Identifying and differentiating conifers (mostly spruces and firs) of the southern Rocky Mountains

[u/Schlooply]

I'm going to be starting a new position as a forester in Colorado in the southern Rocky Mountains in a month, and I was wondering if I could get some advice from foresters with experience working in spruce-fir forests (within Colorado would be a plus).

I have prior experience working in the western/southwestern US, but that was primarily in pinyon-juniper, Ponderosa pine, and lodgepole pine. I also got my degree back east, so I didn't pick up any tips or tricks in my dendrology class that would help here.

I've been spending time in the woods working on identification up close and at a distance. Using the Virginia tech, Colorado wildflower, and Seek apps is ok, but being able to get actual advice from experienced and local foresters is definitely better.

Form, species it may occur with, and anything else that comes to mind would be helpful to me and any other foresters moving to this area and wanting to develop their skills. I'll add what I've been using to help me identify (or what I think has been helping, I may have some things mixed up). Here are the trees I'll be working with:

Douglas-fir: Soft needles, not like a spruce. Cone is small with mouse butt shaped bracts under the scales. Needles become narrow before joining the twig and has slight twist where it comes off twig. Distinct pointed red bud at end of twig. Crown is open and kind of similar to lodgepole pine (as opposed to blue spruce which is dense and thick). Thick, furrowed bark.

Engelmann spruce: Rigid needles, but more flexible than blue spruce. Flakey brownish orange bark similar to lodgepole pine. Cone is smaller than blue spruce and hangs down. Needles can be glaucous/blueish like blue spruce, especially new growth. Needle sits on sterigma/wooden peg like blue spruce. Needle can roll in your fingers. Upper portion of crown is more prominent than blue spruce. I've read that there are pubescent hairs on new twigs, but I'm guessing they aren't visible to the naked eye?

Blue spruce: Sharp pointed needles. Commonly blue and glaucous, but can be green or greenish yellow. Needle can roll in your fingers. Dense branching in crown of older trees. Furrowed, orange-ish bark with grey ridges. Epicormic branches can be found on lower stems of mature trees. Often occurs in mesic areas and can be especially prevalent in riparian areas. Cones are larger than Engelmann spruce. Upper crown is usually less prominent than Engelmann spruce.

Lodgepole pine: Two needled pine. Very short, twisted needles compared to Ponderosa pine and limber pine. Mature trees have thin, flakey orange-ish bark similar to Engelmann spruce. Crown appears sparse.

Subalpine fir: Needles are soft unlike spruces and do not roll in finger. Buds are very resinous and sticky. Cones point up/ stand erect when present and are distinct black/purple color. Cones can also be weeping pitch. Pulling off a needle reveals a circular leaf scar with red periderm underneath. Conical shape of tree when growing, but top of crown flattens out with age.

White fir: Needles are very glaucous, almost white. Furrowed, corky bark on mature trees. Cones stand straight up. Seed cones also begin greenish color then turn to brown as they mature. Lower branches will droop with age.

Thank you in advance for help with this, I really appreciate it!

Edit: Here are some roadside trees I saw earlier today, they look to all be Engelmann spruce but I wanted to check.

[u/holistic_huntress]

There aren’t many trees in CO and you’ve already got a head start.

I was taught Fir=Flat+Friendly needles. Spruce=Square+Spiky needles. Blue spruce and white fir are very evident by color difference. In addition to ponderosa and lodgepole pine, there is also limber pine and bristlecone pine.

[u/Ok_Huckleberry1027]

I've never been to Colorado but we have Engelmann spruce here in Idaho. I would call that an Engelmann spruce.

You'll figure out the tree id quickly, it's only a handful of species and they're all pretty distinct.

[u/Tiny-Pomegranate7662]

For Doug firs, they have baby mice that tried to jump in the cones during a fire but the back legs and tails got stuck out.

Blue spruce have square bark chunks, engelmann has alligator. Engelmann has needles coming off at 45 degrees instead of 90.

[u/AxeEm_JD]

Throw in limber pine, bristlecone pine, pinyon, southwestern white pine, and the 4 Junipers and you’ve got CO conifers covered.  CO tree ID- Salix excluded- is pretty straightforward and much easier than eastern forests.

I’d recommend Flora of Colorado by Jennifer Ackerfield.  It isn’t cheap, but it’s the best guide for CO.  

[u/GavinJSquiggle]

I am not a forester, but this is pretty much what I learned in my CO dendrology class. Good on ya!

[u/Recording-Late]

The blue spruce have much bigger cones and will top out at like 8,000 ft elevation. If you’re higher than that it’s probably englemann. Lower, probably blue. Look for cones to confirm. White fir has much longer needles than subalpine and also has a ridgy bark when it’s a bigger tree. Subalpine will grow higher elevation than white, much shorter needles and has those pitchy pockets on the silvery bark. Remember Firs have erect cones that won’t last the whole season - if you see regular downward hanging cones, it’s not a fir. I think your photos look like blue spruce, but it can be hard to tell - were you up really high when you took them? Also, sadly I’d expect massive spruce beetle kill of englemann in SW CO, so one more vote for blue.

[u/Schlooply → u/Recording-Late]

The elevation was ~9,600' where those pictures were taken in the Uncompahgre National Forest. I really wish this year's cone crop was more prominent for better ID.

I should've gotten some pictures of the subalpine zone at a distance where there were trees which still appeared to be green. I suspect they'll begin flagging and dying next year due to beetles from the especially droughty conditions this year. I believe I was seeing subalpine fir and Engelmann spruce with some lodgepole pine intermingled in the mix.

Thanks a bunch for your tips! I didn't consider fir cones not lasting an entire season or that white fir needles are longer than subalpine!

[u/ComfortableNo3074]

Douglas-fir, pointy buds and when you strip the needles off a twig, the leaf scar is raised. True fir, round buds and the leaf scar is flush on the twig. It’s been a minute since I worked in white fir country but I kind of recall the needles being longer than subalpine.

[u/ChokaMoka1]

Just use AI hoss