their eggs. They are the only butterfly species to make such a long, two-way migration.

monarch migration

Over the past 25 years, however, there’s been a sharp decline in monarch populations. Part of this is due to a loss of habitat at the butterflies’ overwintering site in Mexico. Activities such as logging, agriculture and urbanization have all taken their toll on the central highland forests that play host to the insects six months out of every year.

But by far the most significant factor driving the decline is the dwindling supply of a plant called milkweed. The native wildflower is the only plant that monarch caterpillars will eat. And without it, the butterflies cannot complete their life cycle, sustain their migration and ultimately, perpetuate their species.

monarch feeding on milkweed

MONARCH BUTTERFLY GARDENS NEED MILKWEED 

According to the North American Monarch Conservation Plan, we need 1.8 billion milkweed stems to replace those that have been lost to agriculture and urbanization. And to sustain the annual migration, these contributions need to come from all land sectors. This includes farms, roadsides, schools, zoos and rights of way. And it also includes suburban and urban gardens located along the butterflies’ migratory corridor.

Luckily, an initiative called the Monarch Waystation Program is starting to make a crucial difference. Established in 2005, it engages citizens in conservation by providing instruction and materials on how to build and maintain a monarch habitat. The guidelines are simple: Plant two or more milkweed varieties for the caterpillars to feed on, some nectar sources for the adults, and you become part of a national registry. To date, over 6000 Monarch Waystations in 46 states have become part of the effort. 

WHAT MONARCHS LIKE

And as it happened, the Waystation Program Registry provided the perfect jumping off point for Potter’s research into monarch butterfly gardens. A quick Google Earth search by his team revealed hundreds of habitats scattered along the butterflies’ northward route. What’s more, they represented every kind of landscape.

As Potter put it, ‘Some were non-structured, others ‘wild’, and still others were surrounded by hardscape or located in open rural areas.’ Below are some aerial shots of a few of them. (Photo courtesy Dr. Daniel Potter.)

What Potter and his team wondered was this – with all of this diversity, could there be certain habitats that were more appealing than others? To find the answer, the group decided to survey 22 citizen-planted Waystations. Below are some key outcomes from their investigation. 

1. MONARCHS LIKE STRUCTURE

Like most species, monarchs use visual cues to zero in on what they’re looking for. And in the butterflies’ case, these ‘search images’ are made up exclusively of milkweed. But as the Registry revealed, not all Waystations are the same. Did monarchs favor certain monarch butterfly gardens over others?

Monarchs from ‘search images’ for milkweed

To find out, the researchers counted larvae and caterpillars for a year in their target Waystations to see if the type of habitat made any measurable difference.

monarch caterpillar on milkweed leaf

Monarch caterpillar on milkweed leaf

And they discovered that yes, the butterflies exhibited a strong preference. A structured garden, with milkweed surrounded by mulch, attracted three to five times more monarchs.

The takeaway? If you want more monarchs, make it easy for them to find the milkweed to lay their eggs on. Plant it apart from other plants. Even better, surround it with a mulch circle. But make sure to provide other nectar producing plants nearby for the returning adult butterflies to feed on.

2. MONARCHS PREFER A NORTH-SOUTH ACCESS

Interestingly, the researchers found that gardens with unimpeded north-south access recruited more monarchs. This makes sense since it coincides with the butterflies’ migratory route.

monarch migration map

Monarchs prefer gardens with a north-south access

3. THE TALLER THE BETTER

While all milkweed species are suitable for food, not all are equally favored by monarchs. To find out why, the group compared 8 varieties of milkweed all grown in Kentucky and native to the area. They evaluated them as to their suitability for egg-laying as well as their usability as food for monarch caterpillars. And there was a clear preference.

Where they had a choice, monarchs preferred the taller varieties, Swamp, Common and Showy over the smaller varieties like Butterfly weed

The takeaway? If you want to attract more egg-laying monarchs to your monarch butterfly garden, plant the tall, broadleaf milkweed varieties.

4. MILKWEED CULTIVARS ARE EQUALLY TASTY

But what about all of the new milkweed cultivars, you say? As it has grown in popularity (mainly due to monarchs), milkweed is now available in many cultivated varieties boasting unusual colors and sizes.

Asclepias Gay Butterflies Mix/White Flower Farm

Not to worry. Potter and his students discovered that monarchs find these cultivars just as attractive as the straight species. But again, go with the bigger varieties if you want more monarchs.

