Betulaceae -- Birch family

    Neil I. Lamson

    Sweet birch (Betula lenta), also commonly referred to as  black birch or cherry birch, was at one time the only source of  oil of wintergreen. It is the aroma of wintergreen emanating from  crushed leaves and broken twigs to which this birch owes its  common name, sweet. Its specific name, lenta, is   derived from the tough yet flexible twigs that characterize the  species. The wood is also unique. When exposed to air it darkens  to a color resembling mahogany and, in times past, was used as an  inexpensive substitute for the more valued tropical wood.

Sweet birch is primarily a tree of the northeastern United States.  It grows from southern Maine westward in southern Quebec, New  Hampshire, Vermont, New York, and southeastern Ontario to eastern  Ohio; and south in Pennsylvania through the Appalachian Mountains  to northern Alabama and Georgia. Forest survey data indicate that  sweet birch is most abundant in Massachusetts, Connecticut, New  York, and Pennsylvania.

   
  -The native range of sweet birch.

Betula lenta L.:
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Ont.; Ala., Conn., Ga., Ky., Maine, Md., Mass., Miss., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Trees , to 20 m; trunks tall, straight, crowns narrow. Bark of mature trunks and branches light grayish brown to dark brown or nearly black, smooth, close, furrowed and broken into shallow scales with age. Twigs with taste and odor of wintergreen when crushed, glabrous to sparsely pubescent, usually covered with small resinous glands. Leaf blade ovate to oblong-ovate with 12--18 pairs of lateral veins, 5--10 × 3--6 cm, base rounded to cordate, margins finely and sharply serrate or obscurely doubly serrate, teeth fine, sharp, apex acuminate; surfaces abaxially mostly glabrous, except sparsely pubescent along major veins and in vein axils, often with scattered, minute, resinous glands. Infructescences erect, ovoid to nearly globose, 1.5--4 × 1.5--2.5 cm, usually remaining intact for a period after release of fruits in fall; scales mostly glabrous, lobes diverging at or proximal to middle, central lobe short, cuneate, lateral lobes extended to slightly ascending, longer and broader than central lobe. Samaras with wings narrower than body, broadest near center, not extended beyond body apically. 2 n = 28.

Sweet birch grows primarily on three soil orders: Spodosols,  Inceptisols, and Ultisols. It grows best on moist, well-drained  soils but is also found on a variety of less favorable sites with  rocky coarse-textured or shallow soils (7). Because it is  occasionally abundant on rocky mountains in Pennsylvania, sweet  birch may be valuable for soil protection. On other poor soils,  however, such as the excessively dry portions of the Harvard  Forest in Massachusetts, sweet birch is partially or completely  replaced by oaks and conifers.

    Sweet birch grows over a wide range of altitudes  from near sea level along the New England coast to an upper  extreme of 1220 to 1370 m (4,000 to 4,500 ft) in the southern  Appalachian Mountains. In New England, the species is fairly  common in southern Maine, the highlands of New Hampshire, western  Vermont, the highlands of Massachusetts and Rhode Island, and  throughout Connecticut. In the southern Appalachians, where sweet  birch grows best, the optimum elevation is between 610 and 1370 m  (2,000 and 4,500 ft).

    Moist, protected northerly or easterly slopes are  considered most favorable for sweet birch in both northern and  southern parts of its range.

Precipitation in the range of sweet birch averages about 1140 mm  (45 in) a year, about half of it falling during the growing  season. In the northern part of the range, snowfall averages 200  to 250 cm (80 to 100 in) a year. Average annual temperature is  about 7° C (45° F) in the north and about 13° C  (56° F) in the southern Appalachians. The July average is 21°  C (70° F) in New England and 23° C (74° F) in the  southern Appalachians. Mean January temperatures are -9° to  -7° C (15° to 20° F) in New England and -1°  to 4° C (30° to 40° F) in the southern  Appalachians. The growing season varies from 90 to 220 days,  depending on latitude and elevation.

Rich, moist, cool forests, especially on protected slopes, to rockier, more exposed sites; 0--1500m.

Sweet birch is a minor species in 12 Society of American Foresters  cover types (3):

    19 Gray Birch-Red Maple
  20 White Pine-Northern Red Oak-Red Maple
  21 Eastern White Pine
  22 White Pine-Hemlock
  24 Hemlock-Yellow Birch
  25 Sugar Maple-Beech-Yellow Birch
  27 Sugar Maple
  28 Black Cherry-Maple
  39 Black Ash-American Elm-Red Maple
  57 Yellow-Poplar
  58 Yellow-Poplar-Eastern Hemlock
  59 Yellow-Poplar-White Oak-Northern Red Oak

    In the southern Appalachian region, sweet birch reaches its best  development in Types 21, 22, 25, 57, 58, and 59.

