monarch butterfly

The monarch butterfly (Danaus plexippus) is one of our most iconic pollinators, known for its large size, bright orange color, and impressive fall migration to Mexico. Yet the monarch’s recent listing as endangered on the IUCN red list has led many to wonder what steps to take to help the monarch in their own yards. Read on to learn TPI’s advice to those looking to help monarchs and for a guide to noticing the different life stages of monarchs in your garden.

1. Plant milkweed

As caterpillars, monarch butterflies can only feed on milkweed (plants in the genus Asclepias), meaning these host plants are necessary for the monarch’s survival. There are several species of milkweed native to the northeast, including common milkweed (Asclepias syriaca), butterfly weed (Asclepias tuberosa), and swamp milkweed (Asclepias incarnata). Butterfly weed and swamp milkweed both perform well in gardens – the former preferring dry soils and the latter preferring wetter soils – and can be found at most garden centers. Swamp milkweed also has shallower roots, which means it can grow well in a container if garden space is limited.

2. Plant nectar-rich flowers

Unlike the caterpillar stage, adult monarchs are not limited to milkweed and feed on a wide array of plants for nectar. These sugary resources extend their lifespan and give them the energy to fly farther and make more offspring. TPI has many resources to help you make your garden even more friendly for monarchs and other pollinators, including plant lists, a guide on how to leave swamp milkweed stems for bees and this blog post!

3. Don’t take eggs or caterpillars off of plants

Although it is tempting to take in any eggs or caterpillars you see to keep them safe and watch them grow, it can actually do more harm than good. Rearing large numbers of monarchs inside can increase the incidence of disease within the population. And, even worse, recent research has shown that monarchs reared indoors without natural environmental cues are less able to migrate south in the fall. While raising monarchs can be a great educational experience, we recommend instead making a daily habit of watching the progress of the wild eggs and caterpillars you find in your garden (See below for our guide to finding monarchs in the garden!).

4. Don’t apply pesticides to your garden

Milkweed plants often become infested with tiny orange aphids (Aphis nerii). Do not worry–this is a totally natural occurrence and won’t hurt the monarchs. Aphid infestations can be unsightly but refrain from using pesticides as this will harm the monarch caterpillars. To remove aphids, use natural methods like a spray of soapy water. Natural predators such as ladybugs, lacewings, and their larva will also take care of the aphids!

Oleander aphids (*Aphis nerii*) on swamp milkweed (*Asclepias incarnata*)

How do you know if you have monarchs using your garden?

Monarchs are easy to spot as adults but we don’t see them as frequently as caterpillars. Here are some tips on identifying monarch presence in your garden:

Adults

Adult monarch butterflies are highly conspicuous––look for a big orange butterfly with black veins. They glide around with their wings held in a “V” and visit gardens to lay eggs on milkweed and drink nectar from flowers. Similar looking viceroy butterflies are smaller and hold their wings flat when they glide. Monarchs like a variety of garden flowers for nectar including purple coneflower, swamp milkweed, joe-pye weed, mexican sunflowers, and zinnias.

Adult female monarch ovipositing (egg laying) on swamp milkweed (Asclepias incarnata)

Eggs

Monarch eggs are sesame seed sized, a creamy white color, and slightly pointy–like a tiny hard boiled egg. These eggs are singly laid, meaning there is only one egg instead of a mass of many eggs. Monarchs tend to oviposit on the underside of leaves, but eggs can also be found on other parts of the plant, especially the flower heads. If you want to find eggs, patiently search the undersides of leaves and flower heads, especially focusing on the tallest areas of the milkweed, where monarchs tend to land. It may take a few days of checking before you see an egg, but don’t be discouraged! Even if you don’t see a monarch laying eggs on your plants, your garden may still have them–an adult monarch can lay an egg in under 5 seconds! Lastly, remember that although monarchs can start appearing in our region (MA) as early as the start of May, they are not widespread until late June, so time your searches for July-August if you want the best chance of success.

Closer look at a monarch egg, PC Jay Cossey

Caterpillars

Monarch caterpillars hatch in 3-5 days and eat their very first meal: their eggshell! These baby caterpillars are very small and difficult to spot. They are vulnerable at this stage to hungry insects like paper wasps. As they eat milkweed leaves, the caterpillars grow bigger and molt through stages called instars. You can tell a caterpillar’s approximate age by identifying its instar – monarch caterpillars go through five instars before pupating. Most of the caterpillars we find in the wild are small (in their first or second instars): due to the high rates of predation on these small stages, it’s less common to see large caterpillars.

