General: Basswood family (Tiliaceae). Native, large deciduous trees, the bark gray and furrowed with flat ridges. Leaves deciduous, alternate, more or less unevenly heart-shaped or the base often nearly truncate, petiolate, the blades 5-12.5 cm wide, thick and slightly leathery, with shallowly toothed margins, glabrous on both sides or with some pubescence on the lower surface. Flowers yellowish-white, 10-14 mm broad, fragrant and nectar-bearing, in drooping, 6-20-flowered clusters hanging on a stalk that diverges from near the center of an oblong, leaflike and strongly veined bract 5-10 cm long. Fruits mostly globose, 8-10 mm broad, hard and dry, indehiscent. The common name is from “bastwood,” referring to use of the inner bark, the “bast,” for rope, baskets, etc.
Variation within the species:
North American basswoods have been separated into many species (usually three or four) or treated as several varieties within only a single species. “Given the inconstancy of most vegetative and reproductive characters [of North American basswood], the ecophenic, ecotypic, and seasonal variation in vestiture, and also the probability of introgression,” trichome morphology provides the best evidence for recognizing the component taxa (see Hardin 1990).
a. Tilia americana var. americana
synonym: Tilia neglecta Spach
b. Tilia americana var. heterophylla (Vent.) Loud.
synonym: Tilia heterophylla Vent.
synonym: Tilia michauxii Nutt.
c. Tilia americana var. caroliniana (P. Mill.) Castigl.
synonym: Tilia caroliniana P. Mill.
synonym: Tilia floridana Small
The varieties of Tilia americana intergrade, but in their typical forms are separated as follows:
a. Leaves green beneath, sometimes glaucous, glabrous or sparsely hairy with simple trichomes, sometimes with a few stellate ones. var. americana
a. Leaves pale or whitish beneath from the close tomentum of dense, sessile-stellate trichomes, sometimes glabrate with age but remaining stellate-pubescent at least along the major veins. (b)
b. Young twigs tomentose or tomentose-hirsute; clusters of hairs on leaves more than 0.5 mm wide.
b. Young twigs glabrous; clusters of hairs on leaves less than 0.5 mm wide. var. heterophylla
Trees identified as Tilia neglecta may be variants of var. americana or they have been suggested to be introgressants between var. americana and var. heterophylla. Tilia floridana is often recognized as separate entity.
Distribution: Tilia americana is native to the Northern Deciduous and Great Lakes - St. Lawrence forest regions of North America. It also extends into grassland areas along river courses in Manitoba and the mid-western United States, where it forms a component of riverine gallery forests. In Canada, it is found from western New Brunswick into southern and central Québec and Ontario, extending as far west as north-western Ontario (along the U.S. border) and southern Manitoba. In the United States, the species occurs as far south as the mountainous regions of North Carolina, Tennessee, and northern Arkansas. The western limit for the species is south-central Manitoba and North Dakota, and along the Niobrara River in north-central Nebraska. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Linn, American linden, white basswood (var. heterophylla), American basswood
Range and Habitat in Illinois
Regularity: Regularly occurring
Regularity: Regularly occurring
Maine west to southern Quebec, southern and western Ontario, Michigan,
Minnesota, and southeastern Manitoba; south to eastern North
Dakota, northern and eastern Nebraska, eastern Kansas, and northeastern
Oklahoma; east to northern Arkansas, Tennessee, western North Carolina,
and New Jersey .
Occurrence in North America
MA MI MN MO NE NH NJ NY NC ND
OH OK PA RI SC SD TN VT VA WV
WI MB NB ON PQ
Basswood occurs on rich, mesic sites (coves, lower slopes, river bottoms), usually on deep, well-drained soils. It rarely occurs in pure stands but is usually mixed with other forest species. Var. americana is codominant in the sugar maple-basswood cover type and all varieties are a common component of many other rich forests. Basswood occurs up to 1500 meters elevation in the southern Appalachian Mountains. Flowering May-June (-July), usually 1-4 weeks after the leaves appear in mid-May. Seeds are dispersed in October.
Basswood is a native deciduous tree. Mature heights range from 75 to
130 feet (23-40 m) with diameter ranges from 36 to 48 inches (91-122 cm)
. The bark of mature trees is up to 1 inch (2.54 cm) thick at the
base of the trunk [2,15]. The bark is furrowed into narrow,
flat-topped, firm ridges with characteristic horizontal cracks; young
trees have smooth, thin bark . The inflorescence is a drooping
axillary cyme. The fruit is dry, hard, indehiscent, subglobose to
short-oblong, and is usually 0.2 to 0.28 inch (5-7 mm) in diameter, and
bears one or two seeds .
The root system of basswood is composed largely of lateral roots; it
does not usually form a taproot . Basswood root depths are usually
shallow relative to associated species root depths. In prairie soils
bur oak (Quercus macrocarpa), shellbark hickory (Carya lacinosa), and
northern red oak all have deeper roots than does basswood. Maximum root
depth in basswood averages 1.2 feet (36.5 cm) the first year, and 5 to 6
feet (1.5-1.8 m) by the third year; roots are not well developed below
approximately 2 feet (61 cm) . On prairie soils the deepest roots
of a 28-year-old basswood were 27 feet (8.2 m) but most of the roots
were in the top 4 to 5 feet (1.2-1.5 m) of soil . Adventitious
roots will develop as the stem is buried, as occurs on the sand dunes
near southern Lake Michigan .
