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.
In dry, open woodlands, thickets, and roadsides, from August to October, we find the dainty White Wood Aster (A. divaricatus) - A. corymbosus of Gray - its brittle zig-zag stem two feet high or less, branching at the top, and repeatedly forked where loose clusters of flower-heads spread in a broad, rather flat corymb. Only a few white rays - usually from six to nine - surround the yellow disk, whose florets soon turn brown. Range from Canada southward to Tennessee.
White Wood Aster (Aster divaricatus)
First to bloom among the white species, beginning in July, is the Upland White Aster (A. ptarmicoides), which elects to grow in the rocky or dry soil of high ground in the northern United States westward to Colorado. The leaves, which resemble grayish-green shining grass-blades, arranged alternately up the rigid stem, and diminishing in size near the top until they become mere bracts among the flowers, enable us to name the plant. The heads, in a branching cluster, are not numerous; each measures barely an inch across its ten to twenty snow-white rays; the centre is of a pale yellow-green, turning a light brown in maturity.
The Tall White or Panicled Aster (A. paniculatus), in bloom from August to October in different parts of its wide range, attracts great numbers of beetles, which do it more harm than good; but many more butterflies (some of whose caterpillars feed on aster foliage as a staple), quantities of flies, some moths, swarms of bees, wasps, and miscellaneous winged visitors. Professor Robertson found several thousand callers, representing ninety-eight distinct species, on this one aster during four October days. Such popularity as the asters have attained finds its just reward in the triumphant progress of the lovely tribe (see page 73). For the amateur to name each member of such a horde is quite hopeless. In branching, raceme-like clusters, from August to October, this aster displays its numerous flower-heads, less than an inch across, each with a green cup formed of four or five series of overlapping bracts, and many white rays, occasionally violet tipped. The smooth stem, which rises from two to eight feet above moist soil, is plentifully set with alternate, pointed-tipped, lance-shaped leaves, tapering to a sessile or partly clasping base, and sparingly saw-edged. Its range is from Montana east to Virginia, south to Louisiana, north to Ontario and New England.
The bushy little White Heath Aster (A. ericoides) every one must know, possibly, as Michaelmas Daisy, Farewell Summer, White Rosemary, or Frostweed; for none is commoner in dry soil, throughout the eastern United States at least. Its smooth, much branched stem rarely reaches three feet in height, usually it is not over a foot tall, and its very numerous flower-heads, white or pink tinged, barely half an inch across, appear in such profusion from September even to December as to transform it into a feathery mass of bloom.
Growing like branching wands of golden rod, the Dense-flowered, White-wreathed, or Starry Aster (A. midtiflorus) bears its minute flower-heads crowded close along the branches, where many small, stiff leaves, like miniature pine needles, follow them. Each flower measures only about a quarter of an inch across. From Maine to Georgia and Texas westward to Arizona and British Columbia the common bushy plant lifts its rather erect, curving, feathery branches perhaps only a foot, sometimes above a man's head, from August till November, in such dry, open, sterile ground as the white heath aster also chooses.
No one not a latter-day, structural botanist could see why the Tall, Flat-top White Aster (Doellingeria umbella) is now an outcast from the aster tribe into a separate genus. This common species of moist soil and swamps has its numerous small heads (containing ten to fifteen rays each) arranged in large, terminal, compound clusters (corymbs). The stem, which rises from two to eight feet, has its long-tapering, alternate leaves hairy on the veins beneath and rough margined.
Late in the fall you may hear the rich tone of a Bombilius, one of the commonest flies seen about flowers, as he darts rapidly among the white asters. Unless you have been initiated, you may mistake this fly for a bee. He sings a very similar song and wears a similar dress; but he is not a very good imitation, after all, and a little familiarity with him will give you courage to catch him in your hand if you are quick enough, for he is incapable of stinging or biting: he can merely make a noise out of all proportion to his size. He is simply living from hour to hour, and lays up no store for the winter, enjoying more or less security from his resemblance to the industrious and dangerous insect which he imitates.