Here in Western North Carolina, there are journal entries from the turn of the century describing how monarch butterflies blacked out the sky during their fall migration to Mexico. But this spring and summer, consider yourself lucky if you see a monarch butterfly or two. If you’re incredibly lucky, a monarch butterfly will lay eggs on your milkweed. Monarch populations east of the Rockies are down at least 80% since the 1980s. Even worse, monarch populations west of the Rockies are down 99%.
Planting milkweed for them to lay their eggs on and not using pesticides is more vital than ever to bringing them back.
In the fall, a single young insect that weighs the equivalent of a raisin may fly south all the way from Ontario, Canada, to the high oyamel fir forests of central Mexico—3000 miles! That astounding feat continues to be one of the world’s great wonders. In Mexico, those same “super” butterflies will rest in a state of diapause through the winter, mate around Valentines’ Day, and then remarkably migrate northward through Texas to the Midwest and eastern United States, laying their eggs on young milkweed along the way. It will take three-four generations to reach Canada.
They are being spotted in Asheville right now, which means they almost certainly overwintered in Mexico, 2000 miles away from Asheville. Hopefully you planted your milkweed (their only host plants for their caterpillars) last fall or winter and it is coming out of the ground right now ready for the hundreds of pearly white eggs the females will lay.
Monarch Joint Venture explains the fall migration well here.
We are in luck! Throughout the spring, our local plant nurseries and retailers are selling several species of milkweed that is native to our area. The Asheville GreenWorks Bee City USA recommended species list provides a list of pollinator-safe native plants suppliers. The Montreat Native Plant Sale is April 23rd and the Botanical Garden of Asheville is having its spring plant sale on April 29-30.
Milkweeds are a perfect example of the importance of choosing the right plant for the right place. If you have a sunny and especially dry location, butterfly weed (Asclepias tuberosa) grows a long taproot and is quite drought tolerant once established. If you have a sunny but soggy spot, swamp milkweed (Asclepias incarnata) is tolerant of having “wet feet.” If you have a sunny area with soil of moderate moisture, take your pick! If you have a larger sunny area, you may want to plant common milkweed (Asclepias syriaca). This species spreads by horizontal underground rhizomes. Be prepared for it to move around and also form large colonies in a short amount of time. For this reason, it is typically recommended for more naturalized plantings or pocket meadows instead of smaller or more formal gardens. If you have a shadier site, poke milkweed (Asclepias exaltata) will not only survive, but thrive and even bloom in partial shade. If your milkweed gets tall and leggy, consider trimming it back in early July to regrow in time for monarchs’ fall migration.
There are two nonnative/tropical (annual) species generally available to gardeners, Mexican Milkweed (Asclepias curassavica) and Balloon Milkweed (Gomphocarpus physocarpus, formerly known as Asclepias physocarpa). Though widely available, attractive, long-blooming, fast-growing, and easily propagated, it is best not to plant these non-natives in WNC for several reasons. In warmer regions where they don’t die back in winter, a build-up of a debilitating protozoan parasite (Ophryocystis elektroscirrha or OE) that infects monarchs can occur. While tropical milkweeds should eventually die back during western North Carolina winters, another concern is their presence in fall could cause migrating monarchs to break diapause (a temporary non-reproductive state) and lay eggs instead of completing their migration to Mexico. Reseeding is also a concern.
When you plant, mark your milkweed! Milkweed is notorious for emerging in late spring (usually late April), just when you plant over it because you’ve given up. Leaving its stems and labeling the spot will remind you to be patient.