Species of the genus Betula are a difficult group taxonomically because of their high vegetative variability and frequent hybridization. Many species have been founded on only slight differences and many of these have subsequently been reduced to synonymy. Many morphologic and cytologic studies have attempted to deal with variation within the genus or its subgroups. Species of Betula form a polyploid series, with chromosome numbers of 2 n = 28, , , , and 112, plus additional numbers in some hybrids.

Common Name: River Birch

General Information

Betula nigra is a deciduous tree with a round crown; it can grow up to 25 metres tall. The tree often produces several trunks from low down[, ].
The tree has a wide range of traditional uses as a food, medicine and source of materials. Cultivars with freely exfoliating bark are commonly cultivated as ornamentals in the Northeast and Midwest[].
Betula nigra is a commonly encountered tree species near permanent water. The species has a wide distribution across the United States of America. There are no known threats that are or will adversely affect this species in the foreseeable future. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

, ,

Range

Eastern N. America - Minnesota to New Jersey, south to Texas and Florida

Habitat

Banks of streams, by swamps etc, in deep rich soil that is often inundated for weeks at a time[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Ornamental, Wild

Cultivation Details

This species at its northern geographic limit coincides with a growing season of 150 days or less with an annual average precipitation 760 mm (30 in). It is most abundant in the southeastern United States where summers are very hot and humid with a growing season of 210 to 270 days with an annual average precipitation 1,270 mm (50 in)[].
Succeeds in a well-drained loamy soil in a sheltered position11, , ]. Grows well in heavy clay soils. Likes its roots within reach of water[]. Dislikes wet soils according to another report[]. Shade tolerant[].
Hybridizes freely with several other members of this genus[, ].
A good plant to grow near the compost heap, aiding the fermentation process[].
Species in this genus are notably susceptible to honey fungus[].

Edible Uses

Sap - raw or cooked[]. A sweet flavour[]. Harvested in early spring, before the leaves unfurl. The trunk is tapped by drilling a hole about 6mm wide and about 4cm deep. The sap flows best on warm sunny days following a hard frost. It makes a refreshing drink[, ] and can also be concentrated into a syrup or sugar[]. The sap can be fermented to make birch beer or vinegar[]. An old English recipe for the beer is as follows:-
'To every Gallon of Birch-water put a quart of Honey, well stirr'd together; then boil it almost an hour with a few Cloves, and a little Limon-peel, keeping it well scumm'd. When it is sufficiently boil'd, and become cold, add to it three or four Spoonfuls of good Ale to make it work...and when the Test begins to settle, bottle it up . . . it is gentle, and very harmless in operation within the body, and exceedingly sharpens the Appetite, being drunk ante pastum.'[].

Medicinal

A salve was made by boiling the buds until they were thick and pasty, sulphur was added and this was then applied externally to skin sores and ringworm[].

The leaves have been chewed, or used as an infusion, in the treatment of dysentery[].

An infusion of the bark has been used to treat stomach problems, 'milky' urine and difficult urination with discharge[].

Agroforestry Uses:

This species has an extensive root system and is sometimes planted for erosion control along the banks of streams[].
It is an important mine reclamation species due to its tolerance to acid soils[].

Other Uses

Young branches are used to make besoms, whisks etc[].

The wood is light in weight, strong, close grained and hard, but it contains many knots because of the numerous branches along the trunk. It weighs 36lb per cubic foot. Of little use commercially, though it is sometimes used for furniture, turnery etc[, , , , ].
The wood of Betula nigra is not in high demand for timber because of its generally poor quality[].

Propagation

Seed - best sown as soon as it is ripe in a light position in a cold frame[, , , ]. Only just cover the seed and place the pot in a sunny position[, , ]. Spring sown seed should be surface sown in a sunny position in a cold frame[, ]. If the germination is poor, raising the temperature by covering the seed with glass can help[]. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in a cold frame for at least their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts.
If you have sufficient seed, it can be sown in an outdoor seedbed, either as soon as it is ripe or in the early spring - do not cover the spring sown seed. Grow the plants on in the seedbed for 2 years before planting them out into their permanent positions in the winter[, , , ].