Milkweed

We were driving from Ottawa to Montreal on a late October (2013) Sunday when I noticed cottony looking plants along the highway. We pulled over and I collected a few stems with the dry, half open seed pots attached. I took their photographs when we reached home. What beautiful images I had! When I looked it up I found out that this was milkweed. Had I not first seen  it in its  dry state, I would not have noticed milkweed and learned about it. This was my first discovery of a native Canadian plant.

Commonly known as milkweed or silkweed, Asclepias syriaca is native to Southern Canada and much of the conterminous (having a common border-I learned a new word) U.S. east of the Rocky Mountains. Too bad the species name is Syriaca meaning ‘of Syria’ which it is not. Carl Linneaus or Carl von Linné, as he was known later, named it in the mid-1700s but he confused it with the milkweed from the Orient. In botany, a name first assigned is unchangeable, regardless of errors in derivation or spelling.

A. syriaca is in the milkweed subfamily Asclepiadoideae (formerly in the family Asclepiadace) of the family Apocynaceae. Asclepias comes from Asklepios, the Greek god of medicine, for the medicinal properties of the plant.

A. syriaca is a species of flowering perennial herb. It grows in sandy soils and other kinds of soils in sunny areas starting from a rhizome and reaches a height of 60 to 120 cm. It was one of the earliest North American species described in the French physician and botanist Jacques-Philippe Cornut’s (1606-1651) 1635 work Canadensium Plantarum Historia.

Milkweed flowers bloom from June to August. The fragrant, nectariferous-nectar producing flowers occur in compound cymes. The flowers have five petals and they are rose to purple in color. Individual flowers are about 1 cm in diameter.

compound cyme


The leaves are broad, elliptical and opposite. The large leaves have very short petioles (the stalk by which the leaf is attached to a stem) and velvety undersides.

The fruit are green pods or follicles which turn brown before bursting open to let out beautiful fluffy seeds like the ones that drew my attention.

In late summer and early fall the seed pods mature and dry out, they crack open and release many disc shaped brown seeds borne by the wind on a plume of white silky hairs. The seeds are neatly packed in overlapping rows. One name for the filament like hairs they are attached to is pappus. The name pappus derives from the Greek word pappos, Latin pappus, meaning ‘old man’.

The pappus function as a ‘parachute’ which enables the seed to be carried by the wind.


                                

The leaves of the milkweed are the only food source for the Monarch butterfly larvae (caterpillars). Milkweed flowers are a nectar source for many butterflies but especially the Monarchs. Without milkweed we would not have these beautiful butterflies.

 Photograph: Aydın Örstan, Monarch butterfly at Black Hill Regional Park, 20930 Lake Ridge Drive, Boyds, Maryland, USA
 
I am learning that milkweed is also an important nectar source for many species of insects such as the native bees, wasps, and other nectar-seeking insects. The plant is a food source for a variety of herbivorous insects, including numerous beetles and moths, specialized to feed on the plant despite its chemical defenses. Milkweeds are a shelter and hiding place for other species as well. Yellow Jacket wasps eat bees and flies which get trapped in the flowers, and crab spiders ambush tasty visitors. Milkweed Bugs, and Milkweed Leaf Beetles only eat milkweed, and could not survive without it.

Yet, the plant is on Ontario’s noxious weeds list. All parts of the milkweed plant produce white latex when broken. The sap has poisons in it, called cardiac glycosides. These are similar to digitalis or digoxin, common heart medications used in both human and veterinary medicine. Consumed in large quantities milkweed has poisoned livestock.

Some animals can eat the glycosides and not be harmed. The Monarch butterfly caterpillars eat the leaves of milkweed and store its toxic compounds, which makes them unpalatable to predators. Even after the caterpillars change into adult butterflies, they keep the glycosides in their body.

       

Jack Sanders, author of the book titled The Secrets of Wildflowers (2003) provides interesting information on milkweed. He also shares my feelings of joy and amazement. He writes: “Milkweeds are among the great toys of nature, known to almost any kid who grows up in the country.” He quotes naturalist F. Schuyler Mathew (1894): “The common milkweed needs no introduction. Its pretty pods are familiar to every child, who treasures them until the time comes when the place in which they are stowed away is one mass of bewildering, unmanageable fluff.”

I could easily be that child had I known milkweed seeds.

To give nature a hand, milkweeds can be propagated from seeds, cuttings, and, in some cases, from root divisions.