Montana Field Guide

PLANTS: Aromatic shrubs of 10–40 cm tall (Lesica et al. 2012) that sprout from roots (FNA 2006). Stems are gray-green to brown, brittle, and glabrate (FNA 2006). Plants are glabrate to tomentose, and sometimes with obscure resin dots beneath the tomentum (FNA 2006; Lesica et al. 2012).

LEAVES: Aromatic, gray-green, wedge-shaped (cuneate), 5–25 mm long, and tipped with 3 lobes (FNA 2006). Upper leaves are densely hairy (not sticky) (FNA 2006). Leaves on flowering stems are deciduous while those on non-flowering stems are persistent (FNA 2006).

INFLORESCENCE: Spiciform with linear bracts (Lesica et al. 2012).

In Montana we have subspecies arbuscula and longiloba (refer to Habitat, Phenology & Diagnostic Characteristics).

Subspecies arbuscula flowers from mid- to late summer (FNA 2006), which in Montana is mid-August to September (Lesica et al. 2012).

Subspecies longiloba flowers from early to late spring (FNA 2006), which in Montana is from July to mid-August (Lesica et al. 2012). Its ability to begin blooming as snow melts in the spring is a unique characteristic for the subgenus Tridentatae (FNA 2006).

Refer also to Phenology.

Subspecies arbuscula has leaves with acute lobes and stiffly erect to ascending stems (Lesica et al. 2012). Leaves are broadly cuneate (lobes less than half the blade length, 1-3 mm wide, and rounded) (FNA 2006). The involucres are 3.5-4 mm tall and 2-4.5 mm in diameter (FNA 2006). Plants are found on stony calcareous soil (Lesica et al. 2012)

Subspecies longiloba has leaves with rounded lobes and flexuous, prostrate-spreading stems (Lesica et al. 2012). Leaves are broadly cuneate (4-10 mm by 2-5 mm, often irregularly lobed, with rounded lobes, and middle lobes overlapping lateral lobes) (FNA 2006). The involucres are 2-3 mm tall and 1.5-2.5 mm in diameter (FNA 2006). Plants are found on fine-textured soil of stream terraces (Lesica et al. 2012). Ecologically it is distinguished from other subspecies by growing at low elevations in fine-grained clay soils (FNA 2006).

Subspecies arbuscula plants are found rocky sedimentary soils in high valleys and mountain slopes at elevations from 1500 to 3800 meters (FNA 2006). In Montana plants occur on stony calcareous soil (Lesica 2012).

Subspecies longiloba plants are found on clay soils of alkaline basins and valleys, occasionally on outwash plains of mountains, at elevations from 1500 to 2500 meters (FNA 2006). In Montana plants occur on fine-textured soil of stream terraces (Lesica et al. 2012).

Greater Sage-grouse are known to eat Artemisia arbuscula ssp. arbuscula (Boyle and Reeder 2005).

Artemisia arbuscula flowers (heads): The involucre is campanulate, about 2–5 mm high with green, tomentose phyllaries (Lesica et al. 2012). The receptacle is glabrous. Heads consist of 4-8 perfect (contains both male and female structures) disk flowers that are glabrous or glandular; Corolla is about 2 mm long (Lesica et al. 2012). Achenes are resinous and less than 1 mm long (Lesica et al. 2012).

The involucres for subspecies arbuscula are 3.5-4 mm tall and 2-4.5 mm in diameter (FNA 2006).
The involucres for subspecies longiloba are 2-3 mm tall and 1.5-2.5 mm in diameter (FNA 2006).