Tamarack is a distinctive tree species in central Alaska—a conifer that sheds its needles each fall. Tamarack trees usually grow in wet lowland areas (often intermingled with black spruce), and are 9-14 m tall, with rough brown-gray bark. Individuals have a single unbranched trunk with many secondary branches horizontal or sweeping slightly upward. The overall appearance of the tree is conical to slightly pear-shaped. Twigs are light brown with many short spur twigs, covered in leaf scales. Needles are pale blue green, three-angled, 1-2.5 cm long and very narrow, soft, with twelve to twenty radiating out in bundles from short spur twigs. In fall, needles turn golden-yellow before they fall off.
Tamarack produces male and female flowers in different cones, but on the same tree, frequently on the same branches. Male cones are inconspicuous, made up of yellow pollen sacs attached to the side of the leaf-bearing twigs. Female cones are round to ovate, 1-1.5 cm long, with rounded, finely toothed scales, attached on short curved stems. The small seeds are 2-3 mm long, with a slightly winged covering, 4-6 mm. Wood is brown, dense, and highly resin-filled making it rot-resistant.
Tamarack almost never grows in pure stands, with individuals usually found mixed in with black spruce, or sometimes white spruce. Though people unfamiliar with tamarack can mistake it for spruce in summer from a distance, the soft needles arranged in bundles instantly distinguish it from both white (Picea glauca) and black spruce (P. mariana). In winter, needle-less tamarack can be distinguished from dead spruce by the presence of the short spur twigs.
Larix laricina is a deciduous perennial conifer. New needle buds are formed in the fall, green up occurs in spring. In fall, needles turn gold-yellow and are shed from the tree. Cones are produced in early to mid-summer.
Tamarack produces male and female flowers in different cones, but on the same tree, frequently on the same branches. Female cones are grown each year but persist over winter. Male cones are inconspicuous. Wind-dispersed pollen is released in early spring, beginning before budburst but continuing as the leaves grow, and the male cones then are shed. After being fertilized, seeds develop through the summer, and the scales of the female cones open to release the seeds in the fall. The small seeds are wind dispersed. Seeds require a warm, unshaded site to germinate, preferring substrates such as mineral soil and feathermoss mats (Brown et al. 1988).
Throughout central Alaska, swathes of tamarack have died due to heavy defoliation by larch sawflies Pristiphora erichsonii in the 1990s (Holsten and Burnside 1997). In Denali National Park, 60% of standing trees are dead (Roland et al. 2013). Other insects that utilize L. laricina include (but are not limited to): larch budworm Zeiraphera spp. and the larch bark beetle (Dendroctonus simplex).
The slow-decaying wood of tamarack is sometimes used for lumber.
Larix laricina is a boreal North American endemic species, occurring in all Canadian provinces, and ranging south into the upper Midwest, mid-Atlantic and New England. This species is restricted to the interior of Alaska, disjunct from the broader boreal distribution in North America. In Alaska, L. laricina occurs from Aniak to south of Fairbanks, west to Denali and east to Delta Junction. In Denali, it occurs in scattered sites across the northwestern lowlands. The Alaskan population of L. laricina has sometimes been treated as a separate species or subspecies.
Of the tree species in the Park, tamarack is the least likely to be found at high elevations. Most occurrences were below 300 m. trees were primarily found on low slopes (<4 degrees) with the average site at an angle of 1.78 degrees. However, there is an unexpected uptick in occurrences at slopes of 20-28 degrees, and this is where this species reaches its highest degree of cover (0.5%, lowest of the tree species). Tamarack grows on all aspects, with a slight decrease in occurrences on south facing slopes.
Tamarack is found almost exclusively in acidic wetlands, or in wet, cold mineral soils in uplands. Its presence is correlated with shallow active layer (permafrost) and a deep soil organic layer (Roland et al. 2013).