The tree crown is usually broad and rounded, but in close stands is more
columnar. The branches are small, weak, and often pendulous .
Maximum longevity is approximately 200 years .
Range and Habitat in Illinois
mixed deciduous forests. It is sometimes found in swamps .
Basswood is generally confined to sandy loams, loams, or silt loams, and
achieves its best growth on the finer textured soils. Best growth is on
mesic sites, but basswood will also grow on coarse soils that are well
drained. In Wisconsin basswood exhibits a bimodal distribution with
respect to moisture; it achieves peak importance values on wet-mesic
sites and on dry-mesic sites, but is "outcompeted" by sugar maple on mesic
sites . In southern Wisconsin, maple-basswood forests are largely
restricted to northern exposures . Basswood is moderately tolerant
of flooding; it occurs on floodplain sites that have probabilities of
annual flooding between 50 and 100 percent . Acceptable soil pH
ranges from 4.5 to 7.5, though basswood occurs most often on less acidic
to slightly basic soils. Because basswood is nitrogen demanding it
grows poorly on nitrogen deficient soils .
At the western limits of its range, basswood usually grows on the
eastern side of lakes and along major drainages where it is naturally
protected from fire. Basswood is commonly found in ravines and
protected, moist sites at the prairie-woodlands interface in Nebraska
. In North Dakota and Minnesota basswood achieves its highest
densities on intermediate slopes; it is found in lower numbers on both
the drier uplands and the wet bottomlands . According to Crow ,
basswood's distribution is more closely associated with edaphic and
moisture conditions than with fire.
The maximum elevation at which basswood is found is 4,930 feet (1500 m)
in the southern Appalachian Mountains .
Key Plant Community Associations
Basswood generally occurs in mixed stands and rarely forms pure stands
. It is codominant in the sugar maple (Acer saccharum)-basswood
cover type, and is a common component of many other mesophytic forests .
Associates in the sugar maple-basswood type include white ash (Fraxinus
americana), northern red oak (Quercus rubra), eastern hophornbeam
(Ostrya americana), red maple (A. rubrum), and American elm (Ulmus
americana) [16,24]. Typical sugar maple-basswood communities in
Wisconsin and Minnesota include 21 percent northern red oak, 35 percent
basswood, 17 percent sugar maple, and 17 percent other species . To
the east, eastern hemlock (Tsuga canadensis) may be present, and
communities on mesic sites would be more like the following: 52 percent
sugar maple, 27 percent basswood, 14 percent yellow birch (Betula
alleghaniensis), 4 percent eastern hemlock, and 3 percent other species .
Publications in which basswood is listed as a dominant, codominant,
or indicator species include:
The vegetation of Wisconsin 
The principal plant associations of the Saint Lawrence Valley 
Deciduous forest 
A forest classification for the Maritime Provinces 
A classification of the deciduous forest of eastern North America .
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K081 Oak savanna
K095 Great Lakes pine forest
K099 Maple - basswood forest
K100 Oak - hickory forest
K101 Elm - ash forest
K102 Beech - maple forest
K103 Mixed mesophytic forest
K104 Appalachian oak forest
K106 Northern hardwoods
K107 Northern hardwoods - fir forest
K108 Northern hardwoods - spruce forest
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES10 White - red - jack pine
FRES15 Oak - hickory
FRES17 Elm - ash - cottonwood
FRES18 Maple - beech - birch
FRES19 Aspen - birch
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
1 Jack pine
20 White pine - northern red oak - red maple
21 Eastern white pine
23 Eastern hemlock
24 Hemlock - yellow birch
25 Sugar maple - beech - yellow birch
26 Sugar maple - basswood
27 Sugar maple
28 Black cherry - maple
39 Black ash - American elm - red maple
42 Bur oak
52 White oak - black oak - northern red oak
55 Northern red oak
58 Yellow-poplar - eastern hemlock
59 Yellow-poplar - white oak - northern red oak
Soils and Topography
Basswood grows best on mesic sites, but it is also found on coarse soils such as the sand dunes near Lake Michigan (17) and on dry, exposed rock ridges in Ontario and Quebec (25).
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 (9,17).
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 (19). Basswood is restricted to more mesic sites in southern Illinois and in northern Kentucky (5). 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 (13,28).
Seed production begins in basswoods about 15 years old (or as early as 8 years) and continues until the trees reach at least 100 years. Heavy seed crops are irregular but good quantities of seed are produced at 1- to 3-year intervals. Germination in the first year or two is often poor, apparently because of an impermeable testa, but seeds may remain dormant and viable in seed banks for up to three years. Few established seedlings are found where the species forms a major component of the canopy, apparently because seedling loss from herbivory by rabbits and deer.
Seedlings can establish in as little as 25% of full sunlight, but heavy shade limits subsequent growth and development. Seedling growth begins slowly, but established young trees are fairly fast-growing. The typical life of a basswood is about 100 years but some are known to live 140-200 years.
Basswood stump sprouts are often very common, and this may produce trees growing in close clusters. Stump sprouts arise from the main stem after its death, fire or logging injury, or aging, or even after disturbance of the surrounding stand. Almost all basswoods 10 cm or less d.b.h. will sprout from the stump, and sprouts have been obtained from basswoods over 100 years old.
