Tuesday, December 24, 2013

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.