Spruces or firs? Notes for the Sandias

Spruce or Fir? Cibola National Forest, New Mexico
Sandia Mountains, May 2021


Both spruces and firs are in the pine family (Pinaceae) and from a distance, I can't tell them apart. Both grow high in the mountains and are green and pointy. Up close, I look at the needles. Spruce needles are square in cross section, and roll easily between your forefinger and thumb. Fir needles are "flat" (wide and thin) in cross section, and don't want to roll between your forefinger and thumb. Many people use an adage to remember that difference. The version I learned is "Spruce square, fir flat." If you're not concerned with IDs down to the species level, this rule will get you a long way.


These days I'd like to know which species of spruce or fir I'm looking at, but so far it's a struggle.  According to the checklist of vascular plants for the Sandia Mountains, The Sandia Mountains include two species of fir, Abies bifolia (cork-bark fir) and A. concolor (white fir), and two species of fir, Picea engelmannii (Engelmann's spruce) and P. pungens (blue spruce). Because that's not complicated enough, Douglas firs, which are also found there, are not in Abies but in Pseudotsuga


According to the same checklist, "A few saplings of [blue spruce] have been planted along roads in the Sandia Mountains, but attempts to relocate a natural population were not successful." So I'm less concerned about that one.  As of the summer of 2021 I'm trying to learn my other local spruces and firs down to the species level, and will share what I learn on this page. If you don't see what you need, try again in a few months.

Spruce, fir, and Douglas Fir cones


Let's start with this image, a composite of ones drawn by Leta Hughey.* "Alpine fir" is a partial synonym for cork-bark (or corkbark) fir,** so the image shows the five spruce and fir species of the Sandia Mountains. I printed out this image, folded it, and stuck it in my day pack for future reference. Next I'll go over the individual species, including Elbert Little's comments in the publication where I found Ms. Hughey's drawings.

Englemann spruce, Picea engelmannii



Englemann spruce, Picea engelmannii. "Also called white spruce, mountain spruce, silver spruce ... narrow, pointed conical crown and horizontal or slightly drooping branches extending nearly to ground; or at timber line dwarfed and bushy. Twigs roughened by peglike bases of fallen needles; twigs and leaf bases usually hairy. Needles 4-angled, 5/8 to 1 1/4 inches long, pointed but not stiff, dark or pale blue green, with disagreeable odor when crushed. Cones 1 1/2 to 2 1/2 inches long, light brown, with papery scales more or less rounded and distinctly thinner at apex. Bark thin, with loosely attached scales or flakes, grayish to purplish brown."



Blue spruce, Picea pungens



Blue spruce (Picea pungens).  "Also called Colorado blue spruce, Colorado spruce, silver spruce ... conical crown of bluish foliage, at least on young trees and parts. Twigs roughened by peglike bases of fallen needles; twigs and leaf bases usually not hairy.  Needles 4-angled, 3/4 to 1 1/8 inches long, stiff and spine-pointed, dull blue green or silvery blue or becoming darker on older parts. Cones 2/12 to 4 inches long, light brown, with scales more or less straight across apex and not thinner. Bark rough and thick, furrowed into scaly ridges, gray or brown."

Douglas fir, Pseudotsuga menziesii




Douglas fir (Pseudotsuga menziesii). "Also called Douglas-spruce, red fir, yellow fir, common Douglas fir, Oregon pine (lumber) ... with open, broadly conical crown and drooping lower branches. Twigs slightly roughened by bases of fallen needles. Needles spreading on all sides of twigs or sometimes in 2 rows, short-stalked, flat, 3/4 to 1 1/3 inches long, rounded at apex, dark blue green. Cones 1 3/4 to 2 3/4 inches long, reddish brown, with thin, rounded scales and long, distinctive, 3-pointed bracts projecting beyond the scales. Bark rough and very thick, deeply furrowed into broad ridges, sometimes very corky, dark reddish brown or gray."

The best way I know to identify a "Doug fir" is to notice the distinctive cones on the ground beneath a mature tree. Unlike the cones of "true" firs (Abies), Douglas fir cones reach the ground in one piece. For branches that aren't way over your head, look for  short, soft needles in a bottle-brush arrangement, and for prominent brown buds at the tips of branches.  



White fir (Abies concolor). "Also called balsam fir, silver fir, white balsam ... pointed conical crown becoming irregular in age. Needles spreading and curved upward, flat, 1 1/2 to 2 1/2 inches long, usually blunt, pale blue green or silvery. Cones in top of tree, upright, 3 to 5 inches long, usually grayish green, with scales falling apart at maturity. Bark on small trunks smoothish, gray, becoming very thick, hard, and deeply furrowed into scaly ridges.

White fir is the spruce/fir I encounter most often in the Sandias. White firs have both male and female reproductive parts. Easy to tell those apart, though. The female reproductive cparts become the cones at the top of the tree; those are large and often upright. (One mature they fall apart, so don't expect to find cones from previous years.) The male flowering parts are small and inconspicuous, and on lower branches. There's a reason for the arrangement: pollen is more likely to drift down than up, so each tree's female flowers (high up) are unlikely to be pollinated by its own male flowers (low down). 



Subalpine fir (Abies lasiocarpa). Little refers to this as alpine fir, "Also called white balsam, white fir (lumber) ... dwarfed and shrubby at timber line. Crown long, narrow, and sharp-pointed, with branches extending nearly to base of tree. Crown long, narrow, and sharp-pointed, with branches extending nearly to base of tree. Needles spreading or sometimes in 2 rows, 1 to 1 3/4 inches long, blunt, or on uppermost branches pointed and shorter, dark blue green. Cones in top of tree, upright, 2 1/2 to 4 inches long, dark purple, finely hairy, with scales falling apart at maturity. Bark becoming fissured and scaly, gray; in the variety corkbark fir, bark soft, spongy or corky, smoothish, thin, creamy white."

*The images appear on Pages 19 and 21 of Southwestern Trees: A Guide to the Native Species of New Mexico and Arizona (1950; reprinted 1968), by Elbert L. Little, Jr.  Agricultural Handbook No. 9. USDA Forest Service; U.S. Government Printing Office, Washington, D.C. The report is available online. Ms. Hughey was not listed on the title page but was credited on Page 4.


**Abies lasiocarpa, the subalpine fir or Rocky Mountain fir, includes a regional variant, cork-bark or corkbark fir, in Arizona and New Mexico.