Growing Milkweed for Resurgent Monarchs

After the emergence of genetically engineered crops over twenty years ago all but wiped out their primary food source, milkweed, the Pacific Northwest’s migratory monarch butterfly population dropped roughly 90 percent. Sightings of the orange and black butterflies, which used to pass through the region on their way to California in the tens of thousands, have been rare in the last few years.


Recently, monarchs have been making something of a comeback in Oregon, but they could use all the help they can get. Perhaps the best way to assist the monarch resurgence is to plant milkweed. Here’s how you can help:

Finding Milkweed

The first step is, obviously, finding milkweed to plant. The Xerces Society, a nonprofit organization dedicated to wildlife protection, offers a milkweed seed finder that lists suppliers of native, regional plants. According to Sarina Jepsen, endangered species program director for Xerces, the more local the milkweed, the better. “Plants adapt to varying conditions over time,” Jepsen said, “and we’re trying to mimic the historic composition of milkweed and the landscape.

Jepsen added, however, that local and native milkweeds are more important if they are to be planted in the wild. If you’re planting them in your garden, non-native species are a-okay. The only variety to watch out for is tropical milkweed. Typically found in the southern US, this strain doesn’t “hibernate” over the winter, which can leave monarchs breeding and feeding on the plants when they should be migrating south to Mexico for the winter.

Tending Milkweed

Once you’ve secured your milkweed plants, you need to care for them properly. Because they require a stretch of cold and wet conditions to germinate, milkweed seeds should ideally be planted in the fall or winter. However, according to retired US Forest Service nursery specialist Tom Landis, if you want plant seeds in the summer, you can wrap them in a damp towel and refrigerate them for a few weeks first. More mature plants in bulb form can be planted practically any time.

Full sun exposure and open space is key. Water is important as well, of course. Milkweed is a sturdy enough plant that the soil type doesn’t much matter. Once they’re growing, they’re good to go, Landis said. “A lot of native plants, once they’re established, they really don’t require much care at all.”

Milkweed is generally not affected by pests. The only ones to watch out for are oleander aphids, which can be easily dealt with by simply hosing down the milkweed to wash them away. Planting onions or marigolds, natural pest repellents, is also highly effective. Definitely do not use pesticides.

Finally, keep in mind that it may be a few years before your milkweed plants are large and mature enough to attract monarchs.

Photo credit: gapowell / Foter / CC BY-NC-SA