Flower:

Open, branching clusters of stalked flowers at the top of the stem and arising from the upper leaf axils with 1 to a few to many flowers per plant. Flowers are about 1 inch across with 20 to 50 narrow petals (ray flowers) and a yellow center disk that turns purplish with age. Ray color is white to pale blue or pinkish.

The bracts (phyllaries) surrounding the base of the flower are in 4 or 5 layers, hairless except for a few minute hairs around the edge, very narrow, sharply pointed often with a spot of purple at the tip, and usually of varying lengths, with the outer phyllaries shorter than the inner and sometimes flaring a bit. Flower stalks are hairless or with lines of hairs, and with 1 to a few small leaf-like bracts below the flower.

Leaves and stems:

Leaves are mostly ascending, lance-linear, 1 to 6 inches long, mostly less than ¼ inch wide, toothless or with a few small teeth, hairless except for sparse hairs on the midvein on the underside and minute hairs around the edge. Basal leaves are broader, more variable in shape, have winged, sheathing stalks, and wither away by flowering time along with the lower stem leaves. Mid and upper stem leaves are stalkless and nearly clasping.

Stems are single or multiple from the base, erect to ascending, green to reddish, unbranched except in the flowers, hairless in the lower plant with lines of short hairs on the mid and upper stem and into the flowering branches.

Fruit:

Fruit is a dry seed with a tuft of white hair to carry it off in the wind.

Notes:

Found primarily in wetland habitats, Northern Bog Aster is often a pretty spindly plant. It most closely resembles Panicled Aster (Symphyotrichum lanceolatum), which has proportionately broader leaves up to ¾ inch wide, smaller flowers ¾ inch or less, found in more varied habitats, and is often rather robust with over 100 flowers.