Trees of Vancouver Island


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Trees of Vancouver Island


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Introduction

Vancouver Island is located off the west coast of British Columbia, Canada. There are 34 species of trees naive to the island, much fewer than on the mainland (Table 1). The lack of species in some cases can make identification much easier. In the case of pines, there are only two species, one of which has two needles per fascicle (Pinus contorta) and the other has 5 needles per fascicle (Pinus monticola ). There are only two species of true firs (Genus Abies) and they differ in foliage characteristics as well as geographic distribution. In the case of spruce, the island only has one native species (Picea sitchensis). If a conifer has hanging cones, it can only be a spruce, a hemlock, or a Douglas-fir.

Table 1. Conifer species that are native to Vancouver Island.
No. Group Species Common
Coniferous Trees
1 Fir Abies amabilis Amabilis Fir
2 Fir Abies grandis Grand Fir
3 Fir Abies lasiocarpa Subalpine Fir
4 Cypress Chamaecyparis nootkatensis Yellow-cedar
5 Juniper Juniperus scopulorum Rocky Mountain Juniper
6 Spruce Picea sitchensis Sitka Spruce
7 Pine Pinus contorta contorta Shore Pine
8 Pine Pinus monticola Western White Pine
9 False Hemlock Pseudotsuga menziesii Douglas-fir
10 Yew Taxus brevifolia Pacific Yew
11 Arborvitae Thuja plicata Western Redcedar
12 Hemlock Tsuga heterophylla Western Hemlock
13 Hemlock Tsuga mertensiana Mountain Hemlock

Table of Deciduous species
Table 1. (cont.) Deciduous species that are native to Vancouver Island.
Deciduous Trees
14 Maple Acer circinatum Vine Maple
15 Maple Acer glabrum Douglas Maple
16 Maple Acer macrophyllum Bigleaf Maple
17 Alder Alnus rubra Red Alder
18 Arbutus Arbutus menziesii Arbutus
19 Dogwood Cornus nuttallii Pacific Dogwood
20 Hawthorn Crataegus douglasii Black Hawthorn
21 Apple Malus fusca Pacific crab-apple
22 Cottonwood Populus balsamifera trichocarpa Black Cottonwood
23 Aspen Populus tremuloides Trembling Aspen
24 Cherry Prunus avium Red Alder
25 Cherry Prunus emarginata Bitter Cherry
26 Cherry Prunus virginiana Chokecherry
27 Oak Quercus garryana Garry Oak
28 Cascara Rhamnus purshiana Cascara
29 Willow Salix lasiandra Pacific Willow
30 Willow Salix sitchensis Sitka Willow
31 Ash Fraxinus latifolia Oregon ash
32 Ash Sorbus aucuparia Mountain Ash
33 Ash Sorbus sitchensis Sitka Mountain Ash


Conifer Identification

Refer to Conifers Key 1.

a dichotomous key to conifer genera
Conifers Key 1. Identification key to conifer genera.


A. The first step in identification is to determine the Genus of the species examined. To do this, examine the leaves first. Are the leaves needle-like (Fig. 1) or scale-like (Fig.2).

needle-like conifer leaves
Figure 1. Needle-like conifer leaves.
Scale-like conifer leaves
Figure 2. Scale-like conifer leaves.



Conifers with needle-like leaves

B. Next we examine how the needle attaches to the branchlet. Are single needles attached directly to the branchlet (Fig.1) or are they attached in clusters (Fig.3)?

Conifer needles that are attached in clusters.
Figure 3. Conifer needles attached in clusters.

Needle attachment

C. The next character to examine is how the needles are attached to the branchlet. Is there a wooden peg-like structure (sterigmata) that attaches the needle to the branchlet (Fig.4, Fig.5) or does the needle tissue attach directly to the branchlet (Fig. 6).
Conifers that have needles that are directly attached to the branchlet with a suction-cup-like base are in the Genus Abies, firs.

illustration of a spruce brnchlet showing sterigmata.
Figure 4. Spruce branchlet showing sterigmata.
Firs are mostly defined by two features 1) upright cones instead of hanging cones and 2) needles attached directly to the branchlet. Other characteristic features of firs will be discussed in the section on Abies.

