1. Primary umbels with ca. 70-120 rays; undersides of leaves with the main veins with sparse, short, straight spicules or nearly glabrous; reddish oil canals on the fruit up to 0.5-0.9 mm wide, extending ca. 75% of the way from apex to base of the fruit.

H. mantegazzianum

1. Primary umbels with ca. 10-50 rays; undersides of leaves with the main veins pubescent with straight to curly hairs; reddish oil canals on the fruit mostly less than 0.5 mm wide, extending ca. 50-60 (-70)% of the way from apex to base of the fruit.

2. Basal leaves merely ternate; leaf rachises with slender, often reflexed or curly hairs mostly not more than 1 mm long.

H. maximum

2. Basal leaves clearly pinnate; leaf rachises with thick, spreading hairs up to ca. 2 mm long.

H. sphondylium