Here in New England, a showy group of plants commonly known as Asters graces the landscape in late summer and fall. While many of these species share similar characteristics, it's easy to sort out many of the species with the help of Newcomb’s Wildflower Guide. For example, take the following plant:
We start by answering the basic questions to obtain a 3-digit code.
Flower type: 7 or more Regular parts (7--)
Plant type: Wildflowers with Alternate leaves (73-)
Leaf type: Leaves Entire (732)
With this code, we can flip to the appropriate section of the locator key, which asks just one more question related to flower color before forwarding us to page 368. Here we find an Aster genus description that fits our plant. If we'd like to know which Aster this is, we'll need to flip to the special Aster section of the locator key. If you suspected this plant was an Aster from the start, you could've skipped right to the Aster section of the locator key.
From here, we can narrow things further. The larger leaves of our plant are (1) not both heart- or arrow-shaped and long-stalked, (2) obscurely toothed or entire, and (3) narrow or narrowly lance-shaped; and finally, our plant has flower heads 3/4 - 1 1/2" wide. Asters with these qualities are found on page 458-461.
Browsing the drawings and reading the written descriptions on these pages lead us to one match: Stiff Aster (Aster linariifolius)*. I found this short, perennial species growing in full sun in a large colony in dry, sandy soil.
I understand why newcomers to Newcomb's method may be a bit intimidated at first, but through a series of (typically) simple choices, it is possible to narrow down countless species to a single likely match. Give this a try on other Asters, and see if you agree.
*Note: Newer plant manuals, like Flora Novae Angliae by Arthur Haines (free online version at GoBotany), have reclassified native New England Asters into various genera within the Astereae family. Stiff Aster (A. linariifolius) has been reassigned to the genus Ionactis (or Stiff-asters) and is referred to as Flax-leaved Stiff-aster (I. linariifolius). Other native Asters have been relabeled as American-asters (genus Symphyotrichum), White-asters (genus Doellingeria), and Wood-asters (genus Eurybia). Tricky, tricky.