The common milkweed (Asclepias syriaca) has a knack for falling into and out of favor, depending on which way the wind blows its tufted seed. Naturalists and butterfly gardeners sing the milky-sapped weed's praises because it's the food source for the monarch butterfly's larva. During the Second World War, Japan controlled the silk-cotton tree's (Ceiba pentandra) principal growing regions ... the fibers (kapok) obtained from this tree were used to stuff life preservers. Since milkweed also produces a hollow, wax-coated, flexible fiber it was considered to be an excellent substitute for kapok. A pound of milkweed floss could keep 100 pounds of sailor afloat for about 10 hours. So valuable was the milkweed floss that there was a national drive to collect milkweed pods at centralized processing centers ... by some estimates, more than 25 million pounds of pods were collected and processed in 1944 and 1945. Milkweed is still grown and its fiber is used to stuff pillows and for insulation in clothing.
Shortly after the war, the tap-rooted milkweed became the bane of many a farmer's existence. Although the weed doesn't generally appear on any noxious weed lists, it can be problematic with some kinds of row crop cultivation. It seems funny how a native plant species can become a weed ... it all depends on your point of view.
Today, common milkweed is about to be born again. It seems that this hardy plant's seeds are full of unsaturated oils that according to researchers at the ARS National Center for Agricultural Utilization Research can be used as a base material for sunscreen, cosmetics and skin- and hair-care products, including moisturizers and conditioners. Getting the oils to be effective UV absorbers requires zinc chloride catalysis of the milkweed oil's triglycerides into cinamic acid drivatives.
In tests at the center's New Crops and Processing Technology Research Unit, the cinamic acid derivatives absorbed UV light with skin-damaging wavelengths from 260 to 360 nanometers -- and they worked at concentrations far below those approved for chemical additives and fillers used in today's sun blockers.
But that's not all. Common milkweed oil might be useful for other industrial applications such as paint and epoxy manufacturing.
I am excited to see common milkweed once again in the limelight as more than a butterfly food and lovely wild flower. I am not excited by the prospect of some large chemical company trying to genetically engineer this well adapted wild plant to produce more oil. However, the entire story begs the question of when a weed is really a weed.
Photo: iStock; Tim Messick
Hank Will raises hair sheep, heritage cattle and many varieties of open-pollinated corn with his wife, Karen, on their rural Osage County, Kansas farm. His home life is a perfect complement to his professional life as editor in chief at GRIT and Capper's Farmer magazines. Connect with him on Google+.