Sweet birch (Betula lenta), also commonly called cherry birch or black birch, is a striking species of birch tree that is characterized by shiny black-brown bark and foliage that turns bright yellow in the fall months. Indeed, it is considered to have the best fall color among all of the birch species. Similar to cherry trees, the bark on mature sweet birches becomes plated due to vertical cracks forming.
Nearly every part of a sweet birch can be harvested and used. The leaves, twigs, and inner bark of a sweet birch have a strong wintergreen scent and are used in the production of oil of wintergreen, and the sap can be used for boiling syrup (similar to the Sugar Maple) as well as in the production of birch beer. Sweet birch wood is also harvested and used for crafting furniture, flooring, and more.
|Botanical Name||Betula lenta|
|Common Name||Sweet birch, black birch, cherry birch|
|Plant Type||Tree, deciduous|
|Mature Size||40-70 feet tall|
|Sun Exposure||Full sun|
|Soil Type||Moist, well-drained|
|Soil pH||< 6.8|
|Flower Color||Green (catkins)|
|Native Area||Eastern North America|
How to Grow Sweet Birch
Sweet birch is native to eastern North America, occurring naturally in areas from southern Maine to southernmost Ontario, and south from the Appalachian Mountains to northern Georgia. They occur on moist woodland slopes and grow well in rich, high-quality soils with plenty of light. They require little maintenance other than some annual pruning and attract plenty of wildlife including bees and other pollinators, songbirds, grouse, small mammals, deer, and even moose. In April and May, sweet birches produce fruiting catkins that ripen in the fall and contain many small seeds that are distributed by the wind in the winter. Sweet birch is notorious for seeding at a prolific rate, and often overtake areas where other tree species have been wiped out by pests or disease.
When grown in the right conditions, sweet birches have a moderate growth rate of approximately 20 feet every 20 years, typically topping out at 50-70 feet tall. Stunted growth and a more shrublike appearance are both indications that a sweet birch tree is struggling and is not growing in its ideal conditions.
Sweet birch grows best in bright, direct sunlight. At least six hours of direct sunlight per day is sufficient for sweet birch.
Sweet birch trees prefer rich, fertile soil that is slightly acidic, well-draining, and moist. While they can tolerate soils with poor drainage, they likely will not thrive. Sweet birch trees cannot tolerate dry conditions and will not be able to grow in dry, poor quality soils.
Sweet birch trees grow well in wet conditions and are not drought-tolerant. When grown in moist soil in areas that receive regular rainfall, supplemental watering should not be necessary. However, if you live in a dry region you may need to water your sweet birch between rainfalls to ensure it does not dry out.
Temperature and Humidity
Sweet birch trees are hardy in zones 3 to 7 and tolerate cold temperatures well. Sweet birch trees do not tolerate heat well and as a result, they do not grow well in zones 8 or higher. The cold winter and spring temperatures in zones 3 to 7 also make sap production and harvesting possible for sweet birch as their sap flows freely once nighttime temperatures stay above freezing (a later harvest than sugar maple sap).
Generally, sweet birch trees do not require regular fertilizing as long as they are growing in nutrient-rich soil. However, there are some situations in which fertilizing your birch tree can be beneficial. For example, fertilizing young sweet birch trees in the spring or fall can help them grow more rapidly. If your sweet birch is growing in nutrient-deficient soil, regular fertilizing can also be done to correct the nutrient deficiencies. A low-nitrogen fertilizer, such as an 11-22-22 formula is best for sweet birches.
Sweet birch trees benefit from regular pruning as with most tree species. Do not prune sweet birch trees until at least the summer months to ensure the sap has stopped flowing. Another benefit of pruning in the summer or fall is that you will avoid the egg-laying season for several tree pests that infest the open pruning wounds.
When pruning birch trees you want to be as conservative as possible. Generally, removing 25 percent or less of a tree’s canopy is a good rule for pruning as removing more than 25 percent of the canopy can weaken the tree. Cut branches back so that there is no remaining stump and the cut is flush with the collar of the tree. Disinfecting your pruning tools between each branch will help to keep the tree healthy and the pruning cuts free from disease.
Unfortunately, birch trees are susceptible to a number of common pests and diseases. Birch leafminers and bronze birch borers are the two most pervasive birch tree pests. Birch leafminers feed on the leaves of birch trees, eventually causing brown leaves and leaf drop. While they don’t kill birch trees, they weaken their resistance to other pests and diseases, particularly the bronze birch borer which can kill birch trees. Unlike the birch leafminers that just feed on the foliage of birch trees, bronze birch borers burrow beneath the bark and feed on the vascular tissue of the trees which damages their ability to transport nutrients to the leaves. Sweet birch trees have intermediate resistance to bronze birch borers compared to some other birch species but can still become infected if the borers are particularly vigorous. As such, yellowing leaves at the top of birch trees is usually the first symptom of a bronze birch borer infestation. In addition to these two pests, birch trees are also susceptible to a number of diseases including leaf spot, canker, dieback, wood-decay, and mildew.