Gardening for Monarchs
- Tigertown Farm
- 5 days ago
- 2 min read
Monarch butterflies are facing some serious threats. Over the past 20 years,
their populations in the eastern United States have declined 80-90%, likely due to a combination of a decline in milkweed populations, mortality during migration, and climate change [1].
Monarch caterpillars require what's known as a host plant, which is a specific plant that an organism needs to survive. In this case, monarch butterflies will only lay their eggs on (and caterpillars will only eat) plants in the Asclepias genus, commonly known as Milkweeds. The larvae have evolved to eat and use toxic cardenolide compounds in the milkweeds as a defense against predators.
Supporting monarch populations means we need milkweed plants! But there are over 200 species of plants in the Asclepias genus-- do all of them serve the same function? Which are the best to plant for monarchs?
What milkweeds are native to the Upper Valley?
Did you know that we have 8 species of milkweed native to VT and NH [2]? The most common is Asclepias syriaca, aptly named Common Milkweed, which features some gorgeous, complex, lilac-colored flowers. Other species have flowers ranging from white to orange! Perhaps surprisingly, despite relying on them as caterpillars, adult monarchs are pretty poor pollinators of milkweeds, and pollination is primarily conducted by bees and wasps.
Native Milkweeds of the Upper Valley | ||
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Do Monarchs have Milkweed preferences?
Most of the research that we found was done in the Midwest, where they do have a few different species of milkweed, so the results should be taken with a grain of salt. However, it has been found that Asclepias incarnata and A. syriaca are the most preferred species for egg laying. A. syriaca is the most abundant milkweed species, so it is hypothesized that this species might be the most important for monarchs! Interestingly, egg laying preferences changed over the season- A. syriaca was more preferred during the beginning and A. incarnata was used more during the middle to end of the season. Additionally, although fewer total eggs were laid on the species A. sullivantii (a species that isn't native here) and A. tuberosa, the larval survival rates were higher on these plants [3].
So what's the best species to plant for monarchs? Well, as is often the case in ecology, it depends. The best thing to do is to have several species available in your yard so the monarchs can have their choice! Additionally, make sure you support the adult monarchs with native flowers. Once they emerge as butterflies, the adults switch to feeding only on nectar from flowers. They also require lots of energy for their fall migration so plant some native fall blooms to help them out- Cone flower (Echinacea spp.), Blazing Star (Liatris spp.) and Asters (Symptotrichum spp.) are a few favorites!
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