Monarchs Arrive in Europe!

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Monarch butterflies, once strictly limited to the New World, are now found in Europe too. Source: Kenneth Dwain Harrelson, Wikimedia Commons

The famous migratory butterfly, the monarch (Danaus plexippus), is native to North and Central America and northern South America. (Elsewhere in South America, it is replaced by the southern monarch [Danaus erippus], a similar but essentially non-migratory species.) But, while the adult butterfly can feed on the nectar of a wide range of flowers, the larva of this species is extremely limited in its food sources. It can consume only milkweed leaves (Asclepias spp.), a genus originally limited to the New World, as well as those of its next-of-kin, the false cotton bush (Gomphocarpus spp.), originally from South Africa. However, the monarch never managed to find the way to South Africa. So, for tens of thousands of years, the monarch was strictly limited to the New World where milkweeds abound.

Expansionist Ideas

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The narrow leaf false cotton bush (Gomphocarpus fruticosus) is one of the food plants that have allowed the monarch to settle in new territories. Source: Xemenendura, Wikimedia Commons

That’s no longer the case! Humans have planted various species of false cotton bush and milkweed as ornamental plants, and a few have become naturalized well outside of their natural range. Tropical milkweed (Asclepias curassavica) and narrow leaf false cotton bush (Gomphocarpus fruticosus), for example, are well established in most subtropical regions around the world and that’s been the case since at least the beginning of the 19th century.

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Monarch butterfly distribution today  . Source: monarchlab.org

The northern monarch (D. plexippus) has taken advantage of the widened distribution of its host plants to expand its range. It first established a foothold in the Hawaiian Islands in the 1840s and from there spread throughout the islands of the South Pacific in the 1850s and 1860s. It first appeared in Australia and New Zealand in the 1870s and is now firmly entrenched in both countries, even fairly common in some areas.

So much for the Pacific. It somehow crossed the Atlantic as well, first showing up in the Canary Islands, off the coast of Africa, in the 1880s, then spreading to other islands in Macaronesia (Madeira, the Azores, etc.).

By Wind, Wing or Sail?

No one knows for certain how this dispersion took place. Did the butterfly travel as a stowaway on boats from one continent to another? Did it fly on its own? (Since adults can travel 1,400 miles [2,200 km] in the wild, that’s far from impossible). Or were they carried across oceans by the wind? We may never know.

Now Continental Europe

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Monarch butterfly and caterpillar on tropical milkweed (Asclepias curassavica). Source: www.jungledragon.com

Monarch butterflies have been showing up sporadically in Europe for hundreds of years, but at first, showed no inclination of trying to settle down permanently. Then in 1980, a population of monarchs was found naturalized in southern Spain (Malaga) and it has since spread along the west coast of Portugal and the southern coast of Spain, two regions where tropical milkweed (Asclepias curassavica) and narrow-leaf false cotton bush (Gomphocarpus fruticosus) are well established. It is also seen in summer and early fall in France and the British Isles. In fact, one female laid eggs on a milkweed in Kew Gardens in London, but the gardeners there brought them indoors to hatch, so the next generation never had a chance to start a local generation.

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Butterfly weed (A. tuberosa) is a hardy species that is grown as an ornamental in Europe, but probably not extensively enough to support a local population of monarch butterflies. Source: Aaron Carlson, Wikimedia Commons

Indeed, the monarch butterfly may never be able to fully settle in temperate Europe due to the lack of cold hardy milkweeds there. Some hardy species are now being grown as perennials, but only in gardens. Butterfly weed (A. tuberosa) and swamp milkweed (A. incarnata), for example, are known to European gardeners, but have not naturalized, which limits the possibilities for breeding monarch to settle there permanently.

Still, the many European readers of this blog can monitor the presence of this insect in their gardens in summer and early fall. The monarch is easy to recognize not only because of its flamboyant orange color with black veins, but also because it is the largest butterfly in Europe.


Whether the monarch only maintains a tenuous foothold in Europe or fully establishes itself remains to be seen. And whether its presence on European soil is a good thing or not is also questionable. Only time will tell!

Monarch Butterflies are Back!

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Monarch butterfly numbers are up this year.

Congratulations, butterfly gardeners! You’re obviously doing a good job, since the monarch butterfly (Danaus plexippus), whose numbers crashed drastically in 2013, are up… in a big way.

You may recall the glum news in 2013-2014. Never had so few monarch butterflies reached their wintering grounds in the fir and pine forests of Central Mexico. Only 0.67 hectares of forest were covered in monarchs that year, for a total of some 33 million monarchs, the lowest number ever, and experts were concerned that the era of the migrating monarch was nearing an end.

