By Patsy Cotterill
Conifers: Part 2. The Pines
As described in Part 1 of this article (https://www.enps.ca/post/plant-talk-know-your-christmas-trees-conifers-part-1), pines (genus Pinus) can be recognized because their leaves are in clusters (bundles) of two, three or five needles, which are held together, at least initially, by a papery sheath at the base, as opposed to leaves attached singly to the twigs in most of our other conifer species. They can be distinguished from larches (genus Larix), whose leaves are also clustered, because they are evergreen, remaining on the tree for a variable number of years, depending on the species, whereas those of larches fall off in the autumn and are renewed in spring.
Pines have a more open look than spruce (the other locally common genus Picea), with branches spaced in whorls at regular intervals with the trunk visible between them. As well, the longer, bunched needles give the canopy a different appearance, discernible from a distance. Many pine species are tolerant of poor soils, but intolerant of shade. Regeneration is by seed, especially after fire.
Unlike the one or two cotyledons (seed leaves) of flowering plants, the seedlings of pines and conifers in general have multiple and varying numbers of cotyledons, making them look like little umbrellas. After the first year they gradually come to look more like little trees.
Pines, in common with all members of the pine family and many other species, form a symbiotic relationship with fungi in the soil. These ectomycorrhizal fungi form a dense mat enveloping the roots and assist in the tree’s access to water and minerals, while receiving carbohydrates, made in photosynthesis, from the tree.
There are 111 living species of trees and shrubs in the genus Pinus, which is divided into two subgenera: Pinus, the hard pines, and Strobus, the soft pines, with characteristics shown in the table below.
Subgenus Pinus (Hard Pines, Yellow Pine, Pitch Pines) | Subgenus Strobus (Soft Pines) |
2 or 3 needles in a bundle | 5 needles in a bundle |
2 longitudinal veins in leaf | 1 longitudinal vein in leaf |
Leaves usually stiff and sharp-pointed | Leaves usually soft and flexible |
Basal bundle-sheaths persistent | Bundle-sheaths falling off after first year |
Twigs ridged and grooved | Twigs smooth |
Cone scales often with prickles | Cone scales usually without prickles |
E.g.: lodgepole, jack, ponderosa, Austrian, Scots, Mugho | Eastern white pine, western white pine, limber, whitebark , bristlecone |
The Hard Pines (needles in bundles of two or three)
Lodgepole Pine (Pinus contorta var. latifolia)
Lodgepole is widely distributed across B.C. and the western part of Alberta, except for the western (coastal) strip of B.C. where it is replaced by another variety of the same species, shore pine (Pinus contorta var. contorta). This is a very different-looking tree: it is short and branched, and grows in bogs, sand dunes and on rocky ridges. Lodgepole pine often occurs in dense stands, covering large areas of mountain slopes, often following a fire, and tolerates a range of soils.
Lodgepole is a tall tree (reaching 60 m), known for its straight trunk, making it very useful for timber, including poles. The needles are in bundles of two, are 3-7 cm, long, twisted, not spread apart, stiff and sharp-pointed. The needles are bound together by a papery sheath at the base, which persists for the life of the leaf cluster.
Young bark is smooth and grey at first but becomes orange-brown and scaly with age. The branches are short and the crown is narrowly conical, especially in forest-grown trees. (I mention this because in Jasper National Park this year I initially mistook scraggly lodgepole pine killed by mountain pine beetle for skinny white spruce.)
Both pollen and seed cones are produced on the same tree, but in different parts of the crown, a feature which presumably reduces self-pollination. Pollination is effected chiefly by wind. Pollen cones are catkin-like, yellow or reddish, and formed in clusters at the base of new shoots, usually in the lower part of the crown. Vast quantities of pollen are produced, sometimes enough to form yellow drifts over large parts of the landscape. Seed cones are usually borne in the upper part of the crown near the tips of new shoots. They are short-cylindrical to ovoid, about 3-6 cm long at maturity and are attached in small clusters at right angles to the branch or point backwards to the base of the branch. (This is a key point of distinction from jack pine, in which the cones point forward towards the tip of the branch.) The cone scales are thick at the tips, with a curved prickle. They are held closed by resin, which is melted by the heat from either a fire or intense sunlight, releasing the seeds in large numbers. The cones can stay on the tree for 10-20 years.
Open-grown lodgepole pine (Pinus contorta var. latifolia) at Watson Creek Provincial Recreation Area near Cadomin, 2011-07-08. Photo: P. Cotterill.
