adapted to heat and humidity and will perform poorly in a hot climate. The tree attains its greatest longevity and growth potential in Zones 3–4. Soils White spruce occurs on a wide variety of soils, including soils of glacial, lacustrine, marine, and alluvial origins; overlying basic dolomites, limestones and acidic Precambrian and Devonian granites and gneisses; and Silurian sedimentary schists, shales, slates, and conglomerates. The wide range of textures accommodated includes clays, even those that are massive when wet and columnar when dry, sand flats, and coarse soils. Its occurrence on some organic soils is not characteristic, except perhaps on shallow mesic organic soils in Saskatchewan and in association with black spruce on organic soils in central Yukon. Podzolized, brunisolic, luvisolic, gleysolic, and regosolic (immature) soils are typical of those supporting white spruce throughout the range of the species. Soils supporting white spruce are most commonly Alfisols or Inceptisols. In the podzol region of Wisconsin, white spruce occurs on loam podzols, podzolized gley loams, strongly podzolized clays, gley-podzol clays, stream-bottom soils, and wood peat. Moist sandy loams also support good growth. On sandy podzols, it is usually a minor species. Good development occurs on moist alluvium on the banks of streams and borders of swamps. White spruce makes good growth on well-drained lacustrine soils in Alberta Mixedwoods, on moderately-well-drained clay loams in Saskatchewan,, and on melanized loams and clays (with sparse litter and a dark-coloured organically-enriched mineral horizon) in the Algoma district of Ontario. White spruce becomes less accommodating of soil with increasing severity of climate. The distribution of white spruce in Labrador seems to depend almost entirely on the character of the soil, and between the southwestern shores of Hudson Bay and the northeastern regions of Saskatchewan, white spruce is confined to very local physiographic features, characterized by well-drained or fertile soils. On dry, deep, outwash deposits in northern Ontario, both white spruce and aspen grow slowly. But, broadly, white spruce is able to tolerate considerable droughtiness of sites that are fertile, and no fertile site is too moist unless soil moisture is stagnant. Soil fertility holds the key not just to white spruce growth but to the distribution of the species. At least moderate fertility is needed for good growth, but white spruce occurs on many sites where nutrient deficiencies depress its growth more than that of black spruce, red spruce, Norway spruce, and the pines generally. Minimum