Eurybia divaricata, White Wood Aster
Very common in Piedmont woods, rare on the coastal plain. The larger leaves are stalked, heart-shaped, about 4" long.
Eurybia schreberi, Schreber's Aster
Similar to E. divaricata, but the plant tends to be larger, and has separate tufts of very large basal leaves, some over 6" long. Piedmont only, rare.
Eurybia compacta, Slender Aster (Aster gracilis)
Leaves not heart-shaped, stem leaves stalkless, 8-12 purple ray flowers (petals). Coastal plain only.
Eurybia spectabilis, Showy Aster
Leaves not heart-shaped, stem leaves stalkless, 15-30 purple ray flowers. Coastal plain only, rare.
This species is historical in Delaware:
Eurybia radula, Rough-leaf Wood-aster
Formerly found on the coastal plain.
Sources: The Flora of Delaware, Herbaceous Plants of Maryland.