    Important associated tree species include  yellow-poplar (Liriodendron tulipifera), basswood (Tilia  spp.), white ash (Fraxinus americana), sugar maple  (Acer saccharum), red maple (A. rubrum), northern  red oak (Quercus rubra), white birch (Betula  papyrifera), gray birch (B. populifolia), hemlock  (Tsuga spp.), and eastern white pine (Pinus strobus).  Understory vegetation varies with locality, but commonly  associated shrubs are mountain maple (Acer spicatum), striped  maple (A. pensylvanicum), flowering dogwood (Cornus  florida), downy serviceberry (Amelanchier arborea), American  hornbeam (Carpinus caroliniana), and eastern hophornbeam  (Ostrya virginiana). Associated herbaceous vegetation  includes Solomons-seal (Polygonatum pubescens), marsh  blue violet (Viola cucullata), clubmosses (Lycopodium  spp.), mayapple (Podophyllum peltatum), trilliums  (Trillium spp.), jack-in-the-pulpit (Arisaema  atrorubens), and a variety of ferns. In former clearcut areas  where young stands are established, blackberry (Rubus spp.)  is abundant.

In northwestern Pennsylvania, glaze  storms have caused appreciable damage to crowns of sweet birch  trees. Available data indicate, however, that this species may be  rated as intermediate to fairly resistant to glaze in comparison  with other northern hardwoods and common associates (7). In  addition to the primary effects of ice damage in directly  reducing crown volume, glaze storms may contribute to the decline  and subsequent death of both yellow and sweet birches by allowing  wood decay organisms to enter or, possibly, by causing crown  deterioration from sudden excessive exposure.

    Sweet birch does not seem to be very susceptible  to winter killing. The severe winter of 1942-43 partly or  completely killed trees of many species in Maine, but sweet birch  appeared to be uninjured (7).

    A study of the effects of the 1930 drought on oak  forests in central Pennsylvania indicated that sweet birch is  intermediate in drought resistance. Drought caused mortality  reduced basal area by 36 percent, for sweet birch, 11 percent for  sugar maple, 50 percent for red maple, and 15 percent for white  ash (7).

    Several fungi attack living sweet birch trees, and  sterns frequently become highly defective at an early age. In  unmanaged sawtimber stands in the anthracite, region of  Pennsylvania, cull exceeded 20 percent of' the total cubic-foot  volume of trees 43 cm (17 in) in diameter on Site 1 and 23 cm (9  in) on Site II (7). The most important pathogens are, white trunk  rot (Phellinus igniarius), yellow cap fungus  (Pholiota limonella), and Nectria canker (Nectria  galligena) (5). Sweet birch is one of the most susceptible  species to Nectria canker. Cankers on the bole are more serious  than branch cankers because they reduce merchantable volume and  increase susceptibility to stem breakage.

    Sweet birch is easily damaged by ground fires  because it has extremely thin bark. Several fires may kill the  tree, but even light scorching at the base of the tree will lower  its resistance to the attacks of various diseases or insects such  as the ambrosia beetle (Xyloterinus politus) (9).

    Several leaf-feeding insects occasionally infest  sweet birch. The most prevalent ones are birch tubemaker (Acrobasis  betulella), birch skeletonizer (Bucculatrix  canadensisella), orientalmoth (Cnidocampa  flavescens), gypsy moth (Lymantria dispar), and dusky  birch sawfly (Croesus latitarsus) (6).

Sweet birch is classed as  intolerant of shade. A long, fairly dean bole is developed in  dense stands, while low, thick branches are produced on  open-grown trees. Sweet birch may seed in heavily after  clearcutting in the Appalachian region, but a majority of the  stems succumb to competition by age 20 (4). Sweet birch is one of  the species that has replaced American chestnut in stands where  chestnut was once a major component. Sweet birch has been  reported to occupy 15 to 20 percent of the basal area of  40-year-old stands in Connecticut (12), all-aged stands in  southwestern North Carolina (8), and 20-year-old even-aged stands  in West Virginia. In a 70-year-old even-aged stand in West  Virginia, 20 years of uneven-age management did not significantly  change the proportion of sweet birch, which remained at about  18 percent of the basal area of stems 13 cm (5 in) and larger in  diameter (13).

No informationavailable.

Flowering late spring.

Sweet birch has been known to  reproduce well from small stumps but seems to be less prolific  than many of its associates maple, sugar maple, beech (Fagus  grandifolia), yellow-poplar, and northern red oak.

Under forest conditions, seeds  normally germinate during the spring after they are dispersed.  Nursery experience indicates that germination may extend over 4  to 6 weeks. Germination is delayed when the embryo is dormant.  Moist mineral soils, rotten logs, and humus are suitable  germination media.

    In nursery practice, birch seed is usually sown in  the fall after collection in the late summer or fall. Seeds are  broadcast and covered as lightly as possible or not at all if the  seedbed is to be kept moist. Epigeal germination is usually  complete 4 to 6 weeks after sowing.

    Seedlings require light shade for 2 to 3 months  during the first summer. Tree percent is low; only 10 to 20  percent will produce 1-0 seedlings. Desirable seedling density is  270 to 485/m² (25 to 45/ft²). Usually 1-0 and 2-0  barerooted seedlings are planted (1).

