Western larch occurs in the Northern Rockies Ecoregion and in the northeast portion of the Middle Rockies Ecoregion. It is very intolerant of shade but highly tolerant of fire. Historically it occurred as the predominant species on sites where mixed severity fires killed the thinner barked species.
The amount of western larch cover type has decreased by 72 percent since the mid 1950’s. It has been replaced largely by Douglas-fir and grand fir, species that are more susceptible to fire, drought, insects and disease.
Western larch has few serious insects and diseases, and the most significant impacts have come from management practices that favored shade tolerant species. These include selectively logging of the more valuable big larch; lack of regeneration harvesting or fire; and a lack of thinning, either mechanical or fire induced.
The largest of the nine larch or tamarack species growing in the Pacific Northwest, the western has pale green foliage, a rather “feathery” graceful arrangement of branches, and an open crown. Brilliant yellow in late fall, the needles drop in November. In fact, this species is one of only two coniferous species that sheds its needles every fall. Its thick bark is reddish-brown in color and features elongated scale plates.
Western larches can grow to heights of 200 feet and to diameters of 7 feet, though more common examples are in the range of 150 high and 4 feet in diameter. The crown of the western larch generally comprises only one-third to one-half its total height, and mature trees often have 60 to 100 feet of clear trunk.
A fire-resistant species, western larch occupies a restricted range, preferring moist mountain slopes from 2,000 to 7,000 feet in elevation. Western larch is generally found in mixed-conifer stands, where it competes aggressively with other species that prefer full sunlight.
An important timber species, western larch wood is used in applications where its strength and decay resistance are particularly useful, such as in mine framing, telephone poles, and railroad ties.