Solidago altissima
From Connecticut Botanical Society
Canada goldenrod is a variable plant. The species Solidago canadensis now includes tall goldenrod (Solidago canadensis var. scabra), which was formerly considered to be a separate species (Solidago altissima).
Family: Aster (Asteraceae)
Habitat: roadsides, clearings, thickets
Height: 1-5 feet
Flower size: flowerheads 1/8 inch high, in plume-shaped cluster 3-5 inches across
Flower color: yellow
Flowering time: July to September
Origin: native