Basswood, also known as American Linden, is a large native North American tree that can grow more than 80 feet tall. In addition to being a majestic tree in the landscape, basswood is a soft, light wood and prized for hand carvings and making baskets. Native American basswood is found on rich, wet soils of the central and eastern United States. In the landscape, is a very beautiful and large tree with a majestic oval canopy mounted on a tall, straight trunk. Mid-summer brings abundant clusters of aromatic, yellow blooms which attract bees who make a prized honey – the tree is often fondly called the honey or bee tree.
I. Appearance and Characteristics
Tilia americana is a species of tree in the family Malvaceae, native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Oklahoma, southeast to South Carolina, and west along the Niobrara River to Cherry County, Nebraska. It is the sole representative of its genus in the Western Hemisphere, assuming T. caroliniana is treated as a subspecies or local ecotype of T. americana. Common names include American basswood and American linden.
The American basswood is a medium-sized to large deciduous tree reaching a height of 18 to 37 m (60 to 120 ft) exceptionally 39 m (128 ft) with a trunk diameter of 1–1.5 m (3–5 ft) at maturity. It grows faster than many North American hardwoods, often twice the annual growth rate of American beech and many birch species. Life expectancy is around 200 years, with flowering and seeding generally occurring between 15 and 100 years, though occasionally seed production may start as early as eight years.
The crown is domed, the branches spreading, often pendulous. The bark is gray to light brown, with narrow, well defined fissures. The roots are large, deep, and spreading. The twigs are smooth, reddish-green, becoming light gray in their second year, finally dark brown or brownish gray, marked with dark wart-like excrescences. The winter buds are stout, ovate-acute, smooth, deep red, with two bud scales visible.
The leaves are simple, alternately arranged, ovate to cordate, asymmetrical, unequal at the base (the side nearest the branch the largest), 10–15 cm (4–6 in) (can grow up to 25 cm or 10 in) long and broad, with a long, slender petiole, a coarsely serrated margin and an acuminate apex. Bean noted that occasionally, enormous leaves measuring 38 cm or 15 in long by 25 cm or 10 in wide appear on thick, succulent shoots. They open from the bud conduplicate, pale green, downy; when full grown are dark green, smooth, shining above, paler beneath, with tufts of rusty brown hairs in the axils of the primary veins; the small stipules fall soon after leaf opening. The fall color is yellow-green to yellow. Both the twigs and leaves contain mucilaginous sap.
The flowers are small, fragrant, yellowish-white, 10–14 mm (13⁄32–9⁄16 inch) in diameter, arranged in drooping, cymose clusters of 6–20 with a whitish-green leaf-like bract attached for half its length at the base of the cyme. They are perfect, regular, with five sepals and petals, numerous stamens, and a five-celled superior ovary. The leaves emerge in mid-spring, but the flowers require day lengths of approximately 14 hours and 30 minutes to form, hence T. americana’s range is limited to north of the 35th parallel. Time of flowering varies by several weeks depending on the latitude; early May in Canada and early June in the extreme southern extent. Leaf drop in fall occurs between early and late October depending on the latitude. The flowers are fragrant and insect-pollinated.
The fruit is a small, globose, downy, hard and dry cream-colored nutlet with a diameter of 8–10 mm (5⁄16–13⁄32 in).
II. How to Grow and Care
Sunlight
American basswood trees like plenty of sunlight and ideally should receive 3-6 hours of light per day. You can plant it somewhere outdoors with sufficient sunlight, such as the sunny side of a house. Sufficient sunlight promotes tree photosynthesis and is conducive to its growth. American basswood can also grow normally in partial shade, but too little light will reduce the number of flowers or even prevent blooming. Seedlings and saplings are more shade-tolerant. You can add a shade net in summer to protect small trees from too-strong light.
Temperature
American basswood trees prefer to live in a mild, moist environment and are very cold-hardy. The tree needs to be kept well-hydrated in moist soil for growth. However, it does not tolerate waterlogging. If living in standing water for a long time, the tree can lose leaves or its roots can rot. It will also grow poorly in arid and swampy areas.
Watering
American basswood does not tolerate drought and prefers moist soil, but also does not like stagnant water. In early spring when there is little rain, dry weather, and strong transpiration, you should provide the tree with more water. During the rainy season, you should stop watering. In the early flowering, late flowering, and fruiting periods, make sure to give it enough water. At the beginning of winter, water thoroughly once and then stop to promote lateral growth and lignification.
American basswood has a deep root system and generally does not need watering after maturing. However, it will need more water if it encounters a long-term drought. If the soil dries out easily, you can spread an organic mulch on the surface. This reduces evaporation and keeps the soil moist.
Soil
American basswood has a deep and wide root system and grows best in deep, fertile, well-drained soil. The trees will not grow well in poor soils or waterlogged, non-aerated, clay soils. If the soil is clay-like, add coarse sand to improve its water permeability. The tree prefers alkaline to neutral soils, and can also grow in slightly acidic soils. However, it cannot grow in marshes or saline soils.
Fertilizing
Mix organic or slow-release fertilizer with the soil before planting, and apply nitrogen fertilizer every 20 days after transplanting until early fall. You do not need to apply very much fertilizer each time – just spread it evenly. Mature trees demand less fertilizing, so you can follow up with some phosphorus and potassium fertilizer depending on the tree’s situation to promote the growth of the branches and leaves and improve the plant’s resistance. If the soil is fertile, no fertilization may be necessary.