Flower-Visiting Insects of American Linden in Illinois
(Halictid bees suck nectar or collect pollen, other insects suck nectar; all observations are from Robertson)
Apidae (Apinae): Apis mellifera sn fq; Apidae (Bombini): Bombus pensylvanica sn
Halictidae (Halictinae): Augochlorella striata sn, Augochloropsis metallica metallica sn fq, Halictus rubicunda sn, Lasioglossum coriaceus sn, Lasioglossum forbesii sn, Lasioglossum illinoensis sn, Lasioglossum imitatus sn cp fq, Lasioglossum pectoralis sn, Lasioglossum versatus sn, Lasioglossum zephyrus sn cp fq
Sphecidae (Sphecinae): Sphex ichneumonea; Tiphiidae: Myzinum quinquecincta; Vespidae (Eumeninae): Euodynerus foraminatus
Syrphidae: Allograpta obliqua, Eupeodes americanus, Orthonevra nitida; Tachinidae: Archytas aterrima, Tachinomyia panaetius; Calliphoridae: Calliphora vicina, Lucilia illustris, Phormia regina; Muscidae: Graphomya americana, Neomyia cornicina fq; Fanniidae: Fannia manicata
Ctenuchidae: Cisseps fulvicollis
Melyridae: Malachius erichsonii
Associated Forest Cover
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 (Ulmus americana).
Although not a dominant species, basswood is also found in the following forest cover types:
21 Eastern White Pine
23 Eastern Hemlock
20 White Pine-Northern Red Oak-Red Maple
24 Hemlock-Yellow Birch
27 Sugar Maple
25 Sugar Maple-Beech-Yellow Birch
28 Black Cherry-Maple
60 Beech-Sugar Maple
39 Black Ash-American Elm-Red Maple
42 Bur Oak
58 Yellow-Poplar-Eastern Hemlock
62 Silver Maple-American Elm
Basswood is one of the major species, with sugar maple, beech (Fagus), ash (Fraxinus), hickory (Carya), and oak (Quercus), in the Deciduous Forest Region of southern Ontario. It is a minor component of the sugar maple-yellow birch-hemlock-white pine climax forest type in the southern districts of the Great Lakes-St. Lawrence regions of Ontario (32).
In the Mixed Mesophytic forests of the southern Appalachians, Tilia americana is replaced by T. heterophylla (9). The genotypic distinction between these species is not always clear, and T. americana does appear in the northern part of the Mixed Mesophytic region.
Diseases and Parasites
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 overmature 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) (1,22). In New England, American basswood is a highly preferred host for gypsy moth (21), while in southern
Quebec, it was classified as intermediate in susceptibility to gypsy moth defoliation (27).
The foliage is host to various diseases-anthracnose (Gnomonia tiliae), black mold (Fumago vagans), and leaf spot (Cercospora microsora)-but none seem to do serious damage. The wood of basswood decays easily and once exposed can be host to many of the common hardwood decay organisms such as the yellow cap fungi (Pholiota limonella) and Collybia velutipes. Phellinus igniarius, Ustulina deusta, and nectria canker (Nectria galligena) also are found on basswood.
Little defect is encountered in basswood when harvested before it reaches 120 years of age. Beyond this age, the chances of losses due to decay are greatly increased. Cull studies in the forests of Ontario indicate that yellow-brown stringy rot was the most common bole defect encountered; brown stain, some incipient yellow rot, and green stain were also found (8).
The thin bark of this species is easily damaged by fire (13). Basswood is one of the hardwoods least susceptible to late spring frosts (40).
Fire Management Considerations
The high heat value of basswood wood is reported as 8,342 Btu per pound,
the low heat value averages 7,817 Btu per pound. The rate of fire
spread under laboratory conditions for basswood wood is higher than that
in white fir (Abies concolor), sugar maple, southern magnolia (Magnolia
grandiflora), and longleaf pine (Pinus palustris). Basswood contains an
oil that is rich in volatile fatty acids .
Small basswood slash, up to 2 inches (5 cm) in diameter, is usually very
quick to rot; that of most northern hardwood species, including
basswood, is almost completely decayed in 4 to 7 years. Under average
conditions, basswood logs and stumps are not a serious source of fire
danger after 10 to 12 years, and after 15 to 18 years, nothing remains
except mounds of moldy wood . Basswood logs and slash are easily
water saturated, however, which slows the rate of decay .
Fuel values for herbicide-killed basswood (as firewood) have been
Prescribed fire is not recommended for established stands of hardwoods
in which basswood occurs; basal fire wounds increase susceptibility to
butt rot . Use of fire in cut stands may improve resistance to butt
rot in the next generation of basswood, since fire lowers the level at
which stump sprouts form .
Broad-scale Impacts of Plant Response to Fire
The Research Project Summary Effects of surface fires in a mixed red and
eastern white pine stand in Michigan and the Research paper by Bowles
and others 2007 provide information on prescribed fire and postfire response
of several plant species, including basswood, that was not available when
this species review was written.
Plant Response to Fire
A prescribed fire in an aspen stand in which basswood occurred
top-killed most of the trees in the stand. Those stems not killed by
the fire were felled to eliminate overstory competition. All of the
top-killed basswood stems sprouted (stems ranged in size from 4 to 17
inches [10-43 cm] in diameter), producing an average of 21 sprouts per
clump within 5 years of the fire .
