Monarchs and Milkweeds

monarchs and milkweedsmonarchs and milkweeds
By Judith Irven, gardening expert, landscape designer and writer.

Beautiful garden visitors with an ingenious defense against predators

The gorgeous American Monarch butterflies (Danaus plexippus), with their orange wings, black veining and a distinctive black and white checkered pattern around the margins, are instantly recognizable by gardeners and non-gardeners alike.

Not so long ago, every year in late summer, dozens of Monarch butterflies would visit our Vermont mountain garden. Seeking the nectar, adult butterflies flocked to the Shasta Daisies, Blazing Star, Echinacea, Rudbeckia, Asters, and—always a huge favorite among all the butterflies—the ornamental Oregano. They also spent time in the meadow across the road where they feasted on the wild Milkweed, Goldenrod and Asters.

As a defense against predators, Monarch butterflies contain unpalatable chemicals that can actually cause some birds to vomit! And their bold wing pattern is a well-known warning to hungry birds that they should not trifle with those Monarchs.

But in the past ten years, we may see only two or three of these beautiful butterflies in our garden. Indeed there were a couple of years when we did not see a single Monarch! And this precipitous decline has been repeated all across the country.

By current estimates, the overall number of American Monarchs has fallen by 90% in the last decade. The decline of Monarchs is directly linked to the loss of milkweed plants in the wild.

This is because milkweeds (all members of the genus Asclepias) are the host plants for Monarchs - they are the ONLY PLANTS that Monarch larvae are able to eat. Their ingenious defense against predators—the unpalatable taste of both caterpillars and adults—is derived from the chemicals contained in the milkweed plants.

Today, before beginning their spring planting, many farmers will spray their fields with chemicals to eradicate weeds. But inadvertently this practice also kills all the wildflowers, including the Milkweeds, that surround those fields.

The amazing life cycle of the American Monarchs: If we are to reverse their appalling decline, it is helpful to understand more about of the remarkable life story of the American Monarch. There are actually several populations of American Monarchs, and the two major populations, the Eastern Monarchs and the Western Monarchs, are famous both for their distributed breeding patterns and for their legendary long distance migrations.

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two monarchs on butterfly weedtwo monarchs on butterfly weed
A cluster of Monarch Butterflies on Butterfly Weed.

 Monarchs and Milkweeds From East to West

Eastern Monarchs

In the summertime Eastern Monarchs can be found all the way from Mexico to southern Canada and from the Rocky Mountains to the Eastern seaboard. And, all across this huge land area, four or sometimes five generations of Monarchs are born in a single season.

Then, starting in September and October, all Eastern Monarchs, (with the exception of a few that use the Atlantic seaboard) undertake a single prodigious migration to reach their over-wintering destination, the Monarch Butterfly Biosphere Reserve, in Southern Mexico.

And, during this migration, these tiny creatures fly the most astonishing distances—those that begin their journey in the Canadian Maritime provinces will travel nearly five thousand miles—to reach their winter destination in Central Mexico. Butterflies begin their fall migration in September or October, and finally reach their overwintering sanctuary in November.

Then the following March those same butterflies set out on their northbound trip. However no individual butterfly flies all the way north. At successive stops along the way the female monarchs lay eggs on there milkweed plants, and the resulting caterpillars initiate the new generation of butterflies that continue the journey northwards. It is estimated that, in the course of the entire summer, eventually four or five generations will be raised.

But, in early fall, the final generation of females, instead of producing more eggs, is programmed to store their food supply in preparation for their long flight back to Mexico. And these butterflies are also programmed to fly south or south-west depending on their starting points, to reach this single destination.

Check out this wonderful interactive map to see the flight paths taken by the butterflies, both during their trip south in the fall, as well as how the successive generations that are raised on the way north in the course of a single summer.

Thus, if humans are to halt the decline of the Monarchs, we need to ensure that milkweeds and other nectar producing flowers are available for the butterflies at each breeding point along their journey.

Western Monarchs

Like their eastern counterparts, the Western Monarch butterflies also have a migratory life-cycle. Their summer territory is to the west of the Rocky Mountains, where typically they will hatch three generations at successive points along those fly-ways.

Then every fall, the third generation of these butterflies is programmed head south-west to reach one of several over-wintering destinations along the west coast of California and western Mexico.

Non-Migratory Monarchs

Unlike the Eastern and Western populations, the American Monarchs that are found in Florida and along the gulf coast do not migrate. Instead this populations remains in place on a year-round basis.

 

Milkweeds: The Critical Link For Rebuilding our Monarch Populations

As we remember: the larvae of the butterflies absolutely require milkweed to survive. For the Eastern and Western migratory Monarchs, the butterflies that lay their eggs at successive breeding points during their summer journeys, we need to ensure there are milkweeds at each breeding area along the fly-ways.

Learn How to Create a Monarch Waystaion with Milkweed and Nectar Plants

The non-migratory populations around the gulf coast and in Florida also need milkweeds in their breeding areas.

Reversing the decline of the Monarchs

Today the milkweeds are starting to make a come-back all across the country. As of 2016, the USDA is offering incentives for farmers and ranchers to plant milkweed and other pollinator friendly plants.

And private citizens are also rallying to help the beleaguered butterflies. Since milkweeds make great garden plants, many gardeners and schools are experimenting with planting them. And many people with larger properties are planting milkweeds as part of a naturalized meadow.

But, for this effort to be truly effective, there can be no weak links in the chain. Milkweed restoration is required at each and every breeding point of these wonderful migratory butterflies.

 

 


About the Author: Judith Irven is an accomplished Vermont landscape designer and garden writer, and she delights in helping people everywhere create beautiful gardens. You can visit her online at: OutdoorSpacesVermont.com.

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monarch caterpilla on a tropical milkweedmonarch caterpilla on a tropical milkweed
A growing Monarch caterpillar hungrily gnaws on tropical milkweed.
caterpillar crawling on milkweedcaterpillar crawling on milkweed
With many predators, only a small perecentage of Monarch caterpillars survive and become butterflies.
fake wasp nestfake wasp nest
A 'fake wasp nest' keeps the milkweed patch safe from dangerous predators.
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