Rayless Groundsel, Rayless Ragwort: Senecio aronicoides - Discoid flower heads only. No ray flowers.
Elmer's Ragwort: Senecio elmeri -
Dwarf Mountain Ragwort, Dwarf Mountain Groundsel, Low Mt. Butterweed: Senecio fremontii var. fremontii -
Tall Groundsel, Sweet Marsh Butterweed, Stout Meadow Groundsel: Senecio hydrophiloides (Synonyms: Senecio foetidus, Senecio foetidus var. foetidus, Senecio foetidus var. hydrophiloides, Senecio oreganus) -
Alkali Marsh Butterweed, Alkali Marsh Ragwort, Great Swamp Groundsel, Water Groundsel, Water Ragwort: Senecio hydrophilus (Synonym: Senecio hydrophilus var. pacifica) -
White Western Groundsel, Tall Western Groundsel, Lambstongue Ragwort, Lamstongue Groundsel: Senecio integerrimus var. exaltatus (Synonyms: Senecio integerrimus var. vaseyi, Senecio vaseyi) -
Bigheaded Groundsel: Senecio integerrimus var. major -
Paleyellow Ragwort, Western Groundsel, White Western Groundsel: Senecio integerrimus var. ochroleucus (Synonyms: Senecio integerrimus ssp. ochroleucus, Senecio lugens var. ochroleuchus) -
Tansy Ragwort, Stinking Willie: Senecio jacobaea (Synonym: Jacobaea vulgaris) -
Black-tipped Groundsel: Senecio lugens (Synonym: Senecio integerrimus var. lugens) -
Wood Groundsel, Woodland Groundsel, Woodland Ragwort: Senecio sylvaticus -
Arrowleaf Groundsel, Arrowleaf Ragwort: Senecio triangularis var. triangularis (Synonyms: Senecio gibbonsii, Senecio triangularis, Senecio triangularis var. angustifolius) -
Sticky Ragwort: Senecio viscosus -
Old-man-in-the-Spring, Old Man in the Spring, Common Butterweed, Common Groundsel: Senecio vulgaris - Discoid heads only. No ray flowers.