Picea

Trees evergreen; crown broadly conic to spirelike; leading shoot erect. Bark gray to reddish brown, thin and scaly (with thin plates), sometimes with resin blisters (especially in Picea engelmannii and P. glauca), becoming relatively thick and furrowed with age. Branches whorled; short (spur) shoots absent; twigs roughened by persistent leaf bases. Buds ovoid, apex rounded to acute, sometimes resinous. Leaves borne singly, spreading in all directions from twigs, persisting to 10 years, mostly 4-angled and square in cross section (to triangular or ± flattened), mostly rigid, sessile on peglike base; base decurrent, persistent after leaves shed, sheath absent; apex usually sharp-pointed, sometimes bluntly acute; resin canals 1–2. Cones borne on year-old twigs. Pollen cones grouped, axillary, oblong, yellow to purple. Seed cones maturing in 1 season, usually shed at maturity (persisting for several years in Picea mariana), borne mostly on upper branches, pendent, ovoid to cylindric, sessile or terminal on leafy branchlets and thus appearing ± stalked; scales persistent, elliptic to fan-shaped, thin, lacking apophysis and umbo; bracts included. Seeds winged; cotyledons 5–15. x =12.

Distribution

North temperate regions, North America, Mexico, Eurasia.

Discussion

Species ca. 35 (8 in the flora with 7 native and 1 naturalized).

Selected References

Roche, L. 1969. A genecological study of the genus Picea and seedlings grown in a nursery. New Phytol. 68: 505--554.

Taylor, R.J. and T.F. Patterson. 1980. Biosystematics of Mexican spruce species and populations. Taxon 29: 421--469.

Wright, J.W. 1955. Species crossability in spruce in relation to distribution and taxonomy. Forest Sci. 1: 319--349.

Lower Taxa

Picea abies, Picea breweriana, Picea engelmannii, Picea glauca, Picea mariana, Picea pungens, Picea rubens, Picea sitchensis

Key

1	Leaves flattened or broadly triangular in cross section; stomates occurring only on, or more conspicuously on, adaxial leaf surface; Alaska to California.	> 2
1	Leaves square in cross section; stomates occurring more or less equally on all leaf surfaces; widespread.	> 3
2	Leaf apex sharp-pointed; twigs glabrous; seed-cone scales elliptic to narrowly diamond-shaped.	Picea sitchensis
2	Leaf apex blunt, especially on older leaves; twigs finely pubescent; seed-cone scales fan-shaped.	Picea breweriana
3	Twigs pubescent; cone scales usually fan-shaped, broadest near apex; seed cones 2.3-4.5(-5) cm; mostly eastern or boreal.	> 4
3	Twigs mostly glabrous; cone scales usually ± diamond-shaped or elliptic, broadest near middle (broadest at apex in Picea glauca); seed cones (2.5-)3-16 cm; mostly western or boreal.	> 5
4	Seed cones 1.5-2.5(-3.5) cm; leaves 0.6-1.5(-2) cm, mostly blunt-tipped, glaucous, blue- to gray-green.	Picea mariana
4	Seed cones 2.3-4.5(-5) cm; leaves 0.8-2.5(-3) cm, mostly acute, sharp-pointed, not glaucous, yellow-green to dark green.	Picea rubens
5	Seed cones (10-)12-16 cm; leaves 1-2.5 cm, blunt-tipped; introduced and locally naturalized species.	Picea abies
5	Seed cones 2.5-11(-12) cm; leaves (0.8-)1.2-3(-3.5) cm, mostly sharp-pointed; native species.	> 6
6	Seed-cone scales fan-shaped, margin at apex q entire, apex extending 0.5-3 mm beyond seed-wing impression; leaves (0.8-)1.5-2(-2.5) cm.	Picea glauca
6	Seed-cone scales diamond-shaped or elliptic, margin at apex irregularly toothed to erose, apex usually extending 3 mm or more beyond seed-wing impression; leaves 1.2-3(-3.5) cm.	> 7
7	Seed cones 3-7(-8) cm; cone scales extending 3-8 mm beyond seed-wing impression; twigs finely pubescent.	Picea engelmannii
7	Seed cones (5-)6-11(-12) cm; cone scales extending 8-10 mm beyond seed-wing impression; twigs usually glabrous.	Picea pungens