Fire wounding of basswood increases susceptibility to butt rot : of
trees with basal fire wounds, 100 percent of basswood stems had butt
rot, resulting in a cull rate of 39 percent .
Light surface fires favor sugar maple seedlings over basswood (and other
hardwoods). Hotter fires destroy existing reproduction of sugar maple
and create openings favoring basswood. Basswood sprouts are less
abundant in stands escaping fire for extremely long periods of time,
presumably because the heavy shade created by very dense stands is not
tolerated by basswood reproduction .
Immediate Effect of Fire
had previously been classified as oak savanna. The low intensity fire
burned into adjacent closed canopy sugar maple-basswood forest. Fuel
loading in the closed forest was approximately 530 g/sq m. Mortality of
basswood stems under 4 inches in diameter (10 cm) was close to 10
percent (some of these were apparently only top-killed). Larger stems
were apparently unaffected by the fire .
Basswood is rated as a fire sensitive species; the thin bark is easily
damaged by fire, as are the shallow roots . However, basswood that
has been top-killed by fire will sprout vigorously from the root crown .
Basswood is most common in forests with long fire-free intervals. Fire
suppression has apparently encouraged its increase. In the absence of
fire, paper birch (Betula papyrifera)-eastern white pine-bur oak forests
are being replaced in by basswood, balsam fir (Abies balsamea), and
black ash (Fraxinus nigra) in the north-central states . Basswood
and sugar maple usually replace postfire aspen stands (Populus
tremuloides and P. grandidentata) on rich, moist sites in Minnesota
. The presence of sugar maple-basswood stands is correlated with
longer fire-free intervals in Minnesota; pines (including white pine,
red pine [Pinus resinosa] and jack pine [P. banksiana]) and aspens
occur on sites that burn more frequently . In jack pine or red
pine-white pine stands which experience frequent fire, basswood is rare
. Basswood occurs in moist canyons in Nebraska that appear to be
refuges from fire . Also in Nebraska, basswood and other hardwoods
are more common than they were 130 years ago, and it is thought that
this is related to a decrease in the frequency and severity of fires
. In New England northern hardwood forests that include basswood
typically have fire-free periods on the order of 800 to more than 2,000
Many authors report that hardwood forests including basswood are
encroaching onto former grasslands since fires have been suppressed
[1,3,38,60,72]. In Iowa oak savanna is replaced by dense sugar
maple-basswood forest process in approximately 200 years without fire
. In Wisconsin basswood are invading mixed oak stands from which
they had formerly been excluded by wildfire . However, Auclair and
Cottam  stated that this is not a general trend; succession to sugar
maple-basswood is confined to specific sites largely because of
fragmentation of forests and the resultant lack of seed sources. They
do concur that red oak stands may represent sugar maple-basswood sites
that have either been retrogressed to oak by fire, or from which sugar
maple and basswood have been excluded by fire .
A stand of basswood and eastern hophornbeam in Minnesota contained
scattered open-grown, large bur oaks. The basswood and eastern
hophornbeam were even-aged. Sugar maple was not present in the dominant
layer even though its presence would normally be expected. The forest
structure was explained by Daubenmire  as a sugar maple-basswood
stand that had experienced a brief period of burning. Daubenmire
proposed the following relationship of sugar maple-basswood forests to
fire: 1) sugar maple is eliminated by single fires; 2) repeated fires
eliminate elms and red oak and leave basswood and eastern hophornbeam as
sprout thickets; 3) continued fires can eliminate basswood and eastern
hophornbeam thickets, which are replaced by bur oak and grasses; 4)
severe fires will eventually eliminate bur oak, leaving prairie. The
structure of the forest described above was explained as the result of
sugar maple-basswood-eastern hophornbeam invasion of a bur oak savanna
(possibly stage 3). The sugar maple forest developed to maturity
without experiencing fire. This forest then experienced a short period
of burning (perhaps only one fire) and had reached stage 2 when burning
ceased, leaving the basswood and eastern hophornbeam to grow up into an
even-aged canopy. Daubenmire concluded that the climatic limits of
sugar maple-basswood are further west than the actual limits due to fire
. In Iowa oak savanna is replaced by dense sugar maple-basswood
forest, the process occurring over the course of approximately 200 years
without fire .
Mature sugar maple-basswood forests are very resistant to burning.
Decomposition of potential fuels is rapid, particularly on base-rich
mull soils. Dense shade reduces the numbers and cover of shrubs and
herbaceous species, and therefore very little fuel exists at ground
level. The tree trunks are not very flammable, and the open crowns do
not carry fire well. Low solar radiation, high relative humidity, and
low wind speeds enhance the moisture retention of ground-level fuels,
thereby inhibiting ignition and/or spread of fire. Ordinarily, only the
leaf litter ever reaches a flammable state, creating conditions
conducive only to patchy, creeping surface fires .
The Minnesota Big Woods (sugar maple-basswood cover type) is often
described as an old, stable, climax forest. New evidence suggests that
in fact, these woods are of comparatively recent origin . Climate
factors (increased moisture and lower temperatures) contributed to a
natural decrease in the frequency and intensity of fire. Once
established, sugar maple-basswood forests do not burn easily ,
creating conditions in which these forests were able to survive climatic
warming and increases in fire frequency. The extent of these woods has
been greatly reduced by human activities, but they have also experienced
lower danger from fire since humans have stopped setting fires and have
been active in suppressing fires .
