Betula costata is a deciduous tree notable for its peeling, chalky white bark that reveals a salmon or cinnamon underlayer. This handsome birch displays ovate, toothed leaves turning golden yellow in autumn. Thriving in cool climates, it stretches upwards to reach light, often growing in mixed forests where its distinct bark and vibrant fall foliage stand out among greenery.
I. Appearance and Characteristics
Betula grossa, commonly known as Japanese cherry birch (Japanese: 梓 azusa), is a species of birch native to Japan, where it grows naturally in mixed woodland on hill and mountain slopes in Honshu, Shikoku , and Kyushu. It was introduced to the West in 1896, but remains rare in cultivation.
Betula grossa is conical in outline, but its most distinctive feature is its cherry-like bark, with horizontal stripes of reddish-grey becoming dark grey with age, exfoliating in thin papery curls. The dark green leaves are up to 10 cm long and turn golden-yellow in autumn. The shoots are aromatic, and carry long, yellow-brown, male catkins in early spring. The species is considered closely related to the American birch Betula lenta.
II. How to Grow and Care
Sunlight
The perfect location for betula costata receives 6-8 hours of sunlight with shaded, cool soil. This is very important, as betula costata has a relatively shallow root system and is thus sensitive to soil overheating or drought.
If you’re in the northern hemisphere, the perfect spot for betula costata cultivation is between the northern and the eastern side of a house, where the building can provide afternoon shade. Avoid western and southern sides, as the strong afternoon sun can dry the soil and negatively affect the tree’s root system. Keep in mind that existing trees and other structures can provide afternoon shading. (If you’re in the southern hemisphere, plant on the opposite side).
Temperature
Betula costata needs plenty of water and is somewhat sensitive to extreme moisture fluctuations. Most plants in genus Betula are adapted to temperate (and some species to moist) climates. Most of them grow best on moist but not wet soil. Avoid planting your tree in areas that are poorly drained or occasionally flooded, even for short periods.
Watering
Newly planted betula costata can be sensitive to too little or too much water, so watering 30 seconds twice a week should be enough. The important thing to keep in mind is that the soil should be moist, which means not too dry or soaking wet. Once the tree is established, there is no need to water, except in a hot summer. In summer, lay a hose on the base of the tree and water in a mild stream, allowing water to slowly run over the root system.
Soil
Plant betula costata in an area with acidic soil protected from compression. It develops a shallow root system that can be easily damaged by soil disturbance. It is very important to choose a good planting site and avoid areas prone to soil compression, such as driveways or pathways. Avoid wet soils that harm the root.
Plants in genus Betula grow best on somewhat acidic soils, with pH of 5.0-6.5, although this can vary from species to species. For example, the white-barked birch, such as paper birch (B. papyfera), can grow on alkaline soils. On the other hand, river birch (B. nigra) will likely show symptoms of iron chlorosis (yellow coloration of the leaves) in alkaline soils. Avoid planting any river birch in soil with a pH higher than 6.5.
Test your soil before you select your birch species (soil tests are available for purchase at most tree nurseries). If the tree has already been planted in soil that is slightly more acidic or alkaline, the soil can be amended. However, it can be complicated and expensive to keep these levels throughout the lifespan of a tree.
Fertilizing
If the soil is alkaline or lacks certain nutrients, fertilize every spring and summer. Most species grow best in somewhat acidic soils with a pH value between 5.0 and 6.5. Slow-release fertilizer should be used. Fertilizer spikes are convenient and simple to use. However, you should fertilize only after a soil test determines that the substrate is lacking in nutrients.
Fertilize in early spring or summer, as this is the peak growth period when a tree requires the most nutrients. Avoid fertilizing the tree in mid-fall, as a late flush of growth may not harden before the winter and expose the young tissue to frost damage.
Planting Instructions
The planting location should ideally provide 6-8 hours of sunlight daily, while keeping the soil shaded, cool, and moist. The tree should be planted in a square-shaped hole 25 cm deeper than the tree’s root ball. A young tree should be supported by tying it (not too tightly) to a wooden stake or rebar with a rubber or a nylon band.
Pruning
Betula costata should not be pruned in late winter or early spring just before its dormancy period ends. This is because heavy sap flow and open wounds attract birch tree borers in their egg-laying season. Removing more than 25% of the total tree canopy will most likely result in tree death or seriously reduced growth, as with lost photosynthetic surface, the tree loses the ability to synthesize its nourishment. Also, removing too much of the canopy can expose the tree base and roots to too much sunlight.
Prune your betula costata in late summer or early winter. If performed properly, pruning is very beneficial, as removing dead or infected branches, closely growing branches, and branches protruding out of the canopy increases the overall health of the tree, reduces tree infections, and improves the aesthetic appearance. Remember to disinfect the pruners before you move to the next branch in order to minimize the risks of contamination.
III. Uses and Benefits
Another signature bark characteristic is its habit of separating into thin sheets; Native Americans used this property to harvest the bark from fallen paperbark birch trees to make canoes, bowls and shelter — practical as well as beautiful.
