Climatic conditions associated with the species range are generally continental-cold winters, warm summers, and a humid to subhumid moisture regime. Mean annual precipitation within the species range is 530 min (21 in) at the western limit and 1140 min (45 in) in the northeast. The northern limit of basswood approximates the - 18° to -17° C (0° to 2° F) isotherm for mean daily minimum January temperature. Basswood reaches its maximum development in areas averaging 18° to 27° C (65° to 80° F) in July and receiving 250 to 380 mm (10 to 15 in) of precipitation during the growing season. The frost-free growing period varies from 80 to 180 days within its range.

Soils and Topography
Studies relating to the presence of basswood to soil characteristics in Minnesota, Wisconsin, and Michigan indicate that stands in which basswood shared dominance were generally confined to sandy loams, loams, or silt loams, with basswood obtaining maximum development on the finer textured soils. Most soils were classified as Hapludalfs within the Alfisols order, although some Eutrochrepts (Inceptisols), Cryandepts (Inceptisols), mesic families of entic Fragiorthods (Spodosols), and Haplorthods (Spodosols) were noted. Basswood grows best on mesic sites, but it is also found on coarse soils such as the sand dunes near Lake Michigan and on dry, exposed rock ridges in Ontario and Quebec.

The species grows on soils ranging in pH from 4.5 to 7.5 but occurs more often in the less acidic to slightly basic part of this range. In fact, calcareous soils have been associated with the presence of basswood. The importance of aspect and edaphic factors to local distribution is reflected by the restriction of basswood throughout much of its range to moist sites on north- and east-facing slopes. Maple-basswood forests in southern Wisconsin are largely restricted to northerly exposures. Basswood is restricted to more mesic sites in southern Illinois and in northern Kentucky. At the western limit of its range, basswood frequently grows on the eastern side of lakes and along major drainages. This localized growth is often ascribed to fire protection. although lack of fire may be a reason for the persistence of a fire-sensitive species such as basswood, presence and distribution are controlled more by soil moisture and the ameliorating effects of water on the local climate. Basswood is classified as a nitrogen-demanding species because it grows poorly on sites deficient in nitrogen. With increasing nitrogen supplies, basswood growth increases markedly, approaching a maximum radial increment when 560 to 670 kg/ha (500 to 600 lb/acre) of nitrogen are added.

Basswood leaves have high contents of nitrogen, calcium, magnesium, and potassium at the time of leaf fall and they contribute most of these nutrients to the forest floor. Associated Forest Cover American basswood grows in mixture with other species and only rarely forms pure stands. It is dominant in a single forest type, Sugar Maple-Basswood (Society of American Foresters Type 26). This cover type is most common in central Minnesota and western Wisconsin but is represented elsewhere from central Illinois, northward to southern Ontario and Quebec, eastward to northwestern Ohio, and westward along valley slopes of the prairie forest transition (15). Sugar maple (Acer saccharum) dominates both overstory and understory layers, with basswood achieving the position of second dominant in the tree layer. Common associates are white ash (Fraxinus americana), northern red oak (Quercus rubra), eastern hophornbeam (Ostrya virginiana), red maple (Acer rubrum), and American elm.

Flowering and Fruiting- The fragrant, yellow-white, flowers are borne on loose cymes on long stalks attached to leafy bracts. Flowering generally occurs in June but can begin in late May or early July, depending on latitude and annual variations in temperature. Flowering follows initial leaf-out and lasts approximately 2 weeks. During this period, all stages of floral development are present on a single tree or even in a single inflorescence (4 to 40 flowers per inflorescence). The flowers attract a number of insect pollinators. In a study of the pollination biology, 66 species of insects from 29 families were identified as pollinators of the  flowers.

Bees and flies were the most common diurnal pollinators; moths were the primary nocturnal visitors. The fruit, a nutlike drupe 5 to 10 mm (0.2 to 0.4 in) in diameter, usually contains one seed but in collections from both open- and forest-grown trees, 12 percent of the fruit contained two seeds and less than 1 percent contained three seeds. The seeds have a  crustaceous seed coat (testa), a fleshy yellowish endosperm, and a well-developed embryo. A variety of forms of fruit and seed have been noted, including egg-shaped, round, onion-shaped, conical, and pentagonal. Individual trees tend to consistently produce fruit of a particular form and size.

Basswood seeds are eaten by mice, squirrels, and chipmunks, thus reducing the chances of seedling establishment. Many different insects attack basswood, but few serious insect problems exist. The linden borer (Saperda vestita) makes long, irregular tunnels, particularly at the base of the tree, and may damage weak, very young, or very old trees. Local infestations of defoliators may occur. The primary ones include the linden looper (Erannis tiliaria), basswood leafminer (Baliosus nervosus), spring cankerworm (Paleacrita vernata), fall cankerworm (Alsophila pometaria), whitemarked tussock moth (Orgyia leucostigma), gypsy moth (Lymantria dispar), and forest tent caterpillar (Malacosoma disstria). In New England, American basswood is a highly preferred host for gypsy moth, while in southern Quebec, it was classified as intermediate in susceptibility to gypsy moth defoliation.

Special Uses - Basswood has relatively soft wood that works exceptionally well and is valued for hand carving and has many other uses including cooperage, boxes, veneer, excelsior, and pulp. Basswood is economically important for timber, especially in the Great Lakes States. The inner bark, or bast, can be used as a source of fiber for making rope or for weaving such items as baskets and mats. Basswood flowers produce an abundance of nectar from which choice honey is made. In fact, in some parts of its range basswood is known as the bee-tree. Throughout the Eastern United States, basswood is frequently planted along city streets.
--USDA Forest Service Silvics Manual

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