Monarch populations have plummeted over 80% in the last 15 years and today only a fraction of the population remains. This population decline is tied to overuse of herbicides and pesticides, climate change, urban and rural development, and loss of natural environments. Monarch species are reliant on milkweed plants throughout their lifecycle and one of the best ways you can ensure the survival of the monarch is by planting milkweed.
Every spring monarch butterflies make the trek from Mexico north and return south from their summer breeding grounds each fall. Its a journey of over 6,000 miles and spans 4-5 generations. Monarchs are reliant on milkweed throughout this journey. Did you know that monarch caterpillars and immature butterflies can ONLY eat milkweed? It provides all the nourishment the caterpillar needs to transform into a butterfly while its flowers also provide nectar to other butterflies, bees, and beneficial insects. That is why female monarchs lay their eggs on milkweed - it's a necessity!
CHOOSING THE RIGHT VARIETY OF MILKWEED
The Xerces Society recommends planting milkweed native to your area. Native varieties of milkweed in WNC include Asclepias tuberosa (butterfly milkweed), Asclepias incarnata (swamp milkweed), and Asclepias syriaca (common milkweed).
NOT ALL MILKWEED IS CREATED EQUAL
Tropical (annual in WNC) milkweed can be toxic to monarchs - if grown in a warm climate where it can winter over, it supports a harmful parasite, and if grown in hot areas like ours, the concentrations of cardenolide can be harmful to the caterpillars feeding on them (cardenolide is the chemical that turns the monarchs orange, and while they can tolerate some of it, tropical milkweed can produce toxic levels). Finally, tropical milkweed usually blooms later in the year than native species, and therefore may confuse monarchs and cause them to breed when they should be migrating. So please opt for native perennial milkweed when planting! Here is a great blog post from the Xerces Society with more info.
Also be sure to assess your growing environment to see which variety will grow best for you. Asclepias tuberosa (butterfly milkweed) is drought tolerant and likes good drainage, Asclepias incarnata (swamp milkweed), and Asclepias syriaca (common milkweed) like more moisture. Swamp milkweed in particular lives up to its name and thrives in wetland environments and wet clay soil. The Xerces society recommend one full sized milkweed for one caterpillar. If buying plants from us (mostly 6" size), we recommend 3-4 per caterpillar to ensure they have enough food!
Be sure to plant your milkweed in a location where it will receive full sun!
MILKWEED AND PESTS
It is essential to not treat pests such as aphids found on milkweed - not even organic safe options like Neem oil should be used. If monarch caterpillars eat milkweed that has been sprayed with Neem they will be killed. Anything stronger, such as systemic pesticides, are even more potentially fatal to the monarchs. Aphids may not be pretty, but they won't kill your milkweed, so just ignore them!
The Xerces Society has a wealth of information on supporting monarch populations, planting milkweed, and supporting other pollinators - check out their many articles!