Montana to the eastern slope of the Cascade Mountains in Washington and Oregon.
In British Columbia it is abundant and large in the Kootenay and Columbia river valleys, reaching as far north as the head of Upper Columbia lake, and attaining its most westerly point, where it was found by Prof. Dawson, in long. 124° E., on a tributary of the Blackwater river. It grows sparingly about the Shuswap lake and in the Coldstream valley near the head of Okanagan lake.
The tree, however, attains its greatest development in Montana, where it is abundant and constitutes a great part of the timber of the Flathead, Lewis and Clarke, and Bitter Root Forest Reserves ; and is met with east of Missoula on the Big Blackfoot river. The tree can be most conveniently seen by the traveller on different points of the Great Northern Railway between Nyack and Bonner’s Ferry. It attains also great perfection in Northern Idaho and North-East Washington, where it constitutes an important part of the timber of the Priest River Forest Reserve. It also occurs in Oregon, in the Blue Mountains, and on the foothills of the eastern side of the Cascade Mountains,’ as far south as Mount Jefferson.
The western larch occurs between 2500 and 6000 feet altitude ; and attains its maximum height and is most abundant in mountain valleys and on alluvial flats, where the average elevation is 3000 to 3500 feet. On the sides of the mountains, owing to the lack of moisture in the soil, it rapidly diminishes in size and vigour. It requires a wetter soil than either Pinus ponderosa or Douglas fir, and is restricted in its distribution where the rainfall is slight.
With regard to the opinion, prevalent even in America, that it grows in a semi- arid climate, my experience is entirely different. The meteorological stations are almost invariably in towns in the prairie regions, where the rainfall is small and trees only occur on the banks of streams; and the maps and statistics of the rainfall give on that account an imperfect picture of the climatic conditions which prevail in the forest regions between the Cascades and the Rocky Mountains. At Kalispell in the Flathead country, which is situated in a treeless plain, surrounded by densely forested mountains, the annual rainfall varies from 13 to 19 inches; whereas at Columbia Falls, placed on the edge of the plain and amidst the larch forests, the rainfall increases to from 20 to 29 inches; and in the mountain valleys, as at Lake Macdonald and Swan Lake, where Thuya plicata attains a large size, the rainfall must exceed 30 inches. The meteorological data of Columbia Falls, which is at 3100 feet elevation, give a fair idea of the climate in which Larix occidentalis thrives, though it is scarcely here at its best. The figures for 1905, which was a dry year, are:—
1 Mr. Cohoon, Forest Assistant in the Northern Division of the Cascade Forest Reserve, wrote to me in 1906 as follows: "The only locality in which larch came under my observation in the reserve was on the east slope of the Cascade Mountains
about 15 miles west of Durfur, Oregon. It did not occur abundantly, but was more or less scattered, in mixture with yellow
pine, red fir, and lodge-pole pine. It was found on moist but well-drained soil at an altitude of about 2500 to 3000 feet.”
He adds that he never saw it west of the summit of the Cascades, which he has travelled over from Columbia river to California.
At Bridal Veil, Oregon, and other places on the Pacific slope, the term larch is erroneously applied to Abies nobilis.