Conifers that have needles that are not attached directly to the branchlet, may be spruce, hemlock, yew, or Douglas-fir. Among these genera however, the spruces (Picea) have the most easily observed defining characteristic, the sterigmata. These structures are easily seen when the needles have fallen off the branches leaving the peg-like sterigmata to roughen the surface.

spruce branchlet showing needles attached by sterigmata.
Figure 5. Spruce needles attach to the branchlet on sterigmata.
a fir branchlet showing needles attached directly to brnchlet.
Figure 6. Fir needles attached directly to branchlet.

With or without petiole

D. To determine difference between spruce and the others, we must look at the structure of the leaf. The petiole is the structure that attaches the leaf to the branchlet, what you might call a stem. In true firs (Genus Abies) the leaf is attached directly to the branchlet, in spruces there is a woody sterigmata that attaches the leaf to the branchlet, in the other Genera there is a petiole or a petiole-like structure that is intermediate between the leaf and the branchlet. The difference between spruce and hemlock, yew, and Douglas-fir, can be seen in the following figures.

Closeup of hemlock needles
Figure 7. Needle attachment in hemlocks.
Closeup of yew needles showing needles attached to a decurrent petiole.
Figure 8. Needle attachment in yews.
Closeup of Douglas-fir needles showing the leaf scar and the petiole.
Figure 9. Needle attachment in Douglas-fir.

Hemlock needles taper abruptly to a petiole that attaches to a small spur on the branchlet. The yew needles have a decurrent petiole that continues down the side of the branchlet after it joins (Fig. 8). Douglas-firs are distinguished from the others by the raised leaf scar and short petiole joining the needle to the branchlet (Fig. 9).

Conifers with clustered needles

E. Conifers with clusters of 2-5 needles (Fig. 10) that are bound together with a fascicle (Fig. 11) are in the Genus Pinus.

A cluster of pine needles
Figure 10. A cluster of pine needles.
a fascicle of pine needles.
Figure 11. A fascicle is a papery wrap that binds pine needles into a bundle.
Vancouver Island's native pine species

E. Pine identification on Vancouver Island is just a matter of counting the number of needles in a fascicle. If the fascicle has two needles it is a Shore pine (Pinus contorta var. contorta). This is the coastal variant of the Lodgepole pine Pinus contorta. Unlike the white pines, this species has small (30-50mm) round cones. If the fascicle has 5 needles, it is a Western White pine ( Pinus monticola ) and has long slender cones (100-250mm).






Conifers 2: Scale-like leaves

In this next section we look at trees that have scale-like leaves similar to those in Figure 2. Refer to Conifers Key 2.

a dichotomous key to conifers with scale-lie leaves
Conifers Key 2. Identification key to conifers with scale-like leaves.

A. First look at the cones. Are they fleshy berries (Fig.12) or are they woody cones (Fig.13)?
a juniper berry
Figure 12. A juniper berry
Yellow cedar cone
Figure 13. A Yellow cedar cone.

B. If the specimen has berry-like fruit, then it is a juniper. A Juniper berry is not a true berry; it is an unusual cone that has fleshy cone scales. Some junipers have "awl-like" leaves only (Fig.14) and others have awl-like and scale-like leaves (Fig. 2). Sometimes the awl-like leaves on the later are only on juvenile branchlets. On Vancouver Island only juniper with only awl-like leaves is the Common juniper (Juniperus communis), and it only occurs here as a low shrub.
Awl-like leaaves of a juniper.
Figure 14. Awl-like leaves of a juniper.

If the specimen has both awl-like and scale-like leaves and is a small tree, it is either a Rocky-mountain Juniper (Juniperus scopulorum) or the Seaside Juniper Juniperus maritima. The Seaside juniper was only recognized as a separate species in 2009, so many trees on Vancouver Island were recorded as Rocky Mountain juniper. The type location for this species is in Brentwood Bay, B.C. (Fig. 15), on a rocky point at the end of Stelly's Cross Road. The two species are almost impossible to tell apart except that Juniperus maritima has more cones that have exserted seeds (Fig. 16).

Type specimens of Seaside Juniper in Brentwood Bay
Figure 5. Type specimens of Seaside Juniper in Brentwood Bay.

Juniper cones showing exserted seeds
Figure 16. A juniper cone showing exserted seeds.

