Picea

Spruce needles fall readily from a prominent peg-like projection on the twigs. Black spruce is the usual host of dwarf mistletoe, Arceuthobium pusillum Peck, although the parasite has occasionally been found on white spruce in the vicinity of the Straits of Mackinac (and rarely on Larix and 2-needled Pinus elsewhere in the Great Lakes region).

1. Young branchlets ± densely fine-pubescent; leaf bases below the peg-like projections ± obscure on 1-year-old twigs; female cones rather spherical, (1–) 1.5–2.8 (–3) cm long, the scales with slightly irregular or erose margins.

P. mariana

1. Young branchlets glabrous; leaf bases prominent below the peg-like projections on 1-year-old twigs, appearing to cover them with ridges and grooves; female cones cylindrical, (2.5–) 3–18 cm long, the scales nearly or quite entire (except in P. pungens, with female cones 5–12 cm long).

2. Female cones ca. 10–18 cm, leaves somewhat flexible when live, pointed forward along twigs, green, branchlets pendulous on mature trees.

P. abies

2. Female cones (2.5–) 3–10 cm; leaves stiff, spreading, often somewhat glaucous, branchlets spreading.

3. Leaves acute to acuminate, but mostly with the ultimate tip blunt; female cones (2.5–) 3–6 cm long, the scales with the outer margins entire.

P. glauca

3. Leaves (at least some of them) with a sharp acuminate tip; female cones ca. 6 –10 cm long, with the outer scale margins irregularly toothed.

P. pungens

All species found in Picea

Picea abiesNORWAY SPRUCE 
Picea glaucaWHITE SPRUCE 
Picea marianaBLACK SPRUCE 
Picea pungensBLUE SPRUCE 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. August 17, 2017. http://michiganflora.net/genus.aspx?id=Picea.