Thursday, July 2, 2009

LOOK FOR: Common Milkweed

Milkweed is a beautiful, once-common roadside plant that is struggling in modern times. If you love monarch butterflies, you should show milkweed some love. Their lives depend on it: monarch larvae can only survive by eating milkweed leaves.


Photo credit: The Natural Capital
In June, common milkweed starts to form clusters of green balls -- the flower buds. And later in the month, these buds burst open into showy balls of tubular pink flowers. At 3-6 feet tall, with multiple flower clusters per stalk, this can be a very showy plant. On the few occasions I've come across a really large field of common milkweed, I've been intoxicated by the fragrance and the multitudes of pollinators dancing about. It's a lovely way to spend an afternoon.


Photo credit: The Natural Capital
There are many species of milkweed in the genus Asclepias. All share the property that when you break a leaf or stem of the plant, a white latex oozes out. (A 3-year-old friend recently tried to explain to me how cows get this "milk" into the milkweed, but I didn't quite follow it all.) Common milkweed, Asclepias syriaca, apparently got its scientific name through a botanical mix-up in the 1600's with a plant from the middle east (thus the Syrian epithet). Actually, this plant is all-American, and widespread east of the Rockies.

But not as widespread as it once was. Development and roadside mowing have dramatically reduced the milkweed available for hungry monarch caterpillars. Though logging in the monarchs' Mexican wintering grounds gets more attention, they also have less and less habitat for raising young here in the north every summer. Some states have started to catch on that by mowing roadsides just once or twice a year in spring and fall, they can save money and help wildlife at the same time. Let's hope this trend spreads.


Photo credit: ocean of stars
In addition to supporting monarchs and many other pollinators, common milkweed was a staple plant for many Native Americans. At this time of year, the flower buds (pictured to the right) can be cooked much like broccoli. However, if you are going to eat milkweed, it is important to learn to distinguish it from poisonous dogbane (Apocynum cannabinum, aka indian hemp), which can look similar (same height, milky sap but less of it, similar shaped leaves but smaller). Dogbane has different flowers and no fuzz on the stem or undersides of the leaves as milkweed has. The most important difference is that dogbane is very bitter, while milkweed should taste like a sweet green vegetable. It really is quite good.

In the wild: Milkweed likes the sun -- look around unmowed open fields, power line clearcuts, and roadsides. For those of you around Takoma Park, there's quite a bit growing downhill from the track at Takoma Middle School, making a valiant stand against the invasive kudzu and porcelain berry.

In your yard: Common milkweed isn't recommended for yards because it can spread quite aggressively by underground roots. If you have an area like a street box that is self-contained it might work well there. Otherwise, try a less aggressive species, like swamp milkweed (Ascelpias incarnata) or butterflyweed (Asclepias tuberosa). Monarch larvae can survive on any species of Asclepias, and we've found them on both of these in our yard. Both are beautiful -- and likely to be the subject of future posts!