What Christmas tree is that? A guide to common species

Christmas trees come in many shapes, colors, and species these days.  In the old days you went out into the forest and cut a little (usually rather scraggly-looking) tree of some native tree in your local forests.

Postage stamp from Åland (between Sweden and Finland) showing people
(with saw in hand) bringing home the Christmas tree.
(c) Posten Åland, fair use (link)

For example, in Northern Europe you have only one local species of pine (Scots Pine, Pinus sylvestris), and only one spruce species (Norway Spruce, Picea abies), so a wildcut tree would be one of those species. Unless you brought in a juniper of course (Juniperus communis). In North America there are more local conifers to choose from, but still mostly only a handful.  But these days things are not so simple.

Nowadays, the Christmas tree plantations grow a wide variety of conifer species that might not be local to your area. If you get a tree from a supplier, then the tree might come from far away.  So, finding out what tree you have standing in your living room might not be that simple.

The National Christmas Tree Association has nice photos and descriptions of the most common species. Brooklyn Botanic Garden also has a great clickable key to Christmas tree species with images and descriptions of 15 common species. (Update: Max Payne also has a nice page with descriptions of common Christmas tree species, including several Cupressaceae species.)

First, most Christmas trees are either FIRS (Abies), SPRUCES (Picea), DOUGLAS FIR (Pseudotsuga). or PINES (Pinus). All of these are conifers and have leaves called needles, and cones (except, you rarely see cones on young trees used for Christmas). These plants are quite easy to tell apart and they all belong to the pine family, Pinaceae. See key below.

US Postal stamps showing balsam fir, blue spruce, ponderosa pine and eastern red cedar.
(c) USPS, fair use (link)

Identification key to common Christmas tree genera

1a. Are the needles clustered 2-5 together? Yes - it is a pine (Pinus).
1b. Are needles single? Yes - it is a fir, douglas fir, or spruce. Go to 2.  

2a. Are the needles square in cross-section and green underneath? Yes - it is a spruce (Picea).
2b. Are the needles flat in cross-section and have two white bands underneath? Yes - it is a fir or douglas fir. Go to 3.

3a. The buds at the end of each branch have a sharp tip and are elongated. Yes - it is a douglas fir (Pseudotsuga).
3b. The buds at the end of each branch are blunt at the apex and round. Yes - it is a fir (Abies).

White pine.
Public domain image by Hardyplants, Wikipedia.

PINES (needles grouped in 2-5's)
Needles 5 together: 

• White pine (Pinus strobus) - green to bluish green, needles 5 together, 5-12 (2-4") cm long

Needles 2 together:

• Scots pine [older name: Scotch pine] (Pinus sylvestris) - green, sometimes silvery, needles 2 together, 4-7 cm (2-3") long
• Virginia pine (Pinus virginiana) - green to yellowish green, needles 2 together, 4-7 cm (2-3") long

Norway spruce branch.
(cc) Wikipedi, Wikipedia.

SPRUCES (needles single, square in cross-section, no white bands below each needle; each needle attached to the branch on a little outgrowth; needles attached spirally around branch)

Bluish or greyish tree

• Colorado blue spruce (Picea pungens) - blue green, needles 2-3.5 cm (1-1 1/4") long, with sharp tip
• White spruce (Picea glauca) - bluish to bluish green or gray, needles 1-2 cm (3/8-3/4") long, with blunt tip

Green tree

• Norway spruce (Picea abies) - dark green, needles 1-2.5 cm (1/2-1") long (drooping branches)

Douglas fir branch with cones. The cones are unique,
look at those bracts hanging out betweenthe scales, nothing else looks like that.
(cc) Walter Siegmund, Wikipedia.

DOUGLAS-FIR (needles single, white bands below each needle)

• Douglas-Fir (Pseudotsuga menziesii) - green to blue green, needles soft, 2-4 cm (3/4-1 1/4") long
  

Needles of White Fir showing white lines underneath.
(cc) Walter Siegmund, Wikipedia.

FIRS (needles single, flattened; white bands below each needle; each needles attached directly to the branch; needles attached in two rows along branch)

Needles with two white lines above

• Concolor Fir [White Fir] (Abies concolor) - green to bluish green, needles 2-5 cm (1 1/4-2") long (needles with sharp apices)
•  Caucasian Fir ["Nordmann"] (Abies nordmanniana) -  dark green, needles 1.8–3.5 cm (2/3-1 1/2")

Needles green or silvery above, without lines

• Balsam Fir (Abies balsamea) - dark green, needles 1-4 cm (3/8-1 1/2") long (needles with blunt, notched apex)
• Fraser Fir (Abies fraseri) - silvery to dark blue green, needles 1-2 cm (1/2-1") long (twigs with red hairs)
• Grand Fir (Abies grandis) - green, needles 2-5 (1/2-2") cm long (twigs with grey hairs, needles with blunt, notched apex)
• Noble Fir (Abies procera) - silvery, needles 2-4 cm (1-1 1/2) inches long (needles turn upwards along branches)

(Not included in this blog post are cedars, junipers, and yew, since they are less common as Christmas trees.)
Post updated 28 January 2014 with new information provided by MF.

The New York Times: Restaurant NOMA in Copenhagen

In July 6, 2010, The New York Times published an article by Frank Bruni about the amazing and world-renowned restaurant NOMA in Copenhagen and the foraging of food products from wild plants by its chef, René Redzepi.  

The well-written article was accompanied by a slideshow named "In Copenhagen, Cooking without Rules", showing some of the nature-provided ingredients in chef Redzepi's food. Unfortunately the text accompanying some of the images were incorrect. The New York Times was notified about these errors, but has not yet corrected the information.

Screenshot from NY Times article, by BotanicalAccuracy.com.

Image text: "Axel berry shoots are among the various petals, leaves and shoots Mr. Redzepi integrates into his food."

The problem and its correction:  This appears to be whitebeam flower buds from a small tree named 'oxel' in Swedish, 'whitebeam' in English, and its scientific genus is Sorbus (in the rose family Rosaceae).  The flower buds on this photo are probably from either Sorbus aria (akselrøn in Danish, common Whitebeam in English) or Sorbus intermedia (seljerøn; Swedish whitebeam).  
     The rowan tree (Sorbus aucuparia, rönn in Swedish, almindelig røn in Danish) is closely related to these, but in my experience that never has white-hairy flower buds. I have found no record that this species has ever been called 'axel berry' or 'axel', in English, Danish, or Swedish for that matter.  
     I think the photographer misheard the Danish name 'akselrøn' or the Swedish name 'oxel' when he took notes and then never checked the typed up name with the source. The seeds in the fruits might contain cyanide, just like many other plants of this family, but the photo shows young flower buds.

Screenshot from NY Times article, by BotanicalAccuracy.com.

Image text: "Thuja cone"'

The problem:  This is not a Thuja (arborvitae) cone, it is a cone from a pine tree, most likely Scots Pine, Pinus sylvestris (Pinaceae), the pine species that is native to Denmark.  The photo shows an immature pine cone, before the seeds have formed inside it.  Pines are edible plants, even if they often have strong resin flavor.  Thuja is a member of the juniper family Cupressaceae, and it contains the chemical thujone, which you don't want to ingest too much of since it can be highly toxic.  The cones of the commonly cultivated arborvitae (Thuja occidentalis) look totally different, so there is no easy way to explain this inaccuracy in the information provided by The New York Times.

  (Both images are screenshots from the NY Times website used under fair use, photos © The New York Times.)

This post was updated with new information on 28 January 2014. Thanks MF for sending new information!