20160324CEnglish.png Fortunately, numbers picked up considerably in 2014-2015 and jumped massively this winter (2015-2016), covering 4.01 hectares for an estimated 140 million monarchs. While this is still 30% below the long-term average of 6 hectares, it is still a massive improvement and corresponds to about the average number this century.

What Happened?

The crash of the 2013 was due largely to poor weather. Drought conditions, first in Mexico, then in the Southwestern US, drastically cut back on the number of monarchs that were able to reproduce. (Monarchs move northward generation by generation from spring through mid-summer and at each stage along their route, they need a healthy food source of their only food plant, the milkweed [Asclepias spp.] and drying, desiccated plants won’t host many larvae!) Therefore, fewer monarchs made it past the drought zone to more northern climes…

… And those that did found less food for their caterpillars than ever. The increasing efficiency of modern farming, which leaves no space for native plants, including milkweeds, is seriously hampering the creature’s ability to reproduce. Their caterpillars can only live on milkweeds and if the number of available milkweeds continues to drop, the monarch’s survival as a migrating species will remain critical.

20160324F.pngLast summer (2015), the weather couldn’t have been better. Where milkweeds still do grow, they were well-watered and healthy all across the monarch’s route north, just what they need to reproduce abundantly. Plus the news that monarchs need milkweeds as a food source is becoming common knowledge, thanks to programs like the Million Pollinator Garden Challenge, and gardeners across North America are planting milkweeds, many of which are attractive garden plants, in increasing numbers. Governments are helping too. The US, for example, has restored over 100,000 hectares of fields without pesticides in order to save the monarchs, at a cost of over $20 million.

Goal of 250 Million Monarchs

The monarch population has always been unstable. Numbers go up and down according to all sorts of factors. However, if we’re congratulating ourselves about 140 monarchs this year, that number would have seemed disappointing 20 years ago, when 250 million monarchs was considered the average. Many associations from Mexico to Canada have made that their goal for 2020: to reach an average overwintering population of 250 million monarchs again.

Much still has to be done… and not all of it is within the grasp of home gardeners. Illegal logging in the monarch’s wintering grounds in Mexico remains a threat you can’t do much about, for example. And it’s hard to convince farmers to leave space for few native plants. But at least anyone can plant milkweeds.

Milkweeds for Your Garden

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Asclepias tuberosa

Butterfly weed (A. tuberosa) is a stunningly beautiful milkweed with bright orange to yellow flowers that you could be growing in your garden, for example. It likes full sun, well-drained to dry soils and will grow in USDA hardiness zones 3 to 9 (AgCan zones 4 to 9).

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Asclepias incarnata

It doesn’t thrive in my rainy climate, but the swamp milkweed (A. incarnata), with pink or white flowers, certainly does. It is just as hardy, perhaps even moreso… and in spite of its name, it doesn’t need to grow in a swamp, but is instead perfectly happy growing in full sun under average garden conditions. And yes, I did have monarch caterpillars on mine last summer after two years in which I saw no monarchs whatsoever.

Note that neither of these plants are invasive. They’ll grow in a dense clump and stay where you plant them. They are each, in their own way, ideal plants for laidback gardeners.

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Asclepias curassavica

You don’t have a garden? Well, perhaps you have a balcony. If so, you could grow plants of tropical milkweed (A. curassavica). This plant, grown as an annual in the North, is actually the monarch’s main food source in Mexico, where it grows wild as a perennial. It has bright orange flowers with a yellow center. It grows readily from seed and will bloom the first summer if you start it indoors. After a summer outside, you can then bring it indoors as a houseplant in the fall if you want to. If you can’t find seeds locally, I know of at least two mail order sources, William Dam Seeds and Richters Herbs, that sell them.

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Monarch caterpillar

If you find leaves being chewed on your garden’s milkweeds, you’ll know you’ll have succeeded. Look for a rather bizarrely striped caterpillar: a future monarch butterfly. Congrats! You’ll have done your part to save this fascinating creature!

From the Far End of Its Range

Where I live in Quebec City is pretty much as far north as monarchs ever go. When they’ve made it here, you know it’s been a good year. I’ve also been lucky enough to have seen the monarchs overwintering in a Mexican forest, a sight (and sound, as the millions of fluttering wings give off a sort of soft murmur) I’ll never forget. So I encourage every North American gardener reading this blog to plant at least one Asclepias this summer. It’s just one more plant to add to your garden palette, yet such a simple choice can have a huge impact on the monarch’s survival.