Explore the mysteries of monarchs and milkweeds in your backyard
Published Feb. 17, 2019, in the Wyoming Tribune Eagle.
By Barb Gorges
Monarch butterflies are hard to find in Wyoming. This is partly because we have few people looking for them and because of the terrible decline in monarch numbers. I found a dead one last year. I hope this will be the year I see my first live one in my garden.
That one will be descended from a monarch that’s currently wintering in Mexico (not from the group west of the Rockies wintering in California). It’s the only North American butterfly that must migrate because it can’t survive cold winters like other butterflies.
In spring the generation that wintered in Mexico produces the next generation while on its way north and that one begets another, and so on. After a few months, it may be the fourth generation we finally see here. There are several more generations produced over the summer and the final one makes it all the way back to Mexico in the fall.
Monarchs have been clobbered on both ends of their route. Mexico has established the Monarch Butterfly Biosphere Reserve in the relatively small area they cluster. Here in North America, besides building on and paving over habitat, the problem has been planting herbicide-resistant crops and spraying them with herbicide to kill weeds—which also kills milkweed.
While monarchs feed on nectar from a variety of flowers, they only lay eggs, tiny white dots, on milkweed—it’s the only plant their caterpillars will eat. The good news is that there are about 100 species of milkweed found all along their migration routes. There are 13 species in Wyoming—and four right here in Laramie County.
If you want to join the effort to garden for monarchs, you want to grow our local native flowers. Of course, monarchs are not the only nectar-lovers that will enjoy them.
Two species, Asclepias viridiflora, green milkweed, and A. pumila, plains milkweed, are not seen commercially as seeds or plants. But the other two are quite popular.
Asclepias speciosa, showy milkweed, a perennial, has large round balls of pink florets on stems 2 to 4 feet tall. Its vigorous rhizomes help it spread. I got a few plants from my neighbor who was digging them out of her lawn. But on the other hand, their taproots are sensitive and not all my transplants survived.
I’ve also collected seed from showy milkweed in the unmowed corner of the field where I walk the dog. Seeds are easy to grow if you leave them in the refrigerator for two months to cold stratify or use the winter sowing technique no later than March 1 (https://cheyennegardengossip.wordpress.com/2016/03/21/winter-sowing/).
Plant showy milkweed in full sun for maximum number of flowers. Water it regularly the first summer to get it started. Around the county I see it alongside roads where it gets extra water from runoff when it rains. It is not going to bloom much in a very dry location.
The other local milkweed, Asclepias incarnata, swamp milkweed, I haven’t grown myself yet. Master Gardener Michelle Bohanan assures me that despite its name, it doesn’t need a swamp. Like showy milkweed, it does best with a little more water than just rain to maximize blooms and nectar production. It grows 2-3 feet high, usually with pink flowers, though Michelle has a white variety.
Considering milkweed has been treated as a weed and grows unaided in weedy places, I wouldn’t worry much about fertilizers or compost.
If your showy milkweed gets ugly late in the season, don’t cut it back until there’s nothing left for caterpillars to eat. And even then, the dried plants are useful for catching snow—free winter watering. I cut them back in spring.
All the websites devoted to monarchs say avoid buying plants treated with systemic pesticides. The long-lasting neonicotinoids get in the nectar and poisons the butterfly—and other pollinators. Avoid these herbicide ingredients: Acetamiprid, Clothianidin, Dinotefuran, Imidacloprid, Nitenpyram, Thiacloprid and Thiamethoxam.
Butterflies are also looking for shelter from wind, for sun-warmed rocks and pavement to bask on and for places to puddle on damp sand to get a drink.
The great thing about growing a garden for monarchs is that it also works for bees and birds. But let’s not stop at the garden gate. How about encouraging native flowers along our roads, in corners of fields, in our parks? I’m excited to hear that Nettie Eakes, the head horticulturist at the Cheyenne Botanic Gardens, has plans for more perennials in city beds. Many natives, we hope.
Area milkweed seed sources with growing tips:
Beauty Beyond Belief Wildflower Seed, Boulder, Colorado, https://www.bbbseed.com/
Botanical Interests, Broomfield, Colorado, https://www.botanicalinterests.com/
Western Native Seed, Coaldale, Colorado, http://www.westernnativeseed.com/
Wind River Seed, Manderson, Wyoming, seemed to be out of stock, http://www.windriverseed.com
University of Wyoming Biodiversity Institute, Monarchs and Milkweeds, https://www.wyobiodiversity.org
Monarch Joint Venture (government agencies, non-profits, academics), https://monarchjointventure.org