|Common Milkweed pods split open to release seeds -- © Dave Spier|
Ripe pods splitting open to release silky floss can mean only one thing -- the milkweed seeds are ripe and ready for dispersal on autumn winds. Milkweeds need almost no introduction. In fact, the Common Milkweed (Asclepias syriaca) is just that -- common and widespread in fields and roadsides. The genus name refers to Asclepius, the Greek god of healing, because of the plant's use in folk medicine, much of it derived from native American practices. A quick word of caution, though. Avoid the milky juice which contains toxic compounds including alkaloids, glycosides and cardenolides. Monarch butterflies are immune to the effects of these substances and use them to their advantage by laying their eggs on the plant. The caterpillars eat the leaves, ingest the toxic substances, and become noxious prey to would-be predators. Apparently the effects last into adulthood. One experience of getting sick is probably enough to ward off a bird from eating any more larvae or adults. (Given the date of this post, I'd say this is no longer an issue till next summer.)
The species name, syriaca, is a case of mistaken identity. When the plant arrived in Europe (before 1753) it was believed to have come from the Middle East. Actually this particular species is native to North America. Worldwide, there are 140 species of milkweeds. Once considered to be a family of plants, the group has been downgraded to the rank of subfamily in the dogbane family.
The Common Milkweed's sticky, white sap can be used to make a natural rubber. During World War II, when tree latex from Malaysia became unavailable, the government experimented with milkweeds. Commercial-scale production of rubber would have required the redesign of existing processing facilities, so the effort floundered. Eventually most natural rubber was replaced by synthetics made from petroleum.
Milkweed did come to the rescue of the life-preserver industry which had relied on kapok from Java. When that source was cut off in 1942, school children and scout troops in 26 states were paid 20 cents for each onion bag they filled with ripe milkweed pods (roughly 800 pods per bag). The flossy seed hairs are waxy on the outside and hollow on the inside (much like kapok). This makes them super-light and water resistant, which is perfect for life vests. Less than two pounds of filling could keep a sailor afloat on the sea for two days. After the war, milkweed again sank commercially because it was cheaper to import kapok. The only remnants of the war effort are the nicknames silkweed, Virginia silk, cottonweed and wild cotton.
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|Common Milkweed seeds travel on silky parachutes -- © Dave Spier|