Foliage and bark of lodgepole pine at Watson Creek Provincial Recreation Area near Cadomin, 2023-07-14. Photo: P. Cotterill.
Pollen (male) cones on planted lodgepole pine, Edmonton, 2024-06-15. Photo: P. Cotterill.
Backward-pointing (female) cones on lodgepole pine branch, Zeiner campground, Pigeon Lake, 2009-07-20. Photo: P. Cotterill.
Jack pine (Pinus banksiana)
This pine is transcontinental in occurrence but has the highest distribution towards the east. It barely appears in B.C. but is common in northern and central Alberta. In the Edmonton area, it occurs only on sandy soils, where it forms open stands in forests or, following regeneration after a fire, dense stands. Elsewhere it is associated generally with poor soils and rocky sites. Where the ranges of lodgepole pine and jack pine overlap in the west, hybrids occur.
The needles are in bundles of two, stiff and sharp-pointed as in lodgepole, but shorter at 2-4 cm long, and spread apart and more yellowish-green than those of lodgepole.
Seed cones are asymmetric and often curved, greyish-brown at maturity and in clusters of two to three. As previously stated, they point forward towards the tip of the branch. Cone scales are similarly thickened at the tip but lack a well-defined prickle. As in lodgepole pine, the cones remain on the tree for many years and require heat to induce opening of the scales and release of the seeds.
Lodgepole and jack pines are by far our commonest pines in Alberta and they are hard pines. Some other hard pines, which are non-native and planted as ornamentals, can be seen in our area.
Mature jack pine (Pinus banksiana) on Devon Sand Dune lands southwest of Edmonton, 2011-11-10. Photo: P. Cotterill.
Jack pine showing forwardly pointing seed cones, Halfmoon Lake Natural Area, 1997-08. Photo: P. Cotterill.
Jack pine seedlings regenerating after a fire a few years earlier, Opal Natural Area, 2022-06-16. Photo: P. Cotterill.
Scots pine (Pinus sylvestris) is native from western Europe to eastern Asia but is widely planted elsewhere for garden landscaping, erosion control and shelterbelts. Its patchy orange bark higher up on the trunk is very distinctive. A medium-sized tree to 30 m, its trunk is often crooked and the branches irregular. The paired needles are 4-8 cm long, twisted, stiff and sharp-pointed, bluish- to greyish-green. Seed cones are 2-5 cm long, usually lack prickles, and point backwards along the twig.
Austrian pine (Pinus nigra), native to southern Europe and mostly less than 30 m tall, is also commonly planted. The needles are longer than in Scots pine at 8-16 cm, straight and dark green. Seed cones are 6-8 cm long, oriented at right angles to the branch and have scales ridged with a small prickle.
Austrian pine (Pinus nigra) in a suburban garden, Edmonton, 2025-01-06. Photo: P. Cotterill.
Needle bundle and seed cone of Austrian pine, Edmonton, 2025-01-06. Photo: P. Cotterill.
Mugo pine (Pinus mugo), also native to southern Europe, is a common tree in older gardens and rights-of-way in Edmonton, usually appearing as a tall, multi-stemmed shrub. Its seed cones are 3-6 cm long, shiny, and arranged in small clusters at nodes almost at right angles to the branch. Scales have a dark brown ring surrounding the prickle at the tip. When the foliage is dense, house sparrows seem to love hanging out in this species!
Mugo pine in a suburban garden, Edmonton, 2025-03-06. Photo: M. Parseyan.
Mugo pine showing two-needled foliage and ripe seed cones, 2025-03-06. Photo: M. Parseyan.
The above three species all have needles in bundles of two.
Ponderosa pine (Pinus ponderosa) is another hard pine, but in this case there are typically three needles per bundle, although there can also be two or five. It is often planted in Alberta but is native to interior B.C., where it is an iconic tree of dry slopes and savannas and can reach a height of 35 m. The orange-brown bark on older trunks, deeply furrowed into flaky plates, is characteristic. The leaves are long (12-15 cm) and stiff like those of most hard pines, but also flexible. Seed cones are 7-15 cm long, pendulous and bear rigid, sharp prickles. Fire-tolerant, Ponderosa pine may occur in pure stands in which the trees are usually well spaced, or mixed with Douglas-fir and western larch.
Ponderosa pine (Pinus ponderosa), Creston, BC, 2024-08-14. Photo: P. Cotterill.
Three-needled foliage of Ponderosa pine, Stemwinder Provincial Park, BC, 2011-07-26. Photo: P. Cotterill.