Basswood occurs in aspen forests which are of postfire origin and
fire-maintained. The fire regime in these woods usually consists of
short fire intervals (on the order of 10 years) with low intensity
surface fires. Where these forests are protected from fire, closed
canopies and higher species diversity develop .
More info for the terms: climax, fire exclusion, importance value, presence, succession
Facultative Seral Species
Basswood is moderately tolerant of shade. It achieves its highest
densities in sugar maple-basswood stands that are late successional to
climax forests. Sugar maple-basswood can eventually replace oak-hickory
on favorable upland sites in the upper Midwest. Succession of
oak-hickory to sugar maple-basswood can be accelerated where harvesting
or other disturbance releases the tolerant understory species .
Braun  classified basswood as a member of the regional climax forest
in Ohio that also contains American beech (Fagus grandifolia), ash
(Fraxinus spp.), sugar maple, and yellow-poplar (Liriodendron
tulipifera). In eastern Nebraska northern red oak and basswood are
described as climax dominants at the western limits of the forest .
In New York basswood is a subclimax species, where it may increase in
importance after heavy logging . In Minnesota sugar maple-basswood
communities are climax on fine mineral soils. In Itasca State Park,
Minnesota, succession from prairie to white pine (Pinus strobus)-bur oak
to sugar maple-basswood is explained by fire exclusion and/or increased
moisture. The authors concluded available evidence supports the climate
model better than the fire exclusion model .
The persistence of the moderately shade tolerant basswood in stands
containing highly shade tolerant sugar maple is dependent on their
differing modes of reproduction. Sugar maple produces large numbers of
seedlings which are positively correlated with the occurrence of
basswood in the canopy . Stump sprouting allows basswood to
maintain itself in a stand with the more shade-tolerant sugar maple;
basswood stump sprouts can reach canopy size faster than the more
numerous maple seedlings [16,27,71].
Patchy or large scale disturbance may favor basswood because of its
sprouting ability and presence in the understory. Basswood increased in
relative importance value after a tornado caused severe damage to a
sugar maple-Ohio buckeye (Aesculus glabra) stand in Indiana. The source
of the increase was not specified by the authors; it may have come from
stump sprouts and/or released individuals, coupled with the loss of
other species .
The youngest recorded age at which basswood first reproduces is 15 years
. Basswood flowers are insect pollinated, mostly by bees and flies
. Basswood produces good quantities of seed at 1- to 3-year
intervals [16,30]. The relatively heavy fruits are not usually carried
long distances by the wind [42,52]. Seeds can remain dormant for up to
3 years . This deep dormancy is thought to be caused by an
impermeable seedcoat, dormant embryo, and tough pericarp. Acid
scarification and cold stratification enhance seed germination on
mineral soil [16,42,58], but few seeds actually germinate under normal
Shade enhances establishment and initial survival, but heavy shade
limits subsequent growth and development . Seedlings can establish
in as little as 25 percent of full sunlight . The higher soil
temperatures in forest openings are better suited for good seedling
growth , but seedlings are sensitive to soil nutrient deficiencies
which may render them less tolerant to shade than older trees .
However, dense reproduction is only obtained under partial canopies .
Most basswood reproduction originates as stump sprouts. Almost all
basswood trees 4 inches (10 cm) or less d.b.h. will sprout from the
stump, and more than 50 percent of sawlog-size trees will sprout as well
. Sprouts have been obtained from basswood trees over 100 years
old; 57 percent of trees 20 inches [50.8 cm] or more in diameter
Growth Form (according to Raunkiær Life-form classification)
Reaction to Competition
For reproduction from seed, the shelterwood system should provide the partial shade necessary to control competing vegetation, and to create a microclimate suitable for germination. After basswood is established, the overstory should be removed.
Closely spaced, forest-grown trees develop straight, columnar trunks and narrow crowns, but open-grown trees have short stems and many large branches.
Life History and Behavior
Basswood usually flowers in June, but flowering dates range from late
May to early July . Flowering occurs from 1 to 4 weeks after spring
leaf-out [1,16]. In Minnesota, bud swell occurs in from late April to
early May, and leafing out occurs from early to mid-May. Seeds are
dispersed in October, and leaf fall occurs from September to October .
Because an extensive root system already exists, a basswood sprout has a higher probability of replacing a parent stem than does a sugar maple seedling. Thus, the ability to produce abundant stump sprouts allows basswood to maintain itself in a stand with the more shade-tolerant maple despite the much larger numbers of sugar maple in the subcanopy (13).
Shading aids the establishment and initial survival of basswood seedlings but heavy shade limits subsequent growth and development, and vigorous growth is unlikely under the forest canopy. Likewise, higher soil temperatures found in forest openings are suitable for greatest growth of basswood seedlings (3).
Basswood seedlings first develop a long taproot, which is soon supplemented by lateral roots. First-year seedlings had a root penetration of 20.3 cm (8 in) with a lateral spread of 7.6 cm (3 in), and second-year seedlings had a root penetration of 21.3 cm (8.4 in) and a lateral spread of 18.3 cm (7.2 in) (30). Stem height was 5.6 cm (2.2 in) the first year and 9.4 cm (3.7 in) the second year.
