This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - White or greenish, on short pedicels, in several small terminal clusters. Calyx inferior; corolla deeply 5-parted, the oblong segments turned back; a 5-parted, erect crown of hooded nectaries between them and the stamens, each shorter than the incurved horn within. Stem: 1 to 2 1/2. ft. tall, simple or sparingly branched, hairy, leafy to summit, containing milky juice. Leaves: In upright groups, very narrow, almost threadlike, from 3 to 7 in each whorl. Fruit: 2 smooth, narrow, spindle-shaped, upright pods, the seeds attached to silky fluff; 1 pod usually abortive.
Preferred Habitat - Dry fields, hills, uplands.
Flowering Season - July - September.
Distribution - Maine and far westward, south to Florida and Mexico.
In describing the common milkweed (pp. 135-138), so many statements were made that apply quite as truly to this far daintier and more ethereal species, the reader is referred back to the pink and magenta section. Compared with some of its rank-growing, heavy relatives, how exquisite is this little denizen of the uplands, with its whorls of needle-like leaves set at intervals along a slender swaying stem! The entire plant, with its delicate foliage and greenish-white umbels of flowers, rather suggests a member of the carrot tribe; and much the same class of small-sized, short-tongued visitors come to seek its accessible nectar as we find about the parsnips, for example. When little bees alight - and these are the truest benefactors, however frequently larger bees, wasps, flies, and even the almost useless butterflies come around - their feet slip about within the low crown to find a secure lodging. As they rise to fly away after sucking, the pollen masses which have attached themselves to the hairs on the lower part of their legs are drawn out, to be transferred to other blossoms, perhaps to-day, perhaps not for a fortnight. Annoying as they may be, it is very rarely, indeed, that an insect can rid itself of the pollen masses carried from either orchids or milkweeds, except by the method Nature intended; and it is not until the long-suffering bee is outrageously loaded that he attains his greatest usefulness to milkweed blossoms. "Of ninety-two specimens bearing corpuscula of Asclepias verticillata," says Professor Robertson, "eighty-eight have them on hairs alone, and four on the hairs and claws." And again: "As far as the mere application of pollen to an insect is concerned, a flower with loose pollen has the advantage. But the advantage is on the side of Asclepias after the insect is loaded with it. It is only a general rule that insects keep to flowers of a particular species on their honey and pollen gathering expeditions. If a bee dusted with loose pollen visits flowers of another species, it will not long retain pollen in sufficient quantity to effectually fertilize flowers of the original species. On the other hand, if an insect returns at any time during the day, or even after a few days, to the species of Asclepias from which it got a load of pollinia, it may bring with it all or most of the pollinia which it has carried from the first plants visited. The firmness with which the pollinia keep their hold on the insect is one of the best adaptations for cross-fertilization."
Ants, the worst pilferers of nectar extant, find the hairy stem of the whorled milkweed, as well as its sticky juice, most discouraging, if not fatal, obstacles to climbing. How daintily the goldfinch picks at the milkweed pods and sets adrift the seeds attached to silky aeronautic fluff I