There are over 2,000 species of milkweed in the world. 108-110 milkweed species are native to North America. ONLY 27 of these are used by Monarchs as host plants.
Those of us wishing to create Monarch Waystations full of nectar and caterpillar plants need to do our homework to learn which native milkweeds Monarchs will lay their eggs on. Planting species native to your region is key.
Native Milkweeds Region-by-Region
Monarch Joint Venture has done the homework for us; their milkweed information sheet presents the best native milkweeds region-by-region (Northeast, Southeast, South Central, Western, California, and Arizona). They also provide a directory of native plant vendors that sell milkweed plants and/or seeds.
If you want more exact information about where each native milkweed grows, visit the Biota of North America Program’s North American Plant Atlas Asclepias page for distribution maps for each milkweed species across the continent. The distribution maps in the USDA’s plants database for Asclepias (Milkweed) are also very helpful (click on the “SUBORDINATE TAXA” link to see all maps).
Teammate Carole Brown in her post “can milkweed be bad for Monarchs” took a close look at some of the reasons non-native milkweeds should be avoided. This followed Kathy Villim’s post at Beautiful Wildlife Garden about her visit to a Monarch Butterfly wintering site in California where docents had been advised by experts to remove milkweed that had been planted at this overwintering site because it was disrupting the migratory cycle.
Living at Cape May, a Monarch migration hotspot, I wanted to throw in my two cents. Not only do we see some terrific concentrations in the fall, but Cape May wildlife gardens are nurseries for generation after generation of Monarch spring through fall. As an environmental educator Monarch Lab has answered so many of my questions about Monarchs and milkweeds.
Cape May Has a Mix of Populations in the Fall
- migrants from the north that are passing through (in sexual diapause, no longer interested in breeding, but instead entirely focused on migrating)
- locals that are enjoying Cape May’s microhabitat (buffered by the warm waters of the Atlantic Ocean to the east and the Delaware Bay to the west) and continuing to breed, lay eggs, create the next generation, and die. We’ve found eggs from these locals as late as early November. It’s a lottery, of course, since it will take at least one month for the life cycle (egg to adult). If a freeze occurs these late eggs, caterpillars, chrysalises, and adults might not survive. But if no freeze occurs, the population has grown by one more generation.
Tropical Milkweed, an Annual
I’ve planted all the milkweeds native to South Jersey in my garden. Some have flourished (Common Milkweed and Swamp Milkweed). A few have limped along (Butterfly Weed – my soil is just too good, not barren enough). Some have come and gone (Poke Milkweed, Whorled Milkweed), unhappy in my garden.
As a wildlife gardener I compliment my native plant garden with annuals. They’re easy to grow, forgiving when nature scorches or saturates the soil, they’re non-stop bloomers, and they readily regenerate when nibbled. Tropical Milkweed is just such an annual that I save room for in my garden each year.
Tropical Milkweed is an amazing Monarch caterpillar plant. I’ve seen it eaten to the bone (with only the stems remaining) and watched in awe as it regenerates new leaves, buds, and flowers like the Energizer Bunny. I’ve watched individual plants regenerate multiple times over the course of the summer and fall.
Some years there are so many eggs and caterpillars on my Tropical Milkweed that it barely has a chance to regenerate. I’ve stepped in and moved hundreds of caterpillars to my stands of robust Common Milkweed plants to give the Tropical Milkweed plants a chance.
Tropical Milkweed does not survive the winter in my garden. I would probably reconsider and steer clear of it if that was the case. With global warming I may yet need to take that stand. But for now, Tropical Milkweed has a place in my garden and offers nectar to so many different butterflies for many months and serves as an excellent caterpillar plant for hundreds upon hundreds of Monarchs.
Monarch Watch shares that gardeners living where Tropical Milkweed survives the winter have taken to cutting it back to the ground from time to time so that new growth regenerates and hopefully lessens the possibility of the protozoan, Ophryocystis elektroscirrha (O.e.), surviving on the plant.
Never Enough Milkweed
Too many roadside stands of milkweed are mowed down. In my mind, the responsible gardener can’t offer enough milkweed in their habitat. The more patches of milkweed scattered hither and yon, the better the chances of Monarch eggs, caterpillars, chrysalises, and adults surviving predators.
Pat Sutton, of Cape May NJ, is an author, educator, and naturalist who has taught gardening for wildlife workshops and led tours of private wildlife gardens for over 30 years. She shares her passion around the country at festivals and conferences and is available to speak to your group or organization.
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