5. DON’T LET YOUR MONARCH BUTTERFLY GARDEN BECOME AN ECOLOGICAL TRAP

Finally, there’s the case of tropical milkweed, a non-native plant that has exploded in popularity over the past decade. Both gardeners and monarchs love it. But buyer beware. Tropical milkweed is not ‘bad’, per se, but when planted in warm areas of the U.S. it encourages monarchs to stick around longer. It even enables them to winter-breed.

tropical milkweed

Tropical milkweed, Asclepias curassavica

Research shows, however, that monarchs breeding on tropical milkweed throughout the winter (rather than returning to Mexico) have higher levels of protozoan infection compared to monarchs in the normal migratory cycles. It turns out that migration is key to outrunning these pathogens.

The takeaway? Stick to the tried and true native milkweed species and help the insects keep to their schedule.

To learn more about Daniel Potter and his research into monarchs and other insects, click here for the Dr. Daniel A. Potter Laboratory.

This article was update September 2021.

The Tiny Frog World of the Northern Spring Peeper

These days, even the smallest things can take on greater significance. Like many of you, I’ve been in quarantine for weeks now, except to take occasional walks outdoors. And so it happened that last week, while hiking along Maryland’s C & O canal, I encountered a high-pitched sound. The single, repeated note seemed to be emanating from the forest. Continue reading

Feed The Birds: 10 Plants With Great Winter Seedheads

Once flowers dry up in the vase, we tend to throw them in the garbage. But outdoors, it’s a whole different story. Not only do the seedheads of spent flowers bring beauty to the garden, but they also furnish food to hungry birds and wildlife. And those two reasons alone should cause us to think twice before we start cutting our plants back for the winter. Continue reading

Nurturing Wildlife Habitats: Five Ways To Save the Planet

For many of us, attracting wildlife to our gardens sounds good in theory but fails in practice. Especially when it comes to that four-legged pest the white–tailed deer. However, there are many sound reasons for enticing birds, insects, even small animals back into our yards. It’s not only good for our local ecosystem, but it also keeps our flowers blooming. And it just might be the right thing to do. Continue reading

What Dirty Old Birds Can Teach Us About Air Pollution

Bird specimens at the Field Museum of Chicago

It couldn’t help but attract my attention; a neat row of old, preserved birds, their soft, feathery chests face-up: some were dark with soot, others by comparison, were clean. All came from an industrial area in the United States called the Rust Belt. That is key to the story. Continue reading

Now There’s Proof: Bumblebees Make Bigger Plants

Bumblebee pollinating mustard plant/ Photo: University of Zurich (UZH)

In recent years, there’s been a lot of buzz about pollinators, especially the fuzzy yellow and black kind. Now comes news that bumblebees not only help plants propagate, but they also have a positive effect on their size, fragrance and color. It’s all part of an experiment by researchers at the University of Zurich that proves bees do it bigger and better. Continue reading

New Study Reveals Ants Know How To Grow Plants

fiji-ant

“Even the sharpest ear cannot hear an ant singing” -Sudanese Proverb

(Red ant on Fijian palm leaf)

Just when you thought you’d heard it all, this week comes the revelation that a certain species of Fijiian ants has been growing plants for millennia.  And they’ve been doing so for far longer than humans. The ants have been growing crops and establishing their colonies within them all while tending their own teeny tiny community gardens. Continue reading

The Return of the Purple Martin

pm.cover

As all gardeners know, working in the garden is not just about plants. Being outside with your hands in the soil makes you keenly aware of animal life, too. Over the years, I’ve gardened in tandem with a majestic blue heron, a band of three crows and a playful red fox. Now, with the arrival of warmer weather, I’m looking forward to the return of the purple martins.

Aside from being able to identify their houses (virtual mansions of the ornithological kind), I didn’t know much about these birds until recently, when my garden club hosted two members of a local purple martin society. Ever since, I’ve been scanning the skies for the colorful species. According to the experts, the first wave of birds will be arriving in my area soon.