    Sweet birch seedlings develop best during their  early years when protected by side shade or light overhead shade.  Scattered individuals frequently grow as advance reproduction in  openings in mature stands or under younger stands of light to  moderate crown density. In the Harvard Forest, sweet birch is  sometimes present in the advance hardwood growth under old-field  white pine about 50 to 70 years old (7). On fairly cool, moist  sites-sheltered ravines, north to east aspects, or moderately  heavy soils-heavy cutting or clearcutting of these stands  generally results in a higher proportion of sweet birch in the  succeeding reproduction than was present in the advance growth.  On the other hand, studies in northwestern Pennsylvania have  shown that clearcutting of immature second-growth northern  hardwood stands before an understory has developed is followed by  an abundance of intolerant species with only a poor  representation of sweet birch and tolerant hardwoods (7).

Seed fall is during  mid-September through November. Seed dispersal is normally by  wind and seeds may be blown some distance over crusted snow.  Nothing is known about quantities of seeds produced or how far  they are spread. Seed production begins when trees are about 40  years old; large seed crops are produced every 1 or 2 years.  Cleaned sweet birch seeds average 1,367,000/kg (620,000/lb) (1).

    Recommended storage conditions for birch seeds are 1 to 3 percent  moisture content at 2° to 3° C (36° to 38° F)  (1). Stratification does not generally improve germination, but  best germination is obtained when seeds are tested under light  (1).

Sweet birch flowers are  monoecious and borne in catkins. Staminate catkins are formed in  late summer or autumn and open in the spring after elongating to  about 20 mm (0.75 in). Pistillate catkins appear with the leaves  and are borne terminally on short, spurlike branches. Flowers  open in April and May. Seeds ripen from about mid-August through  mid-September and are contained in erect strobili (1).

Sweet birch saplings grow relatively  rapidly. The following data have been reported: In northwestern  Pennsylvania, at age 12, 1.8 m (6 ft) in height; in western  Pennsylvania and central West Virginia, at age 20, 14 m (46 ft)  in height and 10 cm (4 in) in d.b.h.

    On the very best sites, sweet birch grows 21 to 24  m (70 to 80 ft) tall and 61 to 152 cm (24 to 60 in) in d.b.h. In  most areas, however, it is a tree of medium size, 15 to 18 m (50  to 60 ft) tall and 61 cm (24 in) or less in diameter. One of the  largest trees on record is 147 cm (58 in) in d.b.h. and 21 m (70  ft) tall.

    According to a study in virgin hemlock-hardwood  stands in northwestern Pennsylvania, sweet birch saplings in the  understory grow about twice as fast as hemlock, beech, sugar  maple, and red maple slightly faster than yellow birch, and at  about the same rate as black cherry (Prunus serotina) (7).

    Data from plots on apparently average sites in  Delaware County, NY, and Forest and Potter Counties, PA, show  that sweet birch can attain a diameter at breast height of about  10 cm (4 in) in 20 years, 18 cm (7 in) in 40 years, and 25 cm (10  in) in 80 years (7). In unmanaged sites in the anthracite region  of Pennsylvania, sweet birch reached 36 cm (14 in) d.b.h. in 85  years on high sites (Site 1) and 30 cm (12 in) in 80 years on  average sites (Site 11). It is estimated that in managed stands,  the same sizes would be reached in 10 to 15 years less time (7).

    In the Pennsylvania anthracite region, periodic  cubic volume production begins to decline when the trees are 36  to 41 cm (14 to 16 in) in d.b.h. (7); that is, in about 100  years. Older trees are common and two individuals 192 and 265  years old have been found in Pennsylvania (7).

Sweet birch is closely related to yellow birch. Efforts to cross  the two species have been successful, but the F, hybrids have low  vigor and seed germination rates (11). No natural hybrids have  been verified.

    Virginia round-leaf birch, Betula uber, at  one time was classified as Betula lenta var. uber.  The known population of this species consists of 12 mature  trees, 1 sapling, and 21 seedlings in Smythe County, VA (10). In  1978, it was officially listed as an endangered species.

    A natural hybrid of Betula lenta and B.  pumila that occurred at the Arnold Arboretum was designated  B. jackii.

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 4
Specimens with Barcodes: 6
Species With Barcodes: 1

Canada

Rounded National Status Rank: N1 - Critically Imperiled

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Sweet birch wood is quite similar to yellow birch (2). Lumber and  veneer of the two species often are not separated in the market,  although production of yellow birch far exceeds that of sweet  birch. Sweet birch is used for furniture, cabinets, boxes,  woodenware, handles, and millwork, such as interior finish and  flush doors. Paper pulp made from sweet birch is used in various  amounts with other pulps to produce such products as boxboards,  book and newsprint paper, paper toweling, and corrugated paper.  Birch oil has been produced commercially from sweet birch bark,  but its use has declined with the introduction of synthetic  products.

Betula lenta is a dominant tree in the northern hardwood forests of the northern Appalachians and a valuable source of timber. It was formerly the chief commercial source of wintergreen oil (methyl salicylate), which is distilled from its wood. Betula lenta is most easily separated from B . alleghaniensis by its close bark and the glabrous scales of infructescences. 

 Native Americans used Betula lenta medicinally to treat dysentery, colds, diarrhea, fevers, soreness, and milky urine, and as a spring tonic.