Pinus thunbergii, the Japanese black pine tree

Along the coastal beaches and low mountains of Japan lives a stout and elegant pine species, Pinus thunbergii. This iconic Japanese tree is known for its beauty as a garden specimen, as a bonsai subject, and also a protector of coastline communities throughout the country. It also is well known the world over as Japanese black pine, a versatile and resistant tree, but also a plant with disease issues. It is a lovely tree regardless, and Japan’s gardens and coastlines wouldn’t be the same without its resolute presence.

Pinus thunbergii is a large coniferous tree growing to 40 meters under good conditions, but is usually much smaller, particularly when growing on beach dunes, a common habitat for this tree. Specimens found at some Japanese shrines can be even taller with the tallest on record being an incredible 66 meters! This tree often sports a broad dome shaped crown on very old specimens. The bark is silvery to black and deeply fissured. The evergreen needles come two per fascicle (or bundle), are a dark green and up to 12 cm long. Healthy trees are densely needled and bushy looking, especially when young. Pollen cones appear in early spring, are conical and elongate and orange-yellow in color. The seed cones initiate at the same time starting out a rich magenta, and grow in size as they mature over the summer and are nearly round at maturity. Seed is released in winter.

This tree is widespread on or near the coasts of the warmer parts of Japan on Honshu, Shikoku, and Kyushu islands. It is also found in South Korea. It grows most commonly along seashores starting just behind the newest line of dunes and extending inland for a kilometer or more forming the bulk of the canopy of such forests. More inland it prefers rock outcrops and dry ridge-lines in the mountains up to a 1000 meters or more elevation. On occasion it occurs on dry rock barrens in the mountains. Where this species is found in mixed stands with Japanese red pine, Pinus densiflora, the unusual hybrid called akakuromatsu (red-black pine) sometimes results (known under the Latin name, P. x densi-thunbergii). These hybrids have the red bark of P. densiflora while retaining the darker, more stout needles of P. thunbergii.

This is the famous Japanese black pine tree that has been planted throughout much of the temperate world. Historically it was an important lumber species, but these days forests are highly diminished in size, so they are rarely used for building material anymore. It’s wood was traditionally used to build shrines in Korea in particular.

This tree is remarkably resistant to harsh conditions whether it be cold winter winds, salt spray, drought, and or low nutrient soils. For centuries Japanese black pine has been used to make bonsai and to this day amazing examples exist not only in Japan, but anywhere enthusiasts grow them. It is also a common garden subject in Japan where it is invariably pruned into dwarf forms much like bonsai, but on a much larger scale. Due to the tree’s naturally long needles, dwarfed trees need have their needles pruned and thinned on an annual basis to reduce their overall length, thus insuring a more natural proportion between them and the trunk and branches. The beauty of a well pruned tree is beyond words.

The coastal forests this tree occupies have been long recognized as an important aid in keeping beach erosion in check as well as acting as a buffer to strong winds and tidal surge from the sea including typhoons that haunt these shorelines in summer and early fall. In the low coastal mountains it is found in loose groves usually near rock outcrops or on rocky ridges where drainage is excellent. I have also found it growing in rocky barrens in the mountains where the soil is little more than highly weathered rock. The growth rate of such trees is slow and a typical specimen in these places is rarely much more than a couple meters tall, much like the trees of some mountain populations of Pinus rigida in the northeastern USA.

In recent times coastal populations have been under attack by the North American pinewood nematode, Bursaphelenchus xylophilus, as well as blue stain fungus, (the most commonly cited species being Ophiostoma minus, but others exist). Add to that the effect of certain pine bark beetles that literally girdle the trees, and this species is in deep trouble in its native homelands. Currently scientists are working on genetically engineering stronger trees and these are being tested at sites all over Japan. Thousands of freshly planted Japanese black pine seedlings on or just behind coastal dunes is a common sight these days along Japan’s shores. With luck these efforts will be successful and this noble tree will continue to grace coastal forests for years to come.

The species epithet, thunbergii, is in honor of Carl Peter Thunberg (1743-1828), a Swedish botanist and physician who was fortunate enough to be allowed to visit Japan during the Edo Period (1603-1868). During his stay he described many of Japan’s plant species (along with many Chinese transplants and in error labeled them “japonica”) and became known as the “Japanese Linnaeus” after his mentor and the inventor of the Latin based binomal nomenclature system used to this day in identifying organisms. One of the more interesting things he did during his visit was to introduce a new cure for syphilis while in the capital city, Edo (now Tokyo). His popularity grew with this impressive and highly needed gift! The Japanese name for P. thunbergii is kuromatsu from the words kuro meaning “black” and matsu, “pine” – rendering the straightforward name “black pine” in English.

While this tree is one tough customer, it has its share of problems, not the least of which are the above mentioned disease issues. Beyond that, it is not too challenging to grow as long as the roots aren’t water logged. It will grow in just about any free draining, acidic soil. Like most pines it requires full sun to grow well. A bonus feature is its wide range of temperature tolerance being able to handle extreme heat in summer and cold, dry, and even salty winter winds. It also is resistant to high levels of air pollution, and so thrives in urban environments as well.

It is probably happiest in USDA zone 7-8, but can be grown from zones 6-9 so long as summer temperatures get fairly high and winter averages are below 10 C (50F). The natural hybrid of this species and P. densiflora, P. densi-thunbergii, is considered a good omen and so is planted in gardens throughout Japan.

In a genus that boasts some of the world’s most impressive conifer species, P. thunbergii holds its own in such company admirably. This iconic tree is beloved by many and for good reason – it is both lovely and resilient. That is reason enough for its survival into the future via the maintenance of remaining coastal forests, and its use as a garden plant the world over.