C. On Vancouver Island, trees with scale-like leaves and woody cones (Fig. 13) can be either Western redcedar (Thuja plicata) or Yellow cedar (Cupressus nootkatensis ). Although locally we call these species "cedars", they are not in the genus Cedrus which are "true cedars". True cedars are exotic to this area. True cedars have needle-like leaves in clusters and upright cones. It is helpful having only two species to choose from. If the cones are oblong (Fig. 17), the tree is a Western redcedar, and if the cones are globose, the tree is a Yellow Cedar (Fig. 18).

Western redcedar cones
Figure 17. Western redcedar cones a) green, b) mature.
Yellow cedar cones
Figure 18. Yellow cedar cones a) green, b) mature.





Conifers 3: Identification of conifers with single needle-like leaves

A. The conifers with single needle-like leaves (from Conifers Key #1) may have either hanging cones (Fig.19) or upright cones (Fig.20) (Conifers Key 3). Notice that in Figure 19 that Douglas-fir is spelled with a hyphen, which is because it is not a "true fir".

a dichotomous key to conifers with single needle-like leaves
Conifers Key 3. Identification key to conifers with single needle-like leaves.

a hanging Douglas-fir cone
Figure 19. A hanging Douglas-fir cone.
An upright true fir cone
Figure 20. An upright true fir cone.


B. Examine the needle cross-sections. Are they mostly square, and will roll between your fingers (Picea>: spruces), or are they rectangular and flat, so they will not? The only spruce on Vancouver Island can be distinguished from the Douglas-firs and hemlocks by their prickly needles, the shape of their cone scales, and their bark which forms flaky discs. This is helpful because Sitka Spruce needles tend to be more flat than other spruces.

a cross-section of a spruce needle
Figure 21. A typical spruce needle cross-section.
A fir needle cross-section
Figure 22. A typical fir needle cross-section.

C. Douglas-firs can be easily distinguished from hemlocks by the cones. The Douglas-fir cones have unusual bracts that show projecting between the scales. The three-pronged bracts look like the tail and back legs of a mouse that is hiding between the scales (Fig. 19). The cones are also longer than hemlock cones. The two hemlocks differ in both size and colour of their cones and by foliage characteristics. Western hemlocks (Tsuga heterophilla) has very small cones (5-30mm long) which are green when mature while Mountain Hemlock (Tsuga mertensiana) has larger cones (30-80mm long) which are purple when they are mature. Another difference is that Western hemlock foliage is looks "lacy" and has two alternating needle lengths, while Mountain hemlock has denser needle coverage and one needle length.

comparative lengths of hemlock and Douglas-fir cones.
Figure 23. Comparative length of Western hemlock, Mountain hemlock, and Douglas-fir cones.


D. After returning to "A" in Conifers Key 3, we now examine the characteristics of the three "true firs" that are found on Vancouver Island. On Vancouver Island most Foresters refer to both Abies amabilis and Abies grandis, incorrectly as "Balsam firs". The Balsam fir (note: Abies Balsamea) is an east coast species that does not occur naturally in British Columbia. The three true firs that occur on Vancouver Island are the Grand Fir (Abies grandis), the Amabilis Fir (Abies amabilis), and the Subalpine fir (Abies lasiocarpa).

The Grand fir can be distinguished from the others by the colour of it's mature cones; they are green (Fig. 25) while the cones of the Amabilis (Fig. 26) and Subalpine firs are blue/purple and by the pectinate arrangement of it's needles on the branchlets.

 an Abies grandis cone
Figure 25. A Grand Fir cone, Abies grandis.
An Amabilis fir cone
Figure 26. An Amabilis fir cone, Abies amabilis.

Resin canal location

E. The difference in the position of the resin canals can help distinguish between the Amabilis fir and the Subalpine fir. The resin canals in Abies lasiocarpa are are marginal (Fig.27) while those in Abies amabilis are median (Fig. 28). In addition, the Subalpine fir usually has a quite distinctive spire-like shape (Fig. 29)that is quite different from the mature Amabilis fir (Fig.30).

A cross-section of a fir needle showing the position of median resin canals
Figure 27. A cross-section of a fir needle showing the position of marginal resin canals.
A cross-section of a fir needle showing the position of marginal resin canals
Figure 28.A cross-section of a fir needle showing the position of median resin canals.
An image of the Subalpine fir, Abies lasiocarpa showing it's spire-like form
Figure 29. The Subalpne fir Abies lasiocarpa
An image of the Amabilis fir showing it's characteristic shape.
Figure 30.The Amabilis fir Abies amabilis.