Cold storage of autumn-lifted basswood seedlings maintains root growth capacity and overall seedling vigor for spring planting. Autumn-lifted stock should be stored at a temperature of 5° C (41° F) and a relative humidity of 70-85 percent (46).
Basswood has been successfully planted in Ontario on cutover land and abandoned farmland. On cutover land, survival was best when a light overhead canopy (8.0 m/ha or 35 ft/acre of residual basal area) controlled competing vegetation (36). Release of the seedlings from the residual overstory and undergrowth was recommended after three growing seasons. Fall plantings failed to survive. Early failures of hardwoods planted on old-field sites in Ontario have been attributed to the absence of mycorrhizal fungi (30), insufficient site preparation, and insufficient postplanting weed control (42,44). Fertilization at the time of planting had little effect on seedling survival or growth (43).
Seed Production and Dissemination
The seed-bearing age for basswood generally ranges from 15 to 100 years, but seed production at age 8 years (10 years from seed) has been noted (45). The number of ripened fruits averages 9,700 to 13,200/kg (4,400 to 6,000/lb); green fruit averages 5,070 to 5,950 seeds per kilogram (2,300 to 2,700/lb) of fruit (17,33,35). Based on a number of collections, seed weights varied from 12 to 38 mg (0.18 to 0.59 gr) and averaged 31 mg (0.48 gr) (4). In a study for 26 years of 19 species in northern Wisconsin, basswood was one of the most consistent fall-maturing seed producers (18). It produced good seed crops 62 percent of the time from 1949 to 1974. When crown-released, basswood that were about 50 years old did not increase their fruit production during the 5-year period following release. Moreover, the quality of fruit remained poor throughout this period. In the third year after release, for example, only 5 percent of the fruit collected from the ground contained sound seed (37).
The production of fruit without seed (parthenocarpy) and seed infestation by a lepidopterous larva are two common defects that affect seed viability. A pin hole in the pericarp indicates the presence of the larvae. The percentage of fruits with the pin hole was 3 percent in a September collection and 7 percent for an October collection in southeastern Ontario (35); 30 percent of fruits were insect infested in 45 collections from various parts of the natural range of basswood (4). In the same collections, the percentage of fruits with seed ranged from 0 to nearly 100, but the lack of sound seed on the forest floor seems to be the rule. Only 2 percent were sound out of more than 7,400 identifiable basswood seeds found in the litter in a northern Wisconsin stand. Seeds covered by leaves had rotted and most of the seeds lying on or in the upper litter layers had been destroyed by rodents (18).
Flowering and Fruiting
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 (34). Individual trees tend to consistently produce fruit of a particular form and size.
Growth and Yield
Basswood grows faster than most other northern hardwood species. On the same site, basswood often exceeds sugar maple and yellow birch (Betula alleghaniensis) in site index by 1.5 rn (5 ft) and beech by 3 rn (10 ft) (11).
Diameter growth for basswood averaged 3 mm. (0.11 in) per year in three unmanaged stands in northeastern Wisconsin (site index at base age 50 years for basswood of 21.3 m or 70 ft). The same site under managed conditions produced substantially higher growth rates. Annual diameter growth average for a crop tree release was 4.6 mm (0.18 in); for a 20.7 m² and 17.2 m² /ha (90 ft² and 75 ft² /acre) (residual sawtimber) selection cut, it was 3.8 and 4.8 mm (0.15, 0.19 in); and for a group selection cut, it was 3 mm (0.12 in). Relatively narrow bark ridges and V-shaped fissures, with new light-colored inner bark visible in the fissures, represent a high-vigor basswood. In contrast, low-vigor trees have scaly bark with wide bark ridges and shallow, short fissures, frequently producing a rather smooth surface (12).
Two phases can be noted in the renewal of cambial activity for basswood. The first phase is the reactivity of cambium that occurs independently of the initial meristematic activity within the overwintering buds. The second phase, accelerating cambial activity after bud-break, is presumably under the influence of primary growth (14). Winter stem contraction for basswood often exceeds stem expansion from the previous growing season. The amount of winter shrinkage in basswood stems was greater than that of yellow birch, sugar maple, or hemlock (Tsuga canadensis) (49).
The period of shoot elongation for basswood in northern areas is shorter than that for other hardwoods-only red oak and sugar maple had shorter periods of terminal shoot elongation among seven species studied in northern Wisconsin. Based on an average of three growing seasons, shoot elongation for basswood began in May and was completed by the first of June (10). Longer periods of shoot elongation have been noted for open-grown basswood in Illinois and basswood plantations in Ontario (mid-May to mid-August). Chlorophyll is found in xylem rays and primary xylem of basswood twigs (47). Although the photosynthetic contribution is not large, it may have seasonal significance when leaves are absent.
Molecular Biology and Genetics
Barcode data: Tilia americana
Statistics of barcoding coverage: Tilia americana
Public Records: 5
Specimens with Barcodes: 7
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status and wetland indicator values.
Basswood stump sprouts can be managed for sawtimber . The number of
stump sprouts declines with the age and size of the cut trees .
