Rayless Groundsel, Rayless Ragwort: Senecio aronicoides
Stout Meadow Groundsel, Sweet-marsh Butterweed: Senecio hydrophiloides (Synonyms: Senecio foetidus, Senecio foetidus var. foetidus, Senecio foetidus var. hydrophiloides, Senecio oreganus) -
Alkali-marsh Butterweed, Water Groundsel: Senecio hydrophilus - Flower heads typically have 5 ray florets, but sometimes will have none.
Wood Groundsel, Woodland Groundsel, Woodland Ragwort: Senecio sylvaticus - Flower heads typically lacking ray florets, but occasionally 1-8 may be present.
Common Groundsel, Old Man, Old-man-in-the-Spring: Senecio vulgaris -