Linden tree guide: American basswood, littleleaf linden and how to grow them

At a glance

What a linden tree is

Linden is the common name for trees in the genus Tilia, now placed in the mallow family (Malvaceae; older references use Tiliaceae). The same trees go by different names depending on where you are: basswood in North America, usually meaning the native American basswood (Tilia americana), and lime in Britain and Europe, which has nothing to do with citrus limes.

Lindens are large shade trees with heart-shaped leaves and clusters of small, intensely fragrant, cream to pale yellow flowers in early summer. The flowers hang from a distinctive narrow, papery, leaf-like bract, and the small, hard nutlets that follow stay attached to it. Lindens are heavily visited by bees when in bloom, and the Morton Arboretum notes that littleleaf linden's ability to withstand polluted environments makes it a common choice for lawns and parkways in urban settings.

Linden vs basswood

They are the same genus. "Basswood" usually refers to the native American species, T. americana, and to its pale, soft lumber; "linden" is the general name for any Tilia and the name nurseries use for landscape species and cultivars, including American linden. "Lime" or "lime tree" is the British name for the same genus.

How to identify a linden tree

• Leaves: alternate, simple, heart-shaped with a pointed tip, a toothed edge and a noticeably lopsided base (one side of the leaf meets the stalk higher than the other). Size depends on species: American basswood leaves are about 3 to 6 inches long (Iowa State University Extension), while littleleaf linden's shiny dark green leaves are much smaller.
• Flowers: small, pale yellow, very fragrant, in drooping clusters in early summer, each cluster attached partway along a narrow, papery bract up to about 5 inches long (Missouri Botanical Garden).
• Fruit: an open cluster of small, hard nutlets hanging from the same bract, which acts as a wing; Iowa State lists seed dispersal in September and October.
• Bark: light or silvery gray and smooth to finely ridged on young trunks; older trunks break into long ridges and furrows, dark gray to almost black (Iowa State University Extension).
• Twigs and buds: light brown to gray twigs with prominent, plump, bluntly pointed, dark red buds.
• Sprouts: American basswood sprouts readily from the base of the trunk, forming characteristic clumps of several stems, per Iowa State University Extension.

In winter, bark and buds carry the identification; see how to identify a tree by bark.

Types of linden trees

American basswood (Tilia americana)

The native species, a large tree of moist woods and slopes across eastern North America. Iowa State University Extension calls it the favorite tree of honeybees and beekeepers, notes that its honey is sometimes sold separately as basswood honey, and explains that the name comes from "bast": the tough, fibrous inner bark that Native Americans used for cords and ropes. Missouri Botanical Garden lists it for full sun to part shade in average, medium-moisture, well-drained soils, but describes it as generally intolerant of air pollution and urban conditions.

Littleleaf linden (Tilia cordata)

A European species with a dense, low-branched, pyramidal to ovate crown, per Michigan State University Extension. The Morton Arboretum and MSU both describe it as tolerant of urban conditions, which is why it is so common along streets and parkways. 'Greenspire' is a widely grown cultivar that MSU describes as having a strong central leader and symmetrical branching; Utah State University Extension lists it at 40 to 60 feet tall and 35 to 50 feet wide.

Silver linden (Tilia tomentosa)

Recognized by leaves that flash silvery-white underneath in the wind. Oklahoma State University's Oklahoma Proven program describes it as more heat tolerant than other lindens and quite tolerant of high-pH soils and urban conditions, and lists its fragrant flowers in late June to July, later than the June bloom Missouri Botanical Garden gives for American linden. That late bloom matters for bees (see below).

American linden vs littleleaf linden

The quick difference: American linden is native, larger-leaved and suited to bigger, naturalistic sites, but Missouri Botanical Garden notes it is generally intolerant of city conditions and suggests European lindens for urban areas; littleleaf linden is European, small-leaved, denser and more formal, and better adapted to street and urban use.

Where lindens grow well

American basswood is native from Quebec to southeastern Manitoba and far eastern North Dakota, south to Oklahoma, Tennessee and North Carolina, per Missouri Botanical Garden, and prefers moist, fertile, well-drained loams. As landscape trees, lindens grow across much of the northern and central United States, roughly USDA zones 2 to 8 depending on species.

Planting and care

1. Choose the species for the site: American linden for large, naturalistic spaces; littleleaf for formal or urban settings; silver linden for hotter, drier regions.
2. Plant in spring or fall with the root flare at grade; follow how to plant a tree.
3. Allow for the mature crown. American basswood can spread 30 to 50 feet; keep it clear of overhead wires and away from where you park.
4. Water through establishment and during drought; lindens prefer consistently moist soil.
5. Prune in the dormant season to keep a single leader, and remove basal sprouts on American lindens regularly if you want a single trunk (removing tree suckers).

Litter, honeydew and siting

Are linden trees messy? Moderately, and mostly in summer. Expect three kinds of mess:

• Honeydew from linden aphids. Washington State University's HortSense notes that lindens planted along streets and in parking lots are commonly infested with linden aphids, which feed in colonies on leaf undersides and produce large amounts of sticky honeydew that lands on cars, patio furniture and paving below. Black sooty mold can then grow on it. WSU says the honeydew is a nuisance but does not harm the tree. See sticky residue on leaves.
• Flower and bract drop after bloom, and fruit clusters with their bracts in fall and winter.
• Basal sprouts on American linden.

