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.

 

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