Groundsels and Butterweeds of the Columbia River Gorge
Sweet marsh groundsel (Senecio foetidus )
1. Sweet Marsh Groundsel Senecio foetidus var. foetidus (formerly S. hydrophiloides ): Tall, erect plants with one to many stems clustered close together. Basal leaves are elliptic to oblanceolate. herbage is glabrous or smooth.
2. Great Swamp Groundsel Senecio hydrophilus: 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.
3. Common Tansy Senecio vulgaris: Small, weak-stemmed plants with small, pinnatifid leaves. Flower heads thin with black tips to the bracts.