Japanese larch (Larix kaempferi) is an attractive conifer that often graces large gardens, parks, and public spaces. However, this is also a popular species in bonsai and several dwarf cultivars exist that are better suited to smaller gardens. The tree’s wood is strong and long-lasting and is used for construction and fencing. The specific epithet, kaempferi, honors German naturalist Engelbert Kaempfer.
I. Appearance and Characteristics
Larix kaempferi, the Japanese larch or karamatsu (唐松) in Japanese, is a species of larch native to Japan, in the mountains of Chūbu and Kantō regions in central Honshū.
It is a medium-sized to large deciduous coniferous tree reaching 20–40 m tall, with a trunk up to 1 m diameter. The crown is broad conic; both the main branches and the side branches are level, the side branches only rarely drooping. The shoots are dimorphic, with growth divided into long shoots (typically 10–50 cm long) and bearing several buds, and short shoots only 1–2 mm long with only a single bud. The leaves are needle-like, light glaucous green, 2–5 cm long; they turn bright yellow to orange before they fall in the autumn, leaving the pinkish-brown shoots bare until the next spring.
The cones are erect, ovoid-conic and 2–3.5 cm long, with 30–50 reflexed seed scales; they are green when immature, turning brown and opening to release the seeds when mature, 4–6 months after pollination. The old cones commonly remain on the tree for many years, turning dull gray-black.
It grows at altitudes up to 2,900 m on well-drained soils, avoiding waterlogged ground.
The scientific name honours Engelbert Kaempfer. It is also sometimes known by the synonym Larix leptolepis.
II. How to Grow and Care
Japanese larch is a deciduous conifer with specific seasonal care requirements. It thrives in full sun and well-drained, slightly acidic soil. A special care point for japanese larch is the need for adequate space to accommodate its mature size. Regular watering is critical during the formative years, while mature trees are more drought-tolerant. Monitoring for typical pests such as larch casebearer is also essential.
Sunlight
Japanese larch thrives in conditions of full sun, requiring bright, unfiltered light for optimum growth. While japanese larch is adaptable to a range of light exposures, prolonged periods outside of its ideal intensity can lead to suboptimal development and reduced health. Full sunlight encourages robust growth and maintains the plant’s vigor. Specifically, the preference for direct light means japanese larch does best in open outdoor landscapes, away from the shade of taller vegetation. Such light conditions promote healthy photosynthesis, essential for japanese larch’s lifecycle as a deciduous conifer, particularly in its preparation for dormancy in colder seasons.
Watering
Originating from mountainous regions, japanese larch is accustomed to a moderate moisture regime, reflecting its ability to withstand periods of low water availability. It thrives with a balance of hydration and drainage, showcasing drought tolerance once established. Watering for japanese larch should be consistent with a schedule of once every 1-2 weeks. As an outdoor deciduous conifer, japanese larch’s watering needs fluctuate with the seasons; less frequent during dormancy in winter and increased during the active growth phase in spring and summer.
Soil
Larix kaempferi prefers a well-drained porous gravelly subsoil, overlaid with a light sandy loam. They seem to be particularly happy in a soil underlaid with a porous glacial drift. In cultivation, however, they succeed very well in ordinary well-drained soil. When the plants are set in clay soil, which is often done, the soil should be thoroughly loosened by trenching or subsoil plowing, and well under-drained. Any available humus, wood ashes, and well-rotted manure incorporated in the soil greatly aid in rendering it friable and porous for the roots.
Manures and mulches
Mulching with ordinary well-rotted barnyard manure in late autumn affords much stimulus to growth. By the following spring the manure will be in a desiccated condition and can be incorporated with the soil. A heavy mulch of old straw, rotten hay, or any similar material over the roots, and this was maintained throughout the entire growing season is beneficial to the plants in a more or less juvenile condition.
In many cases manure is not obtainable. In such an event, newly moved plants should be heavily mulched with rotten straw, rotten hay, or any similar rubbish for a few years until they become established. The frequent stirring of the ground over the roots subsequently will conserve sufficient moisture.
An area extending from the stem to one to two feet beyond the branches, stirred up with hoe and rake perhaps five or six times throughout the growing season, is very beneficial in conserving the moisture around the roots.
Pruning
Removal of the lower branches of Japanese larch is a serious mistake, and, if healthy, they should be retained to the base. Pruning or disbudding can be intelligently performed to add much to the natural symmetry. The extraction or removal, early in spring, of the central or terminal bud, will tend to compel the branches which start from the side buds to spread apart and form a much denser growth. Cutting back the previous year’s terminal growth to a strong bud or branchlet on the main limbs over the tree, if the plant is inclined to be thin in its branching, always produces a much denser lateral growth.
Propagation
Japanese larch is effectively propagated via grafting, which involves fusing a scion from a mature tree to a compatible rootstock to ensure genetic consistency and vigor. Gardeners should select a healthy scion and rootstock, make clean cuts for a strong union, and maintain adequate moisture and temperature conditions to encourage successful graft take and growth. Focused care in the early stages of development will help japanese larch achieve a robust start.
Transplanting
Transplanting can be done at all times of the year, excepting midsummer when they are in full growth. The best success is secured in spring when the buds begin to swell. From the end of August to the middle of September, if there have been abundant rains and the ground has been well soaked, is a very good time to move the plants. They may be planted late in autumn when circumstances compel it, but there is likely to be a considerable percentage of loss. Their roots are very susceptible to injury from exposure to the air, and the utmost vigilance should be exercised to keep them covered and moist.
III. Uses and Benefits
Japanese larch is an important tree in forestry plantations, being grown throughout central and northern Japan (north to Hokkaidō), and also widely in northern Europe, particularly Ireland and Britain. The wood is tough and durable, and is used for general construction work. Small larch poles are widely used for fencing.
