Stout Meadow Groundsel, Sweet Marsh Butterweed, Sweet Marsh Groundsel: hydrophiloides (Synonyms: Senecio foetidus, Senecio foetidus var. foetidus, Senecio foetidus var. hydrophiloides, Senecio oreganus) - Tall, erect plants with one to many stems clustered close together. Basal leaves are elliptic to oblanceolate. herbage is glabrous or smooth.
Alkali Marsh Butterweed, Alkali Marsh Ragwort, Great Swamp Groundsel, Water Groundsel: Senecio hydrophilus (Synonym: Senecio hydrophilus var. pacifica) - Tall erect plants with long, narrow leaves, and clusters of thin flower heads with disk flowers (occasionally ray flowers) found at the apex of the stems.
Common Groundsel, Common Tansy, Old-Man-in-the-Spring: Senecio vulgaris - Small, weak-stemmed plants with small, pinnatifid leaves. Flower heads thin with black tips to the bracts.