Blue stem. Flowers in small isolated clusters strung out along the stem. Usually a single stem.
Similar species: Zigzag Goldenrod (Solidago flexicaulis) - also grows in woods; leaves are larger, more deeply toothed; stem thicker. Hairy Goldenrod (Solidago hispida) - stem is very hairy/downy. Gray Goldenrod (Solidago nemoralis) - short and stem is grey, downy.