A Native Tree for You to Love: The American Linden

American linden (Tilia americana), often referred to as basswood, is a stately, deciduous tree native to the eastern United States. A member of the mallow (Malvaceae) family, it is often used in large areas as a shade tree or as a focal point in the landscape. While there has been debate over the years regarding the tree's taxonomy and the number of species, current classification recognizes only one North American native, Tilia americana. Earlier classifications recognized up to fifteen native species and thirteen varieties. That was later changed to three: T. americana, T. caroliniana, and T. heterophylla. However, based on recent studies, there is now a single classification of T. americana,with T. caroliniana and T. heterophylla considered synonyms. Interestingly, taxonomist Carl Linnaeus, who classified the tree in 1753, has a personal connection to the linden tree. His father, Nils Ingemarsson, adopted the surname Linnaeus, derived from the Latin for linden, for the triple-trunked linden tree that was in his childhood village in Sweden.

Legend has it that you could not tell a lie under a linden tree, so trial deliberations and judicial verdicts were rendered under its large canopy. One of the American linden's common names, basswood, is derived from "bastwood", the name early North American settlers gave the tree, referring to its fibrous inner bark, or bast, used to make ropes, nets, mats, shoes, clothing, and thread. Its light, relatively soft wood has been valued for hand carving as well as for use in many instruments, including guitars and percussion instruments. American linden trees have also played a role in Washington, D.C.'s history. As part of the 1874 grounds plan for the 56-acre area surrounding the Capitol building, landscape architect Frederick Law Olmsted oversaw the selection and placement of 1050 trees. Of those original trees, three linden trees still grace the Capitol Square.

Growing 60 to 80 feet tall, American lindens are generally pyramidal when young but will open up slightly as they mature, spreading 30 to 60 feet wide, with low-hanging branches that droop down. Large, dark green, heart-shaped leaves with serrated edges are arranged alternately on the branches. The undersides of the leaves are a dull light green to matte gray. In the fall, the leaves turn pale yellow.

Drooping 5-inch clusters of fragrant, pale yellow flowers (called cymes) bloom in June. These are extremely attractive to bees, giving rise to the nickname "bee tree." When the tree is in full bloom, you may hear buzzing from several feet away. Lightningbugs are another insect drawn to its sweet nectar. These are not all that an American linden tree may attract. It is the larval host plant for eastern tiger swallowtail (Papilio glaucus), red-spotted purple (Limenitis arthemis), and mourning cloak (Nymphalis antiopa) butterflies. Following its flowers, hard, pea-sized nutlets containing 1 to 2 seeds appear, and these are eaten by birds and squirrels.

Hardy in USDA Plant Hardiness Zones 3 to 8, American linden will grow best in full sun to part shade. They prefer moist, well-drained, fertile soil but are adaptable to dry, rocky soils. While they are typically not seriously impacted by insect or disease pests, you may notice Japanese beetles, lace bugs, caterpillars, scale, and boring insects like the linden borer (Saperda vestita). During hot, dry weather, spider mites may do significant damage.

Be sure to use the scientific name when selecting your tree. Other non-native species are hardy in Pennsylvania and may commonly be found in nurseries. These include: big leaf linden (Tilia platyphyllos), Crimean linden (Tilia x euchlora), little-leaf linden (Tilia cordata), and silver linden (Tilia tomentosa).

Carefully consider the tree's placement before planting, as it will be a large tree when mature. There are several cultivars with smaller habits that may be more suitable for smaller landscapes. However, due to their narrow habits, they are less suited as shade trees than the straight species.

• Tilia americana 'Continental Appeal' grows 60 feet tall and 40 feet wide, forming a dense pyramid with large dark leaves with pale undersides.
• Tilia americana American Sentry® grows 60 feet tall and 25 feet wide with a straight, well-formed, narrow, pyramidal canopy.
• Tilia americana Legend® grows 40 feet tall and 30 feet wide with a fast-growing, broadly pyramidal shape with a central leader and better branching than the straight species.
• Tilia americana 'Redmond' grows 35 to 50 feet tall and 25 feet wide with a narrow pyramidal and symmetrical shape.