Eupatorium sessilifolium var. brittonianum

Native

Minnesota threatened species

Dry. Oak woodland edges.

August to September

White

2′ to 5′

This is a 2′ to 5′ tall, erect, perennial forb that rises on a single stem from a short caudex or rhizome.

The stem is erect, sparsely branched near the top, and leafy. It is hairless except in the inflorescence.

The leaves are opposite, sometimes alternate near the top, hairless, dotted with glands, and lance-shaped. They are mostly stalkless or are attached to the stem on short leaf stalks. The bases are usually broadly rounded, sometimes squared off, but do not wrap around the stem. They taper from above the base to a point at the tip. They are 2 to 5 times as long as wide. The lower leaves are 2¾″ to 6″ long and ⅓″ to 1⅛″ wide, becoming smaller as they ascend the stem. The veins are arranged like the vanes of a feather, with a single prominent midvein extending from the base to the tip and lateral veins originating from several points on each side (pinnately veined). The blade margins have sharp, forward-pointing teeth all the way to the base.

The inflorescence is a branched, widely-spaced cluster of flower heads at the end of the stem and stem branch.

The flower heads are cylinder-shaped. Each flower contains 5 or sometimes 6 disk florets and no ray florets. Each disk floret consists of a white flower tube with 5 short, spreading lobes. A white, forked style protrudes from the floral tube well beyond the lobes.

The fruit is a tiny dark achene with a small tuft of 30 to 40 hairst.

Canada goldenrod (Solidago canadensis) is similar in appearance when not in bloom.

Common boneset (Eupatorium perfoliatum var. perfoliatum) leaves are fused around the stem at their bases. They have a conspicuous network of veins, depressed on the upper surface of the blade, giving the blade a wrinkled appearance. The leaf margins have rounded teeth. Each flower contains 9 to 23 disk florets. The flowers are fragrant. The fruit has a tuft of 20 to 30 hairs. It occurs in wetter habitats.

Tall boneset (Eupatorium altissimum) leaves are pointed at both ends. They have 3 prominent lateral veins. The leaf margins are untoothed near the base, toothed above the middle. Each flower contains just 5 disk florets.

White snakeroot (Ageratina altissima var. altissima) leaves are shorter, wider, and on long leaf stalks. The flower heads are much larger.