Milkweed

Some PEI plants are revered while others are reviled, but today’s plant is both. Meet Common Milkweed (Asclepias syriaca).

Our Island has two species of Milkweeds: the native Swamp Milkweed (Asclepias incarnata) and non-native Common Milkweed, shown here. Common Milkweed is native on the mainland. PEI’s earliest local records were along the rail line – thanks to seeds hitchhiking on trains – and that’s still where I most commonly see this species.

The mixed public opinion about Milkweed is all a result of how this plant defends itself against predators. Milkweed has a white, sticky sap that contains bitter-tasting toxic chemicals called cardenolides (cardiac glycosides). The stickiness gums up most insect predators while the bitter toxins deter both insects and mammals. But nature is a continual arms race, and some insects have found ways to evade – or even use – Milkweed’s defences.

While various species of aphids, beetles, bugs, and caterpillars feed on Milkweed leaves, sap, and seeds, the endangered Monarch Butterfly is the most famous. Unlike the others, Monarchs must have Milkweed to complete their life cycle: no Milkweed, no Monarchs. It’s for this reason that Milkweed is often revered.

On the other hand, Milkweed has traditionally been reviled in agricultural landscapes and is listed as a noxious weed in some areas (including Nova Scotia and Manitoba). It can invade pastures and hayfields, and has been the cause of poisoning in cattle, sheep, horses, and poultry. The historically-negative view of Milkweed is easing as appreciation of its importance to wildlife grows.

Milkweed’s sweet-smelling flowers (top right photo) offer nectar for a range of pollinators including bees, butterflies, flies, moths, and wasps. Some of the insects that arrive for a meal will slip a leg into an opening that contains the sticky pollen. Only the largest can successfully extract their pollen-covered appendage, and if you look closely at a cluster of Milkweed flowers, you may find trapped insects (or legs they left behind!). This by-catch isn’t unique to Common Milkweed but is a trait shared by many Asclepias species as well as some other Family members, such as Spreading Dogbane (Apocynum androsaemifolium).

In late summer, Milkweed’s flowers develop into distinctive seed pods (bottom right photo) that will open to release seeds attached to white fluff in fall. Called floss, that fluff helps Milkweed seeds disperse in the wind, and has traits that make it useful to humans: it’s soft, warm, lightweight, buoyant, and water-resistant.

While it’s not well-suited to spinning, Milkweed floss has been used for stuffing everything from pillows to life-jackets (during World War II, more than one million life-jackets – aka ‘Mae Wests’ – were made from Milkweed). The fibres also absorb oil and have been used in Canadian-made oil spill cleanup kits.

Despite its toxic reputation, Milkweed also has edible and medicinal uses. The sap has been used to treat cuts and burns, and ease the effects of Poison Ivy. Cardenolides are detoxified with heat, and all parts of Milkweed can be cooked and eaten at various times of year. Young shoots can be harvested in spring and unripe (green) flower buds in summer, and both can be blanched or steamed as a vegetable. Flowers can be used to infuse syrup or vinegar, and young pods can be blanched, steamed, or fried.

Our native Swamp Milkweed is rare on PEI, so if you’re looking to forage this plant stick to the non-native Common Milkweed, shown here. The Macphail Woods Nursery in Orwell sells Swamp Milkweed, and many people are using it to enhance their own parts of PEI Untamed!