Fallen seed cone of Ponderosa pine, Creston, BC, 2024-08-14. Photo: P. Cotterill.
The Soft Pines (needles in bundles of five)
Limber pine (Pinus flexilis)
This species occurs in a belt along the foothills and mountains of southern Alberta, often growing singly or in small groups on hill tops or rocky ridges, from the latitude of the junction of Jasper and Banff National Parks southwards, as well as in areas of B.C, from 1000 m elevation to treeline. The trees are small (up to 12 m), slow-growing and long-lived. The short, thick trunks are usually crooked in mature trees; the long, low branches give a shrub-like appearance. Limber pine is named for the flexibility of its young branches. Seed cones are 8-20 cm long and the scales, which lack prickles, open on the tree to release the seeds.
Limber pine (Pinus flexilis) on rocky outcrop, Kootenay Plains, 2010-06-22. Photo: P. Cotterill.
Limber pine with immature cones, Skyline Road, SW Alberta, 2006-06-10. Photo: P. Cotterill.
Whitebark pine (Pinus albicaulis)
This species is also a slow-growing, long-lived pine of the mountains of Alberta and B.C., occurring from 1000 m to the treeline. Its height depends on where it grows. It can be an almost prostrate shrub under harsh high alpine conditions; at lower elevations it is a small, multi-stemmed tree and, in even more favourable locations, a single-stemmed tree to 20 m tall. Also a tree of rocky areas and cliff faces, it often occurs as scattered clumps.
The needles in this species are 4-9 cm long and rather stout and stiff. Cones are rounded to ovoid and 5-8 cm long, with thick, tough scales. They open only slightly at maturity but readily fall to the ground where birds, such as the Clark’s Nutcracker, and squirrels pull the cones apart to access the seeds. Caching of the seeds by these creatures aids in the trees’ germination because the caches are often forgotten.
Named for the smooth white bark on young trunks, whitebark pine is susceptible to both the mountain pine beetle and the fungus white pine blister rust. Efforts are being made to find individuals which have resistance to the blister rust. The species is of conservation concern because, in addition to these attacks, in the absence of forest fires and in a warming climate it can be outcompeted by spruce and fir.
Whitebark pine (Pinus albicaulis), SW Alberta, 2004-08-13. Photo: D. Vujnovic.
Whitebark pine showing foliage and cones, SW Alberta, 2004-08-13. Photo: D. Vujnovic.
Whitebark pine showing 5-needled bundles and mature cone, SW Alberta, 2004-08-13. Photo: D. Vujnovic.
Western white pine (Pinus monticola)
This species is our rarest soft pine, just entering Alberta from B.C. where it is common into the far southwest. Trees are tall, to 50 m, with a possible longevity of 400 years. They occur in a variety of habitats, but particularly in moist valleys and on gentle slopes, usually mixed with other species. The needles are 5-10 cm long, soft and flexible with lines of white stomata. Seed cones are cylindrical.
Eastern white pine (Pinus strobus)
This tree, native to eastern Canada and the northeastern U.S., is the eastern counterpart of western white pine. Growing 30 m tall, it is the tallest tree of eastern Canada and the provincial tree of Ontario. In its native range it occurs on a variety of soils, from sand to peat to rocks. It is widely planted, including in Edmonton area gardens and nurseries, and as a forestry tree.
The needles are 5-15 cm long, flexible, soft, and bluish green, with lines of white stomata. Seed cones are long (8-20 cm) and cylindrical, with thin scales lacking prickles.
It is also susceptible to white pine blister rust, but some control may be achieved by removing its alternate hosts, currants and gooseberries, and by amputating infected branches.
Eastern white pine (Pinus strobus), Killbear Provincial Park, Ontario, 2007-06-09. Photo: P. Cotterill.
Eastern white pine foliage and seed cone from planted tree, Edmonton, 2025-01-06. Photo: P. Cotterill.
Bristlecone pine (Pinus aristata)
This conifer, native to Colorado and adjacent states, may also be grown in some local gardens. It is known for its great longevity: it can live up to 5000 years.
References:
Farrar, John Laird. 1995. Trees in Canada. Fitzhenry & Whiteside Ltd., Ottawa, & Canadian Forest Service.
For more information on conifers, including the production of the complex chemicals that form resin, which is secreted into ducts in many parts of the plant and serves to deter insect predators and seal wounds, see: https://www.thecanadianencyclopedia.ca/en/article/coniferous-trees#:~:text=During%20late%20summer%20and