The Artemisia genus contains an army of allergenic plants, most of which are called wormwood, sagebrush or mugwort. According to Pollen Library, they may be the top overall source of pollinosis after ragweed and grasses. Artemisia absinthium (pictured) is also the main ingredient in absinthe.
Habitat: Temperate climates around the world, usually in dry or semi-dry habitats (including much of the Western U.S.)
Description: Aromatic, bitter herbs and shrubs, varying in height from 1 to 10 feet
Allergy season: Midsummer to fall
Tips: Ragweed gets more attention, but midsummer and fall are also when Artemisia plants erupt with romance. Watch out for multiple species blooming close together, since one study found "very strong in-vitro cross-reactivity" within the Artemisia genus.