Larix occidentalis Nutt.

The tallest-growing member of the genus, Larix occidentalis reaches heights in excess of 60 m in native forests in the American northwest. The tallest accurately measured in modern times was just shy of 65 m, in Okanogan-Wenatchee National Forest, Washington; the trunks can also become massive, with one measured at 1.94 m dbh (52 m tall) near Bridesville, British Columbia (Earle 2026). There are several reliable records of long-lived trees, too, including 824 and 920 years in Oregon and Montana respectively. Like all larches this species has long been prized for its excellent timber, and it is likely that even taller and larger and perhaps older trees grew in forests that were cut long ago (Earle 2026).

One remarkable feature of this larch is its architecture. Despite being the tallest-growing species, and capable of developing very wide trunks, the first-order branches are relatively short, and in closely-grown trees and natural stands incredibly so. Writing over a century ago Charles Sargent remarked ‘there is certainly no other instance among the trees of the northern hemisphere where such massive trunks support such small, short branches and sparse foliage’ (Sargent in Elwes & Henry 1906–1913). One could of course argue that Picea omorika had not yet been discovered, but its trunks do not become nearly so massive as those of Larix occidentalis, and even after the exploration of so many other rich floras through the 20th century – China leaps to the front of the imagination – one is rather forced to admit that Sargent’s assertion has stood the test of time.

A pioneer species that quickly develops thick, fire-resistant bark, Larix occidentalis soon sheds its lower branches, helping to protect the crowns from the fires that should be a natural – and important – component of this ecosystem. In some areas, fire suppression has historically disadvantaged larch which would naturally seed into gaps created by fire, but suppression regimes meant that some stands were overtaken by secondary-succession species. In some protected areas work is ongoing to restore these natural systems, but of course extensive areas of forest are preferentially managed for the larch which is an important timber crop.

Larix occidentalis was discovered for modern botany by the Lewis and Clark Expedition in 1805–06. David Douglas found it later in Oregon in 1826 but did not collect seed, having mistaken it for the European species L. decidua; although he collected specimens for the herbarium it seems that nobody at Kew scrutinised them too closely. It would not be described to science until 1846, and then by Thomas Nuttall, who had found it in Oregon’s Blue Mountains in 1834 (Kent 1900). Introduction to cultivation would have to wait until 1881 when the Arnold Arboretum procured seed from Oregon, but the maritime-continental Boston climate did not suit it and young plants failed to thrive on their own roots, only performing better when grafted onto L. kaempferi rootstocks; the best of these was 10 m tall when observed by Henry Elwes in 1906 (Elwes & Henry 1906–1913). The Arnold sent forty seedlings to Kew in 1881. These were grown on and planted out in 1889, and while a few survived and became respectable specimens mostly they failed. A 1903 introduction from Idaho actually performed better at Kew, somewhat contrary to what would normally be expected from a northwest American tree distributed on both sides of the continental divide. After this there appears to have been a gap of some years before a series of reasonably frequent re-introductions commenced during the 1920s.

Of the 1881 introduction to Kew, one possible survivor was 25.5 m tall × 52 cm dbh in 2022 (accession 1969.10625, although this may have been from the 1903 Idaho sending); another tree known with certainty to be from the 1881 introduction (1969.10626) was 20 m × 38 cm at Kew in 2022. Two trees in Scotland from the Idaho sending are at Dawyck (19795004*A), 26 m × 55 cm in 2025, and at the Royal Botanic Garden Edinburgh (19090018*A, pictured below), 22.3 m × 55 cm in 2025. The tallest on record in the UK is one in the Clinton-Baker pinetum at Bayfordbury, Hertfordshire, 34.5 m × 64 cm in 2014, but its origin is unknown (The Tree Register 2026). Like most larches in UK cultivation Larix occidentalis seems to grow very rapidly in youth, but slows right down after several decades; it is not especially long-lived (Mitchell 1972).

Records from other European nations are incredibly scant, but it must be cultivated here and could perhaps be expected to perform a little better in the climate of western mainland Europe than in the UK and Ireland. It is recorded from Hørsholm in Denmark (University of Copenhagen 2026), and Arboretum van Tervuren in Belgium where a tree was 37 m × 52 cm in 2022 (Beltrees 2025).