Since sprouts originating at or below the ground line are more resistant
to butt rot, stumps should be cut very close to the ground  or
burned . Early thinning of sprouts is needed to ensure good quality
and rapid growth . In West Virginia an average of 14.4 7-year-old
stump sprouts per clump was removed to allow good growth of the
remaining one or two stems . Larger stems (greater than 51.7 inches
[1.31 m] d.b.h. will also respond to release .
Direct seeding may also have potential for good basswood regeneration
; natural seed reproduction can be encouraged by shelterwood cutting
systems . Shelterwood systems also enhance basswood production
where advance regeneration is large enough to compete successfully with
other hardwoods and shrubs . Advance growth should be 2 feet (0.6 m)
or more in height before the overstory is harvested . Sites that
are harvested to 60 percent residual stems may need to be cut again to
allow the best growth of northern hardwoods (including basswood) .
Even-aged management systems can also be used successfully for basswood,
particularly where sprouts have been properly thinned .
Basswood and other tolerant species are often established in the
understory of oak (Quercus spp.)-hickory (Carya spp.) stands, and tend
to take over a site when the overstory is harvested, regardless of the
silvicultural system used . Basswood invasion of mixed oak stands
is a problem for oak regeneration in Wisconsin .
High densities of white-tailed deer can result in basswood seedling
height growth reduction or even complete loss of basswood from the stand
due to overbrowsing . On old-field sites basswood is often subject
to damage from mice and voles girdling the stems. Rabbits also feed
heavily on seedlings and small saplings. Seed predators include mice,
squirrels, and chipmunks .
Insect pests of basswood include the linden borer (which damages weak,
very young, or "overmature" trees) and the following defoliators: linden
looper, basswood leafminer, spring cankerworm, fall cankerworm,
white-masked tussock moth, gypsy moth, and forest tent caterpillar.
None of these pests is considered a serious threat . Basswood is
easily decayed by fungi, and butt rot is an important factor in loss of
merchantable timber .
Basswood is susceptible to many herbicides, but is resistant to 2,4-D
and 2,4,5-T .
Cultivars, improved and selected materials (and area of origin)
These plant materials are readily available from commercial sources. Cultivars of Tilia americana have been selected for mature shape, fall leaf color, and rust resistance. Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Basswood stump sprouts can be managed for saw timber. The number of sprouts declines with the age and size of the cut trees. Since sprouts originating at or below the ground line are more resistant to butt rot, stumps should be cut very close to the ground or burned. Early thinning of sprouts is needed to ensure good quality and rapid growth.
Over-browsing by high densities of white-tailed deer can result in basswood seedling height growth reduction or even complete loss of basswood from the stand. Mice and voles on oldfield sites may often girdle the stems, and rabbits also feed heavily on seedlings and small saplings. Seed predators include mice, squirrels, and chipmunks. Basswood is easily decayed by fungi, and butt rot is an important factor in loss of merchantable timber.
Basswood is most common in forests with long fire-free intervals, because the thin bark and shallow roots are easily damaged by fire and basal fire wounds increase susceptibility to butt rot. Prescribed fire is not recommended for established stands of hardwoods in which basswood occurs, as too-frequent fire intervals eliminate basswood or restrict it to the most mesic sites. In some places, however, these trees are encroaching onto former grasslands since fires have been suppressed.
Relevance to Humans and Ecosystems
Other uses and values
Basswood is planted as a shade tree or ornamental . The fibrous
inner bark ("bast") has been used as a source of fiber for rope, mats,
fish nets, and woven baskets [15,16].
Value for rehabilitation of disturbed sites
Basswood is of limited use in mixed hardwood plantings on disturbed
sites in Ohio .
Importance to Livestock and Wildlife
flowers are visited by honeybees for nectar . The easily decayed
wood produces a disproportionate number of cavities which are used by
cavity-nesting animals including wood ducks , pileated woodpeckers
, other birds, and small mammals . Carey and Gill  rate
basswood as fair (their lowest rating) for all wildlife.
Wood Products Value
many other uses including cooperage, boxes, veneer, excelsior, and pulp
[15,16]. Basswood is economically important for timber, especially in
the Great Lakes States .
Carey and Gill  rated basswood as fair (their lowest rating) for
Ethnobotanic: Native Americans and settlers used the fibrous inner bark ("bast") as a source of fiber for rope, mats, fish nets, and baskets. Basswood is still valued for its soft, light, easily worked wood, especially for turned items and hand carving. It once was the material of choice for prosthetic limbs, but these are now made from synthetics. Other uses have included boxes, toys, woodenware, drawing boards, veneer, venetian blinds, excelsior, and pulp.
Native Americans used fresh basswood sap, which contains moderate amounts of sugar, as a watery drink or boiled it into syrup. They also ate young basswood leaves and used the cambium for soups and breads. Various medicinal uses were made of leaf and bark extracts, and Iroquois used freshly cut bark as an emergency bandage for wounds.
Wildlife: Basswood is good browse and buds are important for birds and deer in winter. Fruits are eaten by birds and small mammals. The wood decays easily and produces many cavities (especially in trees past 120 years of age), which are used by cavity-nesting animals (wood ducks, pileated woodpeckers, other birds, and small mammals). Basswood is a prolific nectar producer and pollination by honeybees results in a choice grade of honey.
