Plant of the Week

Northern Wormwood (Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements var. Artemisia campestris L. ssp. borealis (Pallas) Hall & Clements var. wormskioldii (Bess. ex Hook.) Cronq. (Bess. ex Hook.) Cronq.)

By Russell Holmes

Northern wormwood is in the Asteraceae (composite) family, which is one of the largest vascular plant families with over 2,400 species in North America and 15,000 species worldwide. Composites occur in a wide diversity of habitats ranging from arctic polar deserts to hot Sonoran desert and alpine tundra to coastal salt marshes. Northern wormwood, by contrast, is a narrow endemic species with a worldwide range limited to the Columbia River physiographic province of Washington and Oregon.

Northern wormwood is a relatively low growing tap rooted biennial or perennial 5 to 15 dm (20 to 60 inches) tall with greenish to red stems covered by stiff hairs. Leaves occur in crowded rosettes, are 2.5 to 10 cm (1 to 4 inches) long, divided into 2 mm (0.1 inch) wide linear divisions, and are covered by dense silky hairs. Plants typically begin to flower in April but individual plants occasionally flower throughout the growing season. The inflorescence is narrow and spike-like to diffuse and panicle-like. Involucres are 2 to 4.5 mm (0.1 to 0.2 inches), relatively large compared to other varieties of A. campestris, and can be hairless to densely hairy. Flowers are pale yellow to yellow. Outer flowers are pistillate and fertile. Disk flowers are sterile.

The habitat where northern wormwood grows is generally arid with shrub steppe vegetation. Plants grow within the flood plain of the Columbia River and occasionally are flooded. Plants are generally sparsely distributed covering less than 1% of the suitable habitat at known sites.

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PLANTS Profile - Artemisia campestris ssp. borealis, northern wormwood