Swallow-Wort, the Common, or Asclepias alba v. Vincetoxi-cum, L. a hardy exotic plant, which is a native of the south of France, Spain, and Italy. In a fresh state, the root of this vegetable possesses a strong smell, resembling that of valerian ; to which, however, it is inferior in its sudorific and diuretic properties.
The stalk of the Common Swallow-wort is fibrous, and has on the Continent been employed as a substitute for flax by mixing it with silk, M. De BIborczFalva, a creditable economist in Hungary, has lately produced a mixed cloth, which was remarkably fine, and cost him about 4s. the yard, English measure ; being from 50 to 00 inches wide.
There is another species of this exotic, namely, the Syrian Swal-low-wort, or Silk-plant (Asclepias Syriaca, L.) a native of North America, and especially of Virginia. Its strong stalks attain the height of seven feet: the pale purplish flowers appear in June or July ; emit an agreeable odour ; and are succeeded by large, thick, and rough capsules, the seeds of which are furnished with a long, glossy silk. In this respect, it forms one of the most valuable productions; and, as the experiments lately made in Silesia, fully evince that it may with equal advantage be raised in the more temperate climate of Britain, we strongly recommend its culture, which is generally successful in the most indifferent soils. It may be propagated either by the seeds or roots ; vegetating most luxuriantly in a loose, sandy, and rather damp, ground. The seed should be sown in the spring, and the young plants be transplaced into a well-ploughed and manured land, where they must be properly weeded in the succeeding summer, and hoed, after having attained the height of 3 feet. When the principal stem displays the flowers, all the collateral branches and leaves should be carefully removed. The fruit attains to maturity in August, or September ; and, as soon as the external rind becomes soft, yellow, and wrinkled, the seed capsule is to be cut off during dry weather, and allowed to burst spontaneously. The dry stalks are next to be separated by the knife, applied closely to the root; the decayed plants must be re-placed by the roots of others ; then thinly covered for the winter with long dung; and, in the succeeding spring, the surrounding earth should be loosened. Although BecH-steiN, who has furnished us with this account, does not mention the distance at which the plants ought to stand; yet their size appears to require considerable space, so that they may be, at the least, 12 inches apart, in every direction. The silk, obtained from the seed-capsules of the Syrian Swallow-wort, is not only useful for staffing pillows, spinning fine yarn, both by itself and mixed with cotton, animal wool, and cod-silk, or the loose filaments of the cocoons ; but it also affords a valuable material for manufacturing paper of a superior quality. Its stalks may be advantageously employed as substitutes for hemp. In Canada, a brown sugar is extracted, by evaporating the juice of its flowers ; and, in Germany, the young tops are eaten as asparagus: hence, the assertion of some naturalists is erroneous, that the milky juice of this plant is of a poisonous quality.