Planting Instructions
You can buy american basswood seedlings at a garden center. If transplanting the seedlings is necessary, do it in early spring, as this is when they are ready to germinate and grow and the roots can also easily heal and regenerate. After a period of normal growth from early spring to late fall, the tree will have recovered from any transplanting injuries and be prepared for overwintering.
It is best to plant american basswood in the sun, in a 50 to 60 cm deep hole, with sufficient base fertilizer. After planting young trees, fill in the soil and compact it, or create a 10 cm-high soil mound at the bottom of the trunk to keep the soil around the young trees moist and warm. Then, water the tree thoroughly and follow up often to always keep the soil moist. You can also use sticks and iron frames to support the tree in case the wind threatens to blow it down.
Pruning
To keep the American basswood trunk straight, start cutting lateral branches and one-third of the branches growing upward during the first winter or the spring of the second year after planting. Stop when the trunk height reaches 5 to 6 m. Every spring, completely cut off new shoots and branches that sprout near the ground on the trunk as early as possible.
Otherwise, these buds can consume too many nutrients and negatively affect trunk growth.
To shape the canopy nicely, prune the trees in winter. Cut overgrown lateral branches, thin the overcrowded branches, and completely cut off diseased and dry branches. To control the overgrowth of lateral branches growing to 20 cm, remove their top buds in early summer.
Transplanting
The prime time to transplant american basswood is from late spring to midsummer, as it allows the plant ample time to establish itself before winter. Choose a location with fertile, well-draining soil, and partial to full sunlight. For a successful transplant, water the american basswood thoroughly before and after moving it, and monitor its progress closely.
Pests and Diseases
Insects such as aphids, Japanese beetle, and linden beetle all pose potential threats to the foliage of the tree, but these are cosmetic issues and are not a fungal threat. Fungal problems such as anthracnose and Verticillium wilt can cause issues in American basswood such as causing leaves and twigs to die off. Pruning off dead twigs and leaves will help minimize the effects from these fungal problems.
III. Uses and Benefits
- Wood
The wood is pale brown, sometimes nearly white or faintly tinged with red; light, soft with fine close grain; clear of knots but does not split easily. It is low in strength and has a poor steam-bending classification. It can take stains and polish without difficulty and it planes, glues, screws and nails well. It is sold generally under the name basswood. It has a density of 0.4525 (relative to water). The wood is considered odorless. This makes it valuable in the manufacture of wooden utensils and furniture. It is also used for woodcarving. The inner bark is very tough and fibrous, used in the past for making ropes.
Basswood is a tonewood commonly used in the manufacture of solid-body electric guitars. It is relatively lightweight and easy to work and sand. It accepts paint and finishes very well. It is usually used for guitars that will be painted an opaque color as its lack of notable grain makes it an unattractive candidate for transparent finish. It exhibits a very balanced, even tone with a good low/mid-mid range projection making it suitable for a wide variety of musical applications. It is often paired with maple laminates to balance the midrange with more treble (inherent to maple) to make a very well rounded sounding instrument. It is also relatively inexpensive, which has made it a favorite of large factories mass-producing instruments.
It has proven especially popular in instruments made for musicians who play heavy metal. This could be because its tonality helps level out the thin, tinny sound associated with knife edged tremolo contacts that many modern rock and metal players use as bridges on their guitars.
- Medicinal uses
Although Tilia cordata is believed to be stronger, T. americana is also used medicinally. The dried flowers are mildly sweet and sticky, and the fruit is somewhat sweet and mucilaginous. Linden tea has a pleasing taste, due to the aromatic volatile oil found in the flowers. The flowers, leaves, wood, and charcoal (obtained from the wood) are used for medicinal purposes. Active ingredients in the linden flowers include flavonoids (which act as antioxidants), volatile oils, and mucilaginous constituents (which soothe and reduce inflammation). The plant also contains tannins that can act as an astringent.
Linden flowers are used in colds, cough, fever, infections, inflammation, high blood pressure, headache (particularly migraine), as a diuretic (increases urine production), antispasmodic (reduces smooth muscle spasm along the digestive tract), and sedative. The flowers were added to baths to quell hysteria, and steeped as a tea to relieve anxiety-related indigestion, irregular heartbeat, and vomiting. The leaves are used to promote sweating to reduce fevers. The wood is used for liver and gallbladder disorders and cellulitis (inflammation of the skin and surrounding soft tissue). The wood burned to charcoal is ingested to treat intestinal disorders and used topically to treat edema or infection, such as cellulitis or ulcers of the lower leg.
Several animal studies showed that the extract of T. americana increased sleeping time by 50 minutes (similar to the effects of diazepam) and decreased movement, which indicates sedative effects. It is argued that its mechanism of action is due to the flavonoid quercetin, as it inhibits the release of histamine.
- Other uses
The American basswood is recommended as an ornamental tree when the mass of foliage or a deep shade is desired; no native tree surpasses it in this respect.
The foliage and flowers are both edible, though the tender young leaves are more palatable. It is a beneficial species for attracting pollinators as well. Bees produce excellent honey with a mildly spicy flavor from its blossoms.
