Latin for Gardeners
August’s Native Maryland Plant
Asclepias syriaca L.
(as-KLEE-pee-as seer-ee-AY-kah)
Common Name: Common Milkweed
After reading Barbara Kingsolver’s novel, Flight Behavior last month – I can’t get the plight of monarch butterflies out of my mind; I thought it high time to feature a common plant in the genus Asclepias – one that monarchs simply can’t live without.
Tall, fragrant and robust, common milkweed is often found growing in sunny fields and along roadsides – thank goodness. Asclepias syriaca is just one of the critically important milkweed species used as a host for the monarch butterfly caterpillar. When in flower, its blooms provide many insects both nectar and pollen, but for the monarch caterpillar the plant provides much more than that - Asclepias is the only genus that will support the monarch as a caterpillar and guarantee its future survival.
Mid-August is when the last generation of eggs for the year are laid by the monarch, so it’s crucially important for the insect to locate milkweed during this time – even if it’s just along a busy road. It was along a highway that I found it also attracting traffic on a sizzling hot July afternoon. Who would have thought that a ‘weed’ could stop traffic? Well, that’s what happens when you plant Common Milkweed where people can marvel at its spectacular large blooms, teeming with life, without even leaving their cars.
A. syriaca is extremely valuable for many insects, it’s often used in restoration projects and in larger gardens where its tendency to spread is welcomed and appreciated. It’s able to spread quickly by rhizomes or by seeds, often to areas where it’s uninvited – one reason it’s not as frequently planted in home landscapes. Two other native Maryland milkweeds that are less aggressive are often preferred by gardeners: Butterflyweed (Asclepias tuberosa) and Swamp milkweed (Asclepias incarnata) – they will also attract and support the full lifecycle of a monarch, but they grow in different conditions which must be considered when planting them. NOTE: I’ve found numerous articles that suggest the monarch prefers Asclepias syriaca and Asclepias incarnata as a host plant – more monarch eggs are found on these species than other milkweeds.
After blooming and as fall approaches, it’s not uncommon to find milkweed aphids (introduced oleander aphids) or milkweed beetles on the plants – sometimes in large numbers. Their bright aposematic¹ coloring makes them easy to spot and is a warning to predators of their toxicity. These insects can be unsightly, but they generally don’t harm the plant or the monarch caterpillar and efforts to remove them will more often harm the pollinators that are visiting the plant. Interestingly, the aphids are asexual, they are born pregnant and can form large colonies amazingly fast.
As you prepare your next conservation landscaping project, consider how you can help conserve the monarch butterfly by adding Asclepias syriaca to your planting plan. Perhaps choose a highly visible sight so that others can share the joy and witness the amazing flight behavior of these incredible insects.
¹aposematic - the use of warning coloration to inform potential predators that an animal is poisonous, venomous, or otherwise dangerous.
NOTE: You can learn more and follow the monarch migration here: https://monarchjointventure.org/
Alison Milligan – MG/MN 2013
Watershed Steward Class 7/CBLP
aligmilligan@gmail.com