to 70 m tall. Foliage strongly flattened on all shoots. Cones slightly narrower (mostly less than 4 cm broad), with thinner, fairly flexible scales. Tolerates winter temperatures down to about -25° to -30 °C; growth on good sites may exceed 1.5 m per year when young. Abies grandis var. idahoensis. Interior grand fir. Interior forests, at (600–) 900–1800 m altitude, on the east slope of the Cascades in Washington and northern Oregon and in the Rocky Mountains from southeast British Columbia south to central Idaho, northeast Oregon and western Montana. A smaller, slow-growing tree to 40–45 m tall. Foliage not strongly flattened on all shoots, the leaves often raised above the shoot, particularly on upper crown shoots. Cones slightly stouter (mostly over 4 cm broad), with thicker, slightly woody scales. Tolerates winter temperatures down to about -40 °C; growth on good sites not exceeding 0.6 m per year even when young. Grand fir is very closely related to white fir, with the interior variety idahoensis particularly similar to the western forms of white fir from western Oregon and California, intergrading with it where they meet in the Cascades of central Oregon. Taxonomy The species was first described by Scottish botanical explorer David Douglas, who in 1830 brought its seeds back to Britain; in 1831 he described specimens he had collected along the Columbia River in the Pacific Northwest. Distribution and ecology The grand fir grows along the coast from southwest British Columbia to Northern California, with the inland variety growing in eastern areas of Washington and Oregon, and the Idaho Panhandle. It can be found growing at elevations of up to . Habitats typically receive at least of annual rainfall, but are still too dry or outside the range of more shade-tolerant competitors like western hemlock and western redcedar. Along with the closely related white fir, grand fir is more shade tolerant than Douglas-fir. Due to wildfire suppression, grand fir was able to proliferate in areas previously dominated by the relatively fire-resistant inland Douglas fir, ponderosa pine, and western larch. The lack of smaller fires allows both grand and white fir saplings to form a fuel ladder, enabling crown fires. Grand fir's bark is thinner than that of white fir, making the former species more susceptible to threats like fire and rot. Specimens have historically been able to live up to nearly 300 years, but in modern stressed conditions, 100