Restoration: Basswood is planted as a shade tree or ornamental. For sites of smaller size or with compacted soils, other Tilia species may be more suitable. Basswood is said to be a soil-enriching species, bringing calcium and magnesium up from deep in the soil profile and depositing it in leaf litter on the surface.
Tilia americana is a species of Tilia native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Texas, and southeast to South Carolina, and west along the Niobrara River to Cherry County, Nebraska. Common names include American linden and basswood (also applied to other species of Tilia in the timber trade).
Tilia americana is a medium-sized to large deciduous tree reaching a height of 18 to 37 m (60 to 120 ft) exceptionally 39 m (129 ft) with a trunk diameter of 1-1.5 m (3–4 ft) at maturity. 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 (can grow up to 25 cm) long and broad, with a long, slender petiole, a coarsely serrated margin and an acuminate apex. 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 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. Flowering is in early to mid summer; pollination is by bees. The fruit is a small, globose, downy, hard and dry cream-colored nutlet with a diameter of 8–10 mm.
The circumscription of the species is disputed; some authors treat it in a narrow sense, with Tilia caroliniana, Tilia heterophylla, and Tilia mexicana regarded as separate species, while others treat these as varieties or synonyms of T. americana. The distribution and description above treat the species in its narrow sense; taken in the broad sense, including plants with the leaves white below with dense tomentum (velvety hairs), the distribution extends southwards to Florida, and in Mexico west to Sinaloa and south to Oaxaca.
This species is dominant in the Acer saccharum - Tilia americana association, most common in western Wisconsin and central Minnesota, but occurs as far east as New England and southern Quebec where the soils are mesic with relatively high pH. It also has minor occurrence in many other forest cover types.
Its flowers provide abundant nectar for insects. The seeds are eaten by chipmunks, mice, and squirrels. Rabbits and voles eat the bark, sometimes girdling young trees. The leaves serve as food for caterpillars of various Lepidoptera (see Lepidoptera which feed on Tilia). The ribbed cocoon maker species Bucculatrix improvisa has not been found on other plants.
Cultivation and uses
Tilia americana can be propagated by cuttings and grafting as well as by seed. The plants grow rapidly in a rich soil, but are subject to the attacks of many insect enemies.
Tilia Americana is known for being one of the most difficult native North American trees to propagate from seed, as they not only have a low viability rate (approximately 30% of all seeds are viable), but quickly develop an extremely hard seed coating that may delay germination for up to two years. If planting them, it is recommended to gather the seeds in early autumn and sow them before they dry out and form a coating. This will then allow germination to occur immediately. Overall, seeds are not a major part of the tree's reproductive strategy and it instead mostly spreads by suckering. All juvenile basswoods sucker extremely readily, and even old trees will often sprout from the stump if cut.
The species 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. It is often planted on the windward side of an orchard as a protection to young and delicate trees. It is cultivated at least as far north as Juneau, Alaska.
The foliage and flowers are both edible, though many prefer only to eat the tender young leaves. It is a beneficial species for attracting pollinators as well. Bees produce excellent honey with a mildly spicy flavor from its blossoms.
Cultivars include 'Nova', 'Duros' (with an upright crown), the pyramidal 'Frontyard' and the conic-crowned 'Redmond'.
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, but is sometimes confounded with tulip-wood and then called white-wood, and is largely used in the manufacture of wooden-ware, wagon boxes and furniture. It has a density of 0.4525. The wood is considered odorless. This makes it valuable in the manufacture of wooden-ware, cheap furniture, bodies of carriages; it is also especially adapted for wood-carving. The inner bark is very tough and fibrous, used in the past for making ropes.
It is a common wood for use in the production of solid body electric guitars, where it is considered an analogue for aspen and poplar, because it is light, strong and resonant, though it is usually used for guitars that will be painted an opaque color, because its lack of notable grain makes it an unattractive candidate for transparent finish. Linden wood rots easily and old trees have many cavities that serve as nesting places for birds.
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). That 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.
- U.S. Forest Service Silvis Manual: Tilia americana
- Germplasm Resources Information Network: Tilia americana
- USDA NRCS Tree Guide: Tilia americana (pdf file)
- Keeler, H. L. (1900). Our Native Trees and How to Identify Them. New York: Charles Scriber's Sons. pp. 24–31.
- Jones, G. N. (1968). Taxonomy of the American species of linden (Tilia). Illinois Biological Monographs 39. University of Illinois Press, Urbana.
- Hardin, J. W. (1990). Variation patterns and recognition of varieties of Tilia americana s.l. Syst. Bot. 15: 33-48. Abstract.
- Bioimages: Tillia americana ssp. heterophylla
- USDA: Managing the Japanese Beetle:A Homeowner’s Handbook
- Juneau: Downtown Juneau Tree Guide
- Porter, Terry (2006). Wood Identification & Use - Revised & Expanded. p. 254.
- Bradley P, ed. British Herbal Compendium. Vol. I. Dorset (Great Britain): British Herbal Medicine Association; 1992: 142-144
- Aguirre-Hernandez, E., Martinez, A. L., Gonzalez-Trujano, M. E., Moreno, J., Vibrans, H., & Soto-Hernandez, M. (2007). Pharmacological evaluation of the anxiolytic and sedative effects of Tilia americana L. var. mexicana in mice. J. Ethnopharmacol. 109 (1): 140-145.
Names and Taxonomy
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