The practical rule: do not plant a linden over a driveway, parking area, deck or patio where honeydew would be a nuisance. Compared with sweet gum's gumballs or cottonwood cotton, linden litter is lighter and seasonal. University of Tennessee Extension's guide to "sewer-safer" trees lists basswood (Tilia) among the large trees not recommended near wastewater pipes and advises keeping any tree more than 10 feet from sewer lines; otherwise, site lindens for the full mature crown.

Lindens and bees

Linden flowers draw bees in large numbers; Missouri Botanical Garden notes that a tree in full bloom can be heard humming many feet away, and Iowa State University Extension calls basswood the favorite tree of honeybees and beekeepers. For other trees and perennials that keep bees fed through the season, see plants for a continuous-bloom bee corridor.

Do linden trees kill bees? Dead bees are sometimes found under lindens, especially late-blooming silver lindens, and the flowers were long blamed for a sugar (mannose) that is toxic to bees. A 2017 review in Biology Letters found no experimental evidence for toxicity in linden nectar and concluded that the deaths probably result from starvation, because nectar runs short late in the trees' flowering period. The authors recommend making sure enough alternative food is available in late summer, which is a good reason to plant late-blooming nectar sources alongside lindens.

Pests and diseases

• Japanese beetles: University of Minnesota Extension lists linden among the adult beetles' preferred plants, and Michigan State University calls them littleleaf linden's principal pest. Adults skeletonize leaves in midsummer, but UMN notes the damage usually affects only appearance and healthy, mature trees can tolerate it. Management options are in the Japanese beetle guide.
• Linden aphid: a honeydew nuisance more than a tree health problem (see above).
• Other problems: Missouri Botanical Garden reports no serious insect or disease problems on American linden, though verticillium wilt is infrequent but can be fatal, powdery mildew, leaf spots and cankers may occur, and spider mites can do significant damage in hot, dry periods.

Basswood wood

Is basswood a hardwood? Yes. Like all broadleaf trees, basswood is classed as a hardwood, but it is one of the softest and lightest of them. Iowa State University Extension describes the wood as very light, soft, easily worked and almost white, and calls it one of the favorite woods for carvers; it is also used for boxes, crates, veneer and hidden furniture parts.

Common mistakes

Frequently asked

What is a linden tree?

A linden is any tree in the genus Tilia, called basswood in North America and lime in Britain. Lindens are large shade trees with heart-shaped leaves and fragrant, pale yellow early-summer flowers that hang from a strap-like bract. The common species are American basswood, littleleaf linden and silver linden.

What does a linden tree look like?

Lindens have a dense, rounded to pyramidal crown, heart-shaped leaves with a lopsided base and toothed edges, and gray bark that breaks into long ridges and furrows with age. In early summer they carry clusters of small, pale yellow flowers attached to a narrow leafy bract, followed by small, hard nutlets on the same bract.

Where do linden trees grow?

American basswood is native from Quebec and southeastern Canada through the eastern United States, west to the eastern Dakotas and Oklahoma, and prefers moist, fertile soils. Littleleaf linden is European, and silver linden is also non-native. In landscapes, lindens grow across roughly USDA zones 2 to 8, depending on the species.

Are linden trees messy?

Moderately. The main nuisance is sticky honeydew from linden aphids, which lands on cars and patios and can turn black with sooty mold, plus flower, bract and fruit drop and, on American linden, sprouts from the base. Siting the tree away from parking and seating avoids most of the trouble.

What is the difference between American linden and littleleaf linden?

American linden (Tilia americana) is native, with leaves about 3 to 6 inches long, a larger crown and poor tolerance of city conditions. Littleleaf linden (T. cordata) is European, with much smaller, shiny leaves, a denser, more formal crown and strong tolerance of urban conditions.

Is basswood a hardwood?

Yes. Basswood comes from a broadleaf tree, so it is botanically a hardwood, but it is among the softest and lightest hardwoods. Iowa State University Extension calls it one of the favorite woods for carvers because it is soft, light and easily worked.

Do linden trees kill bees?

Probably not through toxicity. A 2017 review in Biology Letters found no experimental evidence for toxicity in linden nectar and concluded that bee deaths under late-blooming silver lindens most likely result from starvation as nectar runs low. Planting other late-summer flowers nearby gives bees alternative food.

Sources

1. American Basswood, Iowa State University Extension and Outreach, Forestry
2. Tilia americana, Missouri Botanical Garden Plant Finder
3. Little-leaved linden, Tilia cordata, The Morton Arboretum
4. Silver linden, Tilia tomentosa, The Morton Arboretum
5. Little-leaf Linden (Smart Tree Selections), Michigan State University Extension
6. Greenspire Littleleaf Linden, Utah State University Extension
7. Silver Linden (Oklahoma Proven), Oklahoma State University Extension
8. Linden (Tilia): Linden aphid, Washington State University HortSense
9. Do linden trees kill bees? Reviewing the causes of bee deaths on silver linden (Tilia tomentosa), Biology Letters (abstract via PubMed)
10. Japanese beetles in yards and gardens, University of Minnesota Extension
11. Choosing "Sewer-Safer" Trees (SP628), University of Tennessee Extension (via UT Municipal Technical Advisory Service)

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