First instar monarch caterpillar eating its egg

While these small caterpillars can be difficult to spot, their feeding damage can be more apparent: it takes the form of small ‘windows’ into milkweed leaves, half-chewed holes often carved into a small circle, which the caterpillar uses to avoid drowning in the milky latex exuded by its host plant. If you see frass (caterpillar poop: poppy seed-sized brown pellets) or large missing chunks from the edges of the milkweed leaves, then be on the lookout: these are the telltale signs of a much larger stage 4 or 5 caterpillar! Be sure to check under the leaves, as caterpillars of all stages prefer to eat from beneath the leaf, where they are more sheltered.

Small black frass surrounding a second install caterpillar

Pupa

Monarch pupa are hard to spot as they blend into the surrounding environment. The 5^th instar caterpillars tend to crawl away from the milkweed to pupate on nearby plants. They will remain in the pupa for 7-10 days before emerging as a beautiful monarch butterfly.

Have you found monarchs in your garden? Share your photos to @pollinatetufts!

A migrating monarch feeding on seaside goldenrod in Gloucester, MA. PC: Rachael Bonoan.

Fall is a time for migration in the North, as animals flee the bitter cold of winter in favor of warmer regions. If you’ve been outside in New England in the past few weeks, you’ve probably been in the presence of these migrants. Birds are some of the best known long-distance migrants, but plenty of insect pollinators embark on similarly stunning journeys each fall, in spite of their diminutive size. Some are inconspicuous and elusive, like the various species of hover fly whose migration through our region has only been recorded a few times in the past hundred years; others, like the monarch butterfly, are beloved signs of the closing of summer.

Each fall, millions of these large orange and black butterflies form a remarkable caravan, as monarchs from breeding grounds across a range that stretches as far north as Nova Scotia embark on the long flight to the overwintering grounds in central Mexico. These migratory monarchs need to reach dwindling undisturbed patches of oyamel fir forest, where they spend much of the cool winter perched in massive clumps on the trees, largely quiescent. There they wait for warmer temperatures that signal the arrival of Spring, when they can depart and gradually begin their multi-generational recolonization of the breeding range.

Surviving the 3000+ miles of flight and the subsequent months of cool winter in Mexico requires energy, and lots of it. The butterflies – weighing about a fifth of a penny – bulk up on nectar by gorging for hours on fall-blooming flowers. So efficient are their digestive systems that it’s thought that the sugars in the nectar can be converted into energy-rich fat stored in a special organ in a matter of minutes. Monarchs most likely need to more than double their regular fat stores during migration in order to survive the winter, meaning that stunningly, these butterflies actually gain weight during their multi-thousand-mile-journey.

Two migrating monarchs on an aster species (*Symphyotrichum* sp.). In the fall, males and females are non-reproductive; they happily feed on the same plants and often roost together during migration. PC: Rachael Bonoan

You may have heard that monarch butterfly populations have suffered steep declines in recent years, with most estimates putting the losses in the Eastern population over 80%. A broad set of human actions have conspired against the monarchs, including deforestation in Mexico and agricultural herbicide use in the Midwest. Recently, ecologists have raised the specter of a third challenge: increased mortality during migration.

Migration is a dangerous undertaking, and biologists speculate that perhaps as many as 95% of monarchs attempting to migrate perish each year. As meadows and prairies have been converted to asphalt and crops, native grassland habitats that support large numbers of fall-blooming flowers are a dwindling commodity. Some ecologists posit that a lack of nectar along the migration route could be leading to starvation during the flight or in the quiescent overwintering period.

This is where we come in. Through planting gardens that can continue producing flowers all the way through October, we can provide valuable resources not just for monarchs but for all the other pollinators that are still flying. Surviving and thriving at this time of year in New England can be a tenuous proposition for animals that eat nectar and pollen: nighttime temperatures flirt with freezing and many of the flowering plants in our region have already gone to seed or begun senescing by September. In a summer with a drought like the one we’ve had in Massachusetts this year, wildflower outlooks can be even grimmer by the time October swings around.

But where there is a tenuous situation, there is also an opportunity for our interventions to make a bigger difference. Much of the land in New England would, given the chance, burst into late-fall bloom every year in a riot of goldenrods and asters, pumping out nectar and pollen through until frost. These native, pollinator-friendly species are conveniently often exceedingly drought-tolerant and some grow aggressively when given the chance, like the goldenrod species in the picture below:

A vacant lot in Rhode Island, September 2020, brimming with goldenrod. PC: Atticus Murphy.

Crucially, these patches can arise in the middle of neighborhoods on vacant lots or road verges, providing unexpected oases for fall-flying insects. Likewise, by carefully planning gardens that bloom continuously until the end of September, gardeners can provide nectar not only for migrating monarchs, but the hundreds of other pollinator species that require pollen during the fall.

Adding autumn-blooming flowers amounts to starting a food bank for pollinators like monarchs, and by planting easy-to-grow native perennials like goldenrods and asters, the food bank will return every year, essentially for free! Migration is hard enough without pesky human interference; let’s try and help these iconic butterflies along their way, if we can.

Tag: monarch butterfly

How to help the monarch butterfly