By Patsy Cotterill
The onset of autumn and a misidentification in a draft version of the October WN got me thinking that larches might make a good subject for the next newsletter. Larch trees attract attention when they show the first hint of yellowing, which turns to glowing golden in full sunlight, and finally to muted ochre as the needles drop off and the cloak of foliage thins to a mere veil. Larches (genus Larix in the pine family, Pinaceae) are unusual in being deciduous conifers. This is in contrast to our pines, firs and spruces which retain their needles for several seasons and so appear evergreen (although I could swear that the white spruce in my back garden thinks it is a larch, so heavily does it prune its dead leaves in the fall!).
Larch species are adapted to the cold, moist regions of the Northern Hemisphere, and are found in the boreal forests of Eurasia and North America, as well as in mountain habitats. Their leaves are soft, flexible and needle-like, attached singly on shoots of the current year but otherwise produced in clusters of 10-40 leaves on short, woody, spur shoots along the branches. (In contrast, spruces and firs have leaves attached singly along the twigs, and pines have two, three or five, much longer leaves attached at the base to form a bundle.) Male and female larch cones occur on the same individual tree and usually on the same branches; the male cones bearing the stamens are small, yellowish and round, and fall off after pollination. The female cones are larger, woody but more flexible than those of pines, and have thin bracts attached at their base. They remain on the tree for several years. The seeds have papery wings promoting wind dispersal and are usually borne in pairs on the inside of the cone scales.
There are three native larches in Canada, all of which occur in Alberta. Tamarack (Larix laricina) is widespread across the country in boreal habitats. Locally, it occurs in pockets of our peaty soils, which often represent little islands of boreal forest, such as at Wagner Natural Area, and in the wetlands between the sand dunes, for example, at Bunchberry Meadows Conservation Area. Subalpine larch (L. lyallii) and western larch (L. occidentalis) are restricted to B.C. and Alberta and, as their names suggest, are mountain species, with western larch being quite rare in Alberta and much more common in B.C. For mountaineers, these two species can be distinguished by somewhat subtle characteristics as well as habitat: subalpine larch, which occurs only at high altitudes, generally has needles that are four-angled compared to western larch’s triangular ones, and its twigs are woolly; moreover, its bracts are obviously longer than the scales and have bent tips, whereas in western larch, which occurs at lower altitudes on mountain slopes, the bracts only slightly exceed the cone scales.
Tamarack grows 15-25 m tall, and has a grey bark, scaly in older trees, similar to that of spruce. Trees are generally considered to live for about 150 years, but gnarled, stunted trees at Wagner Natural Area have been dated as over 300 years old. Seed cones are 1-2 cm long, elongate and purple when young, but becoming more ovoid and light brown by the time the cones open in mid-August to release the seeds. Old cones with open cone scales are dark brown. As shallow-rooted trees tamaracks are prone to damage by wind and flooding. As a widespread species they are host to a variety of insect predators and to fungal diseases.
Unfortunately, porcupines much prefer the inner bark of tamarack to that of spruce, resulting in the killing of fine, mature trees. Snowshoe hares eat the seedlings and red squirrels eat the seeds. The dense, outspreading branches provide plenty of nesting sites for birds. Indigenous peoples used tamarack for making snowshoes and a variety of medicinal purposes. Interestingly, early surveyors used tamarack posts to mark the northeast corner of sections within townships: the wood was light to carry but hard and extremely rot-resistant. Ornamentally, tamarack is often used for bonsai.
In peaty soils in our region, tamarack usually grows in the company of black spruce, as is the case in Wagner Natural Area, its feathery-looking foliage and shape allowing it to be easily distinguished from the dark green, rigid spires of spruce in the summer and by its leaflessness in winter. But in Bunchberry Meadows black spruce is rare, and tamaracks alone fringe the edges of several wetlands. In one area on the western side of the site tamarack occurs in dense stands of similar-aged trees, lacking understory vegetation under heavy needle litter and inviting speculation as to how the stand got established. Since tamarack is a pioneering tree which likes open areas and plenty of sunlight, opening up some of these stands by cutting might result in trees of better form and possibly even in seedling regeneration.
You don’t need to get your feet wet, however, to enjoy the seasonally changing foliage of larches. The non-native Siberian larch (L. sibirica) is commonly planted in Edmonton, in gardens, grounds and parks, where there is room for its spreading branches which reach almost to the ground. A native of western Russia and Siberia, where it is a major forest tree, this species is well adapted to dry, cold continental winters.
Three other non-native larches, European larch, Japanese larch, and Dahurian larch are also planted in Canada, but I do not know if they are grown in Edmonton.
Sources:
Farrar, John Laird. 1995. Trees in Canada. Ottawa, ON. Fitzhenry & Whiteside Ltd. & Canadian Forest Service, Natural Resources Canada.
Moss, E.H. 1983. Flora of Alberta, 2d ed. rev. by J.G. Packer. University of Toronto Press, Toronto.