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Purple martin house

PURPLE MARTINS HEAD NORTH IN THEIR ‘WINTER’

Of the eight swallow species, purple martins are the largest. The dark, bluish-black birds arrive in North America each spring, soaring on the jet stream from their native southern Brazil. It takes them about five weeks to fly the 10,000 miles, which is quite a feat for a bird that weighs only about 2 ½ ounces.

pm.female in flight

Female purple martin in flight

Like many neotropical birds, purple martins travel north in order to breed. The birds arrive at the height of the insect season, establishing themselves in colonies located close to water where there is the greatest food supply. In total, the migration can take up to 2 to 3 months to complete.

ONLY MAN-MADE HOUSING WILL DO

In Brazil, purple martins are considered a public nuisance, mainly due to their large numbers and preference for roosting in trees around central plazas. As a result, some municipalities have gone so far as to install sirens and other devices to chase the birds away.

In the United States, on the other hand, it’s a different story. Here, large groups of purple martins return each year to establish neighborhoods in man-made housing only. In fact, they are the only bird species that is totally dependent on human-supplied housing. Not only do they like people, but they actually prefer living in close proximity. 

Purple Martin Birdhouse Community

As a species, purple martins favor locations in wide-open terrain, usually in the form of pole-mounted martin houses or gourds. This keeps them out of reach of predators like owls and hawks that dwell in tree cavities. They’ll generally avoid congested suburban areas and instead roost in open meadows or fields located near lakes or other bodies of water.

Although just one male and female live together in a room or gourd, the highly sociable birds house together in colonies, where they interact as a unit, sharing food and singing to each other. All told, a group of houses or gourds can host as many as 60 to 70 birds over a 2-month period.

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Purple martin pair

THEY SEND SCOUTS

Now is the time of year when the first scouts (who are the oldest birds) begin arriving from Brazil to check out their nesting sites from the previous year. The scouts pave the way for the rest of the flock, which arrives 4 to 6 weeks later. Built like a glider, the birds can travel at speeds of more than 40 miles per hour.

THEY ONLY FEED ON THE FLY

And purple martins bring a whole new meaning to eating ‘on the fly.’ According to Mike Dickson of the Purple Martin Society of Frederick, Maryland, they only recognize food that is in flight, meaning that they primarily snatch insects in midair. Adept in performing complex aerial acrobatics, the birds even drink in the air. They accomplish this by flying low over lakes or ponds while scooping up water with their bills.

pm.female in flight 2

A female in flight

Indeed, you’ll never find purple martins foraging for food on the ground, or eating seed from a feeder. People who choose to feed the friendly birds will discover they’re quite open to the idea, but only if the food is flung to them. On occasion, human intervention is necessary when periods of cold or rain suppress insect populations. This can spell death to entire colonies.

THEY SING REALLY WELL

One of only a few colony birds that love to sing, purple martins’ throaty chirps can be heard May through June during the breeding season. According to the Cornell Lab of Ornithology, males make a croaking song during courtship that can last up to 4 seconds. People say that once you’ve heard it, you’ll never forget it.

pm.male standing on post in British columbia

Males perform the dawn song

Purple martins sing in a combination of gurgles, clicks and song, with the loudest singing occurring before daylight. Males perform this dawn song possibly to attract other birds to the nesting site. Click here to hear a few of their beautiful songs.

AN EARLY DEPARTURE

All too soon, by the end of July or first week in August, the birds prepare to leave for their migratory roost. Many purple martin lovers describe this time as a sad one, when they awake to find the birds gone and their houses empty. It’s as if suddenly, the countryside has fallen silent.

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Female purple martin

Once airborne, the birds fly south to a designated spot to roost before heading back to Brazil. Often they gather by the tens of thousands. In fact, the largest roosting colony on record was estimated to have 700,000 birds at one time. All told, there can be thousands of purple martins in the sky at one time, so many that they often show up on Doppler radar as giant rings.

Interested in attracting purple martins? Here’s a great article from the Purple Martin Conservation Association in Edinboro, PA, a non-profit conservation organization.

 

 

Bee ID: How To Make Sense Of The Buzz In Your Garden

cover.bumble bee

Aren’t they cute?

One of the many things I love about gardening is working alongside my many fuzzy, buzzing friends. Dutifully arriving on the job each morning, the bees hover beside me, yielding as one mass each time I shift position in the garden. Sometimes, I’ve been brave (or stupid) enough to touch one of the downy creatures, and they’ve allowed me to stroke them. Feeling the tiny vibrations of all that industriousness never ceases to amaze me. Continue reading