Montana Field Guide

Spiny Hopsage is a rounded, profusely branched shrub that is up to 15 dm high and has erect or spreading, gray-barked, spine-tipped stems. The fleshy, broadly lance-shaped leaves are 10-25 mm long and have entire margins and a short stalk. Foliage is covered with small, star-shaped hairs that easily rub off. Male flowers are on different plants than females flowers, making the plant dioecious. There are 2-5 small, green, sessile male flowers that are 1-2 mm long with a 4-lobed calyx, 4 stamens, and no petals; they occur in the axils of the smaller upper leaves, or bracts. Female flowers are arranged in small spikes in the upper leaf axils. Each flower has an ovary surrounded by 2 green, nearly circular bracts. When mature, the bracts enlarge to be 8-15 mm wide; they are pale to red with thin margins.

Flowering and fruiting in May-June.

Atriplex canescens is similar in appearence, though the combination of fleshy leaves with circular, entire-margined, female fruiting bracts distinguishes Grayia spinosa.

Dry shrublands in the valleys and foothills usually on sandy-textured, alkaline soils at elevations below 5,000 ft (5,600 ft near Gardiner). Typical associated species in Montana include Artemisia tridentata var. wyomingensis, Atriplex confertifolia, Stipa comata, Juniperus spp., Chrysothamnus nauseosus, Chrysothamnus viscidiflorus, Bouteloua gracilis and Sarcobatus vermiculatus.

Ecological characteristics specific to Monatana populations of Grayia spinosa are lacking though information for the species across other parts of its range is widely available.

Grayia generally occurs in small patches or as scattered shrubs. Plants initiate growth in early spring and rapidly complete their vegetative and reproductive cycles prior to entering summer dormancy. Though drought tolerant, it may fail to produce flowers during dry years. Germination occurs in the spring with seedling establishment usually occurring beneath the canopies of surrounding shrubs. Seed production is variable and regeneration tends to be episodic. Mature shrubs are most tolerant of wildfires after summer leaf fall and and posses the ability to resprout from surviving root crowns. Fruits are dispersed by wind, gravity, and insects (Daubenmire 1970, Shaw et. al. 1996).

Spiny hopsage is considered one of the most palatable shrubs in salt desert shrub communities in spring and early summer and is used as forage by sheep, goats, dear, pronghorn and rabbits. Its use by wildlife and livestock declines rapidly as plants enter summer dormancy. Although fairly tolerant of grazing, heavy use can have negative impacts on survivorship (Blaisdell and Holmgren 1984).

Growth of cheatgrass (Bromus tectorum) beneath spiny hopsage canopies can interfere with regeneration and promote increased fire frequencies and shrub mortality by increasing fine fuel loads.

STATE THREAT SCORE REASON
Reported threats to Montana's populations of Spiny Hopsage (Grayia spinosa) are currently assigned as unknown. Potential threats due to activity related to oil and gas development or competition with Cheatgrass need to be substantiated before a threat rank can be assigned (MTNHP Threat Assessment 2021).