Japanese cedar, Cryptomeria japonica v. japonica

Japan’s forests are home to a massive tree species – this country’s answer to a redwood.  It is the famous Japanese cedar, Cyrptomeria japonica, but better known as sugi in Japan.  This tree is both beloved and at the same time nearly despised in modern Japan for reasons this article will make clear.

Cryptomeria japonica var. japonica (hereafter called simply C. japonica) is a massive evergreen coniferous tree reaching 50 meters or more high – some are said to be 70 meters, an almost unimaginable height for these typhoon swept islands.  Likewise, its trunk girth is gargantuan, up to 10 meters or more in some specimens with the limit being around 16 meters.  The bark is reddish brown to silvery, growing in strips.  In young trees these can flake off, but older trees have more compact bark that is thicker in substance.

The branches grow in a whorl up the trunk and tend to hang down a bit.  Young trees are nearly conical in shape, but old trees have irregular branching, more pendulous branches, and tend to be rounded at the top.  It is not uncommon to see multi-trunked specimens and ones that have saddle like branches – all the product of storm damage in their past.  In old specimens the lower trunk can be branch-less for 10 or more meters.

Japanese cedar leaves are light green to bluish green, needle like in appearance and either hang down or grow upward in loose clusters.  They tend to break off in large pieces when they fall rather than falling apart on the tree.  As a consequence, the forest floor is littered with their leaf clusters and small branches, sometimes to a depth of 15 cm or more.  Their foliage commonly “bronzes” in cold weather, so sugi forests can look red brown in the winter months.

The pollen cones (male) and seed cones (female) are born separately, but on the same tree (monoecious habit).  The yellow-brown pollen cones grow in bunches on the outermost twigs and are roughly conical shaped and are only a centimeter or so long each.  The seed cones start out growing bright green and eventually turn a rich brown at maturity.  The male cones release their pollen starting in February in Kyushu and perhaps until May further north.  In pollen season the air can literally be filled with sugi pollen, much like a dust storm.

C. japonica ranges throughout the warmer parts of Japan.  The variety sinensis is found in China.  No variety is listed as native to Korea, which is surprising given that Korea, China, and Japan have been connected many times in past glacial periods.  It prefers wet to moist woodlands, along mountain streams and seepage slopes, but also can be found on exposed ridge-lines, from 0 to 1000+ meters elevation.  Trees can be in mixed stands with other conifers or most often with broad leaf trees, both deciduous and evergreen.  Pure stands are known to occur, but this may be an artifact of human planting in the distant past.

This is one of the most distinctive Japanese trees.  For one thing, it is the tallest and most massive tree species in Japan being a close relative to redwoods and sequoias.  Culturally it is also significant in several ways. It is the national tree of Japan and large specimens are often seen at temples.  Many of these are considered to house a god (kami).  It also is one of the most important timber species in the country, especially in the south.  Sugi plantations can be seen on almost any mountain here.  After WWII a massive program was instituted to reforest Japan’s mountainsides. Both sugi and hinoki (Chamaecyparis obtusa) were widely planted in this effort.  A negative effect that was not considered was that during pollen season people would end up suffering, and suffer they do.  In late winter and early spring millions of people have to endure weeks of hay-fever brought on by the clouds of sugi and hinoki pollen coming off the mountainsides.  Since Japanese cedar is an important lumber tree, it is likely that plantation forests will continue to be maintained into future, despite this problem.

Another negative aspect of these forests is the lack of biological diversity in them.  If you spend some time in these plantations you’ll soon see that only a relatively few species of plants can live in them successfully.  Neither sugi nor hinoki, particularly younger trees planted en-mass, provide much food or habitat for most wildlife either.  Since the age of the trees is essentially even, competition for space and light is at a premium, and makes it nearly impossible for other tree species to take hold.  Some of these forests are thinned so that the remaining trees can grow better.  This may help some ground dwelling herbs and a few kinds of opportunistic woody species, but by and large few animal or plant species benefit from them.  Of the native orchids, only Liparis nervosa v. bituberculata seems to actually prefer these places, and while a handful of others seem to be able to persist, none of them thrive.

A far more rare sugi forest is a mature stand of old growth trees.  These stands are found throughout its range, but represent a very small area in comparison with the plantation forests.  The most celebrated sugi trees are found on Yaku Island just south of Kyushu.  Here grow the largest sugi in the world, the so called yakusugi, with the Jomon Sugi being the most celebrated.  Speculation about the age of these ancient trees varies widely, but the most likely number would be between 1000-3000 years old.  A more local stand of old growth sugi grow within a short drive from my front door on Wakasuiyama (Young Cedar Mountain).  This forest contains trees in excess of a thousand years old and there are many that are centuries old.  The biggest tree stands 40 meters tall and is 16 meters in circumference around the base, however the tree splits into five stems a couple meters up the trunk.

In this video you can see some big sugi growing on a local mountain in the Fukuoka City area, Wakasugiyama:

This forest has little resemblance to the surrounding plantations.  Not only are the sugi trees older and bigger, but the forest itself is far more diverse with a wide range of other trees present.  Likewise, the sub-canopy forest and forest floor communities are very diverse as well.  Such systems provide habitat for a bewildering range of plants, insects, fungi, and of course animals. Part of the explanation for this is that trees are widely spaced and uneven in age and size.  This provides room for other species without any particular one dominating.  The forest floor is bright as opposed to the dim light of thick plantations, even sunny in spots.  Also, with the great variety of plants growing here, the range of habitats for all wildlife is much higher, and there is an abundance of food resources.  It is unfortunate that such forests are so rare today, but they will always have a place in Japan, and so serve as refuges for rare biota.

Japanese cedar is widely grown throughout warm temperate to cool temperate climates the world over.  Many cultivars have been isolated, some being very dwarf forms less than a meter tall and others becoming full blown trees.  It seems to do well in a wide range of soil types, but is no doubt sensitive to truly basic soils.  Also, it is drought intolerant, needing a steady supply of water throughout the year.  It probably will not thrive in climates that are low in humidity or experience cool conditions year round.  These trees like warm to hot summers with ample moisture, but just as surely prefer cool winters.

C. japonica should be able to grow in USDA zones 6 through 9a no problem, but hardiness in cooler climates could prove unreliable.  Dwarf forms can be protected in winter, and so might survive colder winters if sited well.  In the southeast USA trees are subject to a needle blight (Cercosporidium fungus), and may lose their attractiveness in time.  The variety sinensis is commonly grown in China as a timber species.  It is interesting to note that it has also been grown in Hawaii as a timber tree since the 1880’s and may be invasive in some ecosystems there.

A true giant of Japan’s southern forests, this tree remains both materially and symbolically a living part of this country.  Seeing an ancient tree up close is a memory that won’t easily be forgotten.  To live so close to these ancient trees, full of the memories of centuries, indeed millennia, past, is a privilege exceeding my short life.  I can’t help but wonder what secrets they hold.