Milkweed for Monarch Butterflies

Have you been watching a nice patch of milkweed along a public road, only to have it cut down in June by the local road commission? It happens every year near where I live. While cutting the milkweed can be beneficial for Monarchs, they always cut it at the worst possible time. Usually, this large-scale mowing happens when the first new brood of larvae for the summer are nearing their final instar, thus destroying a whole generation. On a smaller scale such as your garden, cutting of some milkweed plants can be beneficial. When you cut off the milkweed early enough in the season, it will regrow with nice tender succulent leaves that are perfect for young larvae to consume. The milkweeds in the accompanying photo were cut with the usual brush hog down to about 3 or 4 inches. It is recommended in the garden to only remove two thirds of the plant when cutting back to encourage new growth. By not cutting all the plants you have, you will be allowing some to bloom, providing nectar for many insects and especially for the Monarch butterflies. The uncut plants will also produce seed to continue propagating more plants in the coming years. Don’t cut to late in the summer, as having young tender leaves could trigger females to develop sexually and contribute to late egg laying rather than preparing to migrate. Aging milkweed is one of the triggers leading to the fall migration, other fall triggers are: length of daylight, decreasing temperatures and lessening nectar sources. Also, by allowing milkweeds to bloom late in the season, could affect the migration due to unusually late nectar sources.

With Michigan having 11 species of native milkweeds, which ones should you plant? First of all, plant only those native to your area. Planting non-natives such as Tropical milkweed (Asclepias curassavica) can cause problems for Monarchs. There are reports of Monarchs continuing to lay eggs through the winter and not migrating where Tropical milkweed can be grown year around in the south. It is also good to source your seed or plants as close to where you will be growing them. While any milkweed species is a possible larval host, some seem to be more widely used than outers. Common milkweed (Asclepias syriaca) and Swamp milkweed (Asclepias incarnata) seem to be favorites here in Michigan with the orange Butterfly-weed (Asclepias tuberosa) coming in third in my many years of observations. I have only seen larvae on other species a few times over the years. Keep in mind that Common milkweed moves and may come up anywhere near where you planted it. I have two stands in my yard that I didn’t plant. Most importantly, make sure it is native and of a local source.

With all the push for planting milkweed for the Monarchs, let’s not overlook the need for other native plants as nectar sources. Monarchs use many other plants besides milkweed to feed on the nectar. Provide native plants that bloom throughout the season with different plants blooming at different times from late May into later September. Liatris, milkweeds, Goldenrods, Mountain mints, many composites including Rudbeckias, asters, and Silphiums work really well to attract many species of butterflies including Monarchs. The last generation of Monarchs in the fall need these plants to build fat to fuel the coming migration and those migrating need to re-fuel along the way.

Feed the larvae and adult butterflies and enjoy watching them in your garden!

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