September 25, 2012
Milkweed fruits: Pods of plenty
As September winds down, milkweed pods dry out and split open, releasing flat, brown seeds carried aloft by a white, silky fuzz known as milkweed floss.
The hollow fibers are coated in wax, making them waterproof and buoyant, a quality exploited during World War II after the Japanese occupation of Java cut off supplies of kapok, a fluffy plant fiber used in life vests. (Today's vests use synthetic fibers.)
To fill the gap, defense contractor War Hemp Industries enlisted American schoolchildren to scour the September landscape for ripe milkweed pods, paying kids 15 cents to fill an onion bag with pods. Each open-mesh bag held about a bushel, or 600 to 800 pods. Two bags provided enough floss for one life vest. More than 1.5 billion pods were collected to make 1.2 million life vests.
Francis Joey Wilson Jr., who was 10 years old in 1944, remembers his father tipping him off about a poster promoting the pod harvest near their home in Upper Marlboro. "All my friends jumped on our bikes and took off for the post office to read the notice for ourselves," writes Wilson. Later, his bags full of pods were collected behind the post office and hauled away by a big truck. "They were paying about 5 cents a pound," says Wilson.
These days, milkweed pods are worth about 55 cents a pound, and they are still collected by people toting onion bags through the North American countryside. The floss is harvested to help fill pillows, comforters and stuff into jackets.
Milkweed floss is best used in combination with goose down. Floss by itself clumps together after being washed, but when mixed with down, floss smoothes out the texture of down without compromising down's other qualities. Floss is about half as costly to produce as down.
Milkweed pods provide more than just fibers: Their seeds yield an omega-7-rich oil. The Nebraska company Natural Fibers extracts the oil for a balm it sells as an anti-inflammatory. Although the FDA has not evaluated the balm's claimed benefits, the agency did reject a proposal by Natural Fibers in 2009 to recognize milkweed-seed oil as a new dietary ingredient, noting the presence of toxins in milkweed and questioning the safety of a proposed use of organic solvents to extract the oil.
Herb Knudsen, president of Natural Fibers, says the balm isn't extracted with organic solvents. "We cold-press the oil," mashing 200 pounds of seeds an hour in a seed press at room temperature.
Knudsen, 71, former vice president of new ventures at Standard Oil of Ohio, acquired the energy company's experimental "Milkweed Project" in 1987, making it his own. He downplays presumed toxins in milkweed-seed oil: "Their amounts are at such low levels that they do not harm anyone," but proving that to the FDA would be prohibitively expensive.
"Topical applications do not need FDA approval," says Knudsen, who rubs milkweed balm into his osteoarthritic hip that was due for replacement. "But the benefits of the oil have kicked that can down the road for now."
Sources: The Erie County Independent, Toxicological Sciences, New Crops, University of Nebraska
October 2, 2012
Although the fat, exotic mollusk is abundant in the shallow bays of the Potomac River, what's known about it is slim. Among its many mysteries is how the two-inch-long snail affects native aquatic life.
Michelle Ryan, a George Mason University doctoral student, is a gumshoe in a kayak, tracking mystery snails in the river. Funded in part by the Occoquan Watertrail League, Ryan and the volunteers whom she trains nab snails from Occoquan and Belmont bays, measuring shells, pinpointing locations and cataloguing water and weather conditions. "I am focused on why they are here, what niche they are playing in the environment and whether they are adding to or subtracting from our freshwater system," she says.
Her surveillance of the scientific literature reveals a few intriguing facts:
■ The snails are gluttons for algae growing on the river's bottom, yet they excrete very little of the pollutants phosphorus and ammonium.
■ In their tissue, the snails concentrate spilled oil and other toxins, a trait that makes them potentially valuable as tipsters on pollution.
■ They can close their shell and survive out of the water for as long as a month.
■ When water temperatures rise above 59 degrees, a female snail starts birthing quarter-inch-long juvenile snails — a hundred at a time. If pressured by predators, she can reproduce at twice the normal rate. Females live for about five years, males for three. They retreat to deep waters for the winter, where they hibernate in the mud.
■ Merchants and sailors brought mystery snails to the West Coast in the 1890s for Asian food markets. By 1911, the snails had escaped to California irrigation ditches. Demands by food, aquarium and water-garden markets helped spirit the snail across the country. By 1960, mystery snails had found a haven in the Potomac at Alexandria.
■ The snails are native to East Asian rice paddies, where they are snatched up for the dinner table. They're capable of transmitting parasitic flatworms, but no human infections have been recorded.
■ Pet stores sometimes sell brightly colored apple snails under the name "mystery snail," but the real deal is olive to dark brown, sometimes using the alias "trapdoor snail." To scientists, the true identity of mystery snails is elusive. Maybe they are Chinese mystery snails, which are a bit squatter in profile, or perhaps they're Japanese mystery snails, which tend to have more angular spires on their shells — or the two species might really be only one species that varies in shape. It's a mystery for now.
And how did that particular gastropod get the nickname "mystery snail"?
"That I don't know," confesses Ryan.
October 9, 2012
The fall of a champion tree
Cemeteries and parks often harbor giants, planted centuries ago as living memorials, now grown into monumental champion trees. The Washington area hosts several state champions and national champions. Even co-champions live nearby.
In a tie for the national title of biggest American holly are a tag team of trees from both sides of the Potomac, one at the Chelsea House historic site in Prince George's County and another in Christ Church Cemetery, adjacent to Alexandria National Cemetery. The Alexandria tree stretches 68 feet into the heavens. Arborists are uncertain of the tree's age, but tombstones surrounding the tree date to the early 1800s.
Titles are awarded based on a point system derived from tree dimensions (see graphic). Even bantamweight species can earn a spot on the podium: At South Payne and Gibbon streets in Alexandria, along the perimeter of the Wilkes Street Cemetery Complex, is the national champ dwarf hackberry, living large at 41 feet tall.
The District sports its own winning big tree, a nonnative fruit tree from Asia. On the Capitol grounds is the U.S. champion common jujube, 93 inches in circumference, 61 feet tall.
Not all big trees reside on public land. When champions occupy private property, however, things can get complicated.
In 2004, the nation's second-largest sweet gum, Virginia's state champ, stood in the way of a planned office development near Merrifield. After Fairfax County urban foresters recommended preserving the tree, an arborist hired by the developer argued that the triple-trunked tree was "at high critical risk for major limb or trunk failure," according to zoning case records. The arborist warned of "many targets, both people and property."
Urban foresters disagreed, saying that pruning and installation of a cable support system would "reduce the potential failure risk to an acceptable level." However, to survive, the tree would require an undisturbed 50-foot radius around its trunk to accommodate the roots.
Unacceptable, said the developer: "Ten surface parking spaces and 15 garage parking spaces will have to be sacrificed to preserve the sweet gum."
Zoning officials agreed. By 2008, the tree was gone, replaced by three young beech trees and a large parking lot, which sat mostly empty on a recent weekday afternoon, with more than 100 parking spaces available.
"I am not happy about the removal of a very large and old sweet gum," says Michael P. Knapp, Fairfax County's urban forestry director, "but I am satisfied that a bona fide effort was made" to preserve the tree.
The county "arguably has the strongest local tree conservation ordinance" in Virginia, Knapp says. Adopted in 2009, the law requires planners to identify champion trees and to make attempts to protect them.
Think you might know of an unheralded champion? Check the links below:
The District champions
Big tree scores are tallied from three measurements: Height, trunk circumference at chest height (4.5 feet) and a quarter of the average crown spread. A shorter, fatter tree can share the title with a thinner, taller tree of the same species.
If the numbers are close, arborists call it a tie.