How to Find Locally Sourced, Native Milkweeds for Your Monarch Butterfly Habitat

How to Find Native Milkweeds for Your Butterfly Garden

Locally sourced, native milkweeds are vital to monarch conservation.
Locally sourced, native milkweeds are vital to monarch conservation. Flickr user Joseph Enos (CC by SA license)

The recent news about the decline of the North American monarch butterfly population has many people worried that this much beloved butterfly might disappear. We probably don't need to worry about the monarch butterfly's extinction just yet, but the remarkable phenomenon of the monarch migration is very much in peril in North America. Habitat loss along the monarch migration route is a major contributing factor in this decline.

Fortunately, there is something everyone can do to help save the monarch migration – plant milkweed.

Why You Should Plant Locally Sourced, Native Milkweeds

Monarch researchers recommend planting locally sourced, native milkweed species to provide the best habitat for monarch caterpillars in your area. As you probably know, monarch caterpillars feed on milkweed, which contains toxins called cardenolides that provide them with some protection from vertebrate predators. Cardenolides are steroids that affect the heart (cardiac glycosides) and are thought to make the monarch unpalatable to birds, mice, and other predators.

These cardenolides remain in the monarch's system through pupation and into adulthood, although research shows the concentration of cardenolides in a monarch's body decreases with age. A 1989 study by S. B. Malcolm and Lincoln Brower showed that cardenolide concentrations vary between milkweed species, and also vary quite a bit between individual plants within an Asclepias species.

Because we still have much to learn about the interactions between milkweeds and monarchs, it's probably best to stick with restoring monarch habitat by using milkweeds native to the region, and propagated from local milkweed stock. Dr. Karen Oberhauser, a leading monarch expert from the University of Minnesota, notes that planting non-native tropical milkweeds in southern areas may lead to an increase in Ophryocystis elektroscirrha (OE) infection rates, as monarchs breed continuously on the same milkweed stock.

The availability of milkweeds beyond the normal growing season could also impact the behavior of migrating monarchs.

Where to Find Local, Native Milkweeds for Your Butterfly Habitat

First, determine which milkweed species are best for your region. There are several good resources to help you find the right Asclepias species for your butterfly habitat:

The Monarch Joint Venture provides a fact sheet called Plant Milkweed for Monarchs, detailing the best milkweed species for each of 6 U.S. regions – Northeast, South Central, Southeast, Western, California, and Arizona.

The Xerces Society also offers regional fact sheets to help you choose appropriate milkweed species. You can download PDF fact sheets for the Great Basin region, the Central U.S., and California on their Project Milkweed website.

The Biota of North American Program website provides detailed range maps for each Asclepias species.

If you plan to propagate milkweed from seed:

Collect seeds from local milkweed plants when seed pods turn brown and break open. You can direct sow milkweed seeds in the fall. If you prefer to plant in the spring, store the seeds in an envelope in your refrigerator for the winter, or at least in a cool, dry location.

You can start milkweed seeds indoors, 6-8 weeks before you plan to transplant the milkweed to your butterfly habitat. Most temperate milkweed species will require seed stratification, and some species may also require scarification.

If you can't find plants locally to harvest seeds, you can purchase milkweed seeds from a vendor. Use the Xerces Society's Milkweed Seed Finder, a directory of milkweed seed vendors, to find a supplier that sells native milkweeds for your area. Just be sure to ask the vendor where the seed was sourced, and request seed collected from stock in your region whenever possible.

If you plan to plant milkweed plants:

One of the easiest (and cheapest) ways to obtain milkweed plants for a new butterfly habitat is to transplant milkweed from another location nearby. Milkweed is, after all, a weed, right?

Native milkweeds often grow and spread vigorously along roadsides, in vacant lots, and in meadows and fields. Of course, it's important to get permission before removing plants from property you don't own, but most landowners with an abundance of milkweed will be more than happy to let you take a few plants. Milkweed can be a little cranky when transplanted, so expect some drooping and water the plants in well when you plant. They should bounce back within a week or so, if given proper care.

If you can't find milkweed growing locally to transplant, you may be able to purchase milkweed plants at a native plant nursery in your area. Just be aware that nursery stock may not originate from your region, even if it's a species native to your area. Ask your local nursery owner where the milkweed came from, and choose plants sourced nearby whenever possible.

Finally, you can order milkweed plugs from Monarch Watch's Milkweed Market. The Milkweed Market propagates and overwinters plants from the seeds of native milkweeds around the country, and will only ship you plants that were grown from seed sourced in your region. You can help the Milkweed Market meet their mission of milkweed restoration by collecting and contributing milkweed seeds from your area.