late goldenrod; Solidago gigantea
Canada goldenrod; Solidago canadensis
Both in the Asteraceae, of course.
Late goldenrod and Canada goldenrod grow in similar habitats. They’re both tall (late to 7 feet, Canada to 5 feet). They both have plume-like inflorescences and parallel-veined leaves. Late goldenrod has slightly larger flowers than Canada goldenrod. The main difference that I can see is in the stems: late has a slightly purplish stem (sometimes) that is (sometimes) covered with a white bloom:
while Canada goldenrod has a smooth, green stem:
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Here’s an overhead look at Canada goldenrod:
And here’s a closeup look at late goldenrod:
Tomorrow, the real culprit behind hayfever.
Elizabeth's Wildflower Blog 