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 - Greenish white, about 1/4 in. across, on short pedicels, in dense clusters at ends of branches and from the axils. Calyx of 5 segments; corolla nearly erect, bell-shaped, 5-lobed, with 5 small triangular appendages alternating with the stamens within its tube. Stem: 1 to 4 ft. high, branching, smooth, often dull reddish, from a deep, vertical root. Leaves: Opposite, entire, 2 to 6 in. long, mostly oblong, abruptly pointed, variable. Fruit: A pair of slender pods, the numerous seeds tipped with tufts of hairs.
Preferred Habitat - Gravelly soil, banks of streams, low fields.
Flowering Season - June - August.
Distribution - Almost throughout the United States and British Possessions.
Instead of setting a trap to catch flies and hold them by the tongue in a vise-like grip until death alone releases them, as its heartless sister the spreading dogbane does (see p. 134), this awkward, rank herb lifts clusters of smaller, less conspicuous, but innocent, flowers, with nectar secreted in rather shallow receptacles, that even short-tongued insects may feast without harm. Honey and mining bees, among others; wasps and flies in variety, and great numbers of the spangled fritillary (Argynnis cybele) and the banded hair-streak (Thecla calanus) among the butterfly tribe; destructive bugs and beetles attracted by the white color, a faint odor, and liberal entertainment, may be seen about the clusters. Many visitors are useless pilferers, no doubt; but certainly the bees which depart with pollen masses cemented to their lips or tongues, to leave them in the stigmatic cavities of the next blossoms their heads enter, pay a fair price for all they get.
From the fact that Indians used to substitute this very common plant's tough fibre for hemp in making theirfishnets, mats, baskets, and clothing, came its popular name; and from their use of the juices to poison mangy old dogs about their camps, its scientific one.