Moso, Japan’s giant bamboo, Phyllostachys edulis

Japan is home to many iconic plants, for example the Japanese plum tree (Prunus mume), and the red spider lily (Lycoris radiata). The odd thing is that neither of these species is native to Japan, but rather are imports from China. Moso bamboo (Phyllostachys edulis), another Japanese icon, shares their fate. If that weren’t enough, being in truth a very large grass, moso cannot be considered a tree either, despite its arboreal size. Regardless of these facts, moso remains the most important timber bamboo in the world, and has a central role in Japan’s traditional culture, ranging from construction material to food.

Phyllostachys edulis is a large growing bamboo with stems (called culms) routinely attaining heights of 15 meters or more, indeed reports of culms approaching even 30 meters exist in its most favored habitats. Being a “giant” or “timber” bamboo, culm diameter can be impressive, up to 20 cm, but as little as 8 cm in weaker culms.

Like other bamboos, the nodes on the culm are very easy to see, forming a segmented stem that is hollow inside except at the node itself. The culms are not tapered, but rather columnar in structure, only tapering near their apex. The uppermost nodes have one or more side branches that in turn bear the numerous elegant, small leaves. Culms fully mature within two seasons growth and can last up to 12 years.

The paper thin leaves are plentiful and last one growing season, each usually 4-10 cm in length and less than 2 cm in width. In Japan they turn yellow all at once in May and are shed in time with new culm formation. The bright green, new leaves on the old culms grow quickly and are fully developed by June. Branching on the old culms becomes more intricate over time, hence more and more leaves are held by any given culm as they age, thus increasing their beauty and photosynthetic potential.

The culms originate from underground shoots that are born off a highly complex mat of segmented rhizomes that tend to grow fairly shallow in the substrate, typically not more than a half meter deep. On moister sites it is not uncommon to see them growing along the surface of the ground here and there. These rhizomes are stolon-like, extending in all directions, thus making this a “running bamboo” species. The white roots too, are numerous and strong.

New growth shoots break ground in spring once the average air temperature reaches 18-20 C, usually in mid to late April in southern Japan. At first they grow slowly, but once they attain a height of 1 m or so, they rocket into growth, literally. It is well documented that this species is one of the fastest growing plants in the world, having been “clocked” at 1.2 meters of growth in just one day!

The emerging shoots are covered in alternating, hairy dark brown sheaths that are tipped with green, leaf-like projections. These sheaths cover the developing culm as it rockets upward, but just as quickly are shed, starting from the bottom most segments, revealing the new blue-green culm underneath. Remarkably, the culm is fully grown within 5-6 weeks and will begin to harden off, a process that takes more than one growing season. It will never get any taller or thicker however since its anatomy has no means to do this. One has to remember this is indeed a grass, not a woody plant.

Flowering cycles are not predictable, and occur only rarely, perhaps every 50 to 100 years. The old idea that bamboo dies en mass after flowering does not seem to hold with this species. Rather, an odd patch of culms will flower here and there. I have never seen large areas of moso dying back for any reason, but then again, I cannot remember having ever seen them in flower either. It is said that seed production is poor in Japan, with some flowerings producing no viable seed at all.

This massive bamboo can be found throughout the warmer parts of Japan, from Hokkaido’s southernmost islands, across Honshu in warmer and lower elevations, throughout Shikoku and Kyushu, and onto the Nansei Island chain. Its preferred habitat is on or near low hills in warm temperate regions that have been disturbed by human activity, for instance near rice fields and in Japanese cedar (Cryptomeria japonica) and hinoki cypress (Chamaecyparis obtusa) plantations. While it favors moist sites, it is commonly seen clinging to steep hillsides, sometimes falling prey to landslides during the summer monsoon. This species also can be found in Korea, Taiwan, and of course in the warmer parts of mainland China, where it is native.

Moso is so widespread these days in Japan that it is hard to believe it isn’t a native species. In fact its history here is rather brief, extending back only to 1736 (some sources cite 8 years earlier) when it was brought from China by the Satsuma Clan in what is now Kagoshima Prefecture in southern Kyushu. Its spread in the intervening years was by human hands however, rather than through natural reproduction. The reasons for its wide distribution are simple, it was and to some extent still is, an important plant to Japanese culture and thus was planted virtually anywhere it could grow, serving as a dependable natural resource. Moreover, due to the plant’s odd and irregular flowering cycle, it never would have left Kagoshima if humans hadn’t helped.

Due to its aggressive roots and running rhizomes, moso quickly takes over large areas once established. It has been known to colonize abandoned rice patties, something commonly seen on terraced hillsides. More disturbingly, it is replacing forest, especially on Kyushu, since it easily outpaces tree growth and through the combination of shading and root competition, it can dominate large areas rapidly. This is particularly true in conifer plantations. I know of entire hillsides that are carpeted with moso bamboo to the exclusion of all but the most hardy shrubs and small trees. In a dense P. edulis grove light is low even on sunny days, and there is essentially only barren ground underneath. Since the root systems are so intricate, the only means of control is by wholesale harvesting of the culms, and this must be repeated over and over until the grove diminishes in strength.

Traditionally, its fibrous culms were fashioned into implements of every imaginable form – from eating utensils, to brooms, poles, water pipes, ladles, umbrellas, and even simple furniture. It was also used in interior wall construction until surprisingly recent times, and even today it is common to see bamboo scaffolding in parts of southern Asia where new buildings are being erected. The simple reason for all this attention is that the culms are harvestable within a very short time compared to true woody trees, making it a readily available, cheap material. Moreover, bamboo fiber in general is amazingly strong, having a tensile strength (measured by the force of pulling on a material) 2/3 that of steel. Its one downfall is that invading fungi and bacteria rapidly weaken the fiber, especially in humid, wet conditions. If kept dry however it remains strong for many years.

In recent times bamboo products, with moso leading the way, have become very popular, in particular bamboo flooring and fencing. Flooring can be stained, lacquered, oiled, or remain unfinished depending on need and desire. It also can be formed into paneling and veneer, and even “carpet” – rolls of bamboo strips than can be laid onto floors. Bamboo fencing and trellises intended for outside use have to be first treated to remove fungi and other organisms, dried, and coated with some preservative if they are to last for more than just a handful of seasons. An interesting factoid is that some of the first incandescent light bulbs were furnished with carbonized bamboo filaments instead of metal ones, a choice that is not intuitively obvious!

In Japan these days moso is mostly commonly used as a spring time food. The large bamboo shoots are collected preferably before they break the soil surface since they are most delicious at that stage. Shoots collected this way in late winter can be eaten raw, as a type of sashimi, and are expensive. More commonly, harvesting takes place when they have just emerged from the ground, but don’t exceed ~30 cm in height, from late April to mid May on Kyushu. The reason for this is that as the shoots elongate, they become tough and bitter, particularly at their base.

As the shoots mature oxalic acid as well as homogentisic acid and its glycosides (notably containing cyanide), making them unpalatable. To remove these unwanted substances, freshly collected shoots must be first cleaned of the outer sheaths and parboiled in water with an alkali agent (rice bran being the most commonly used in Japan). The shoots should be tender before being consumed, a process that takes about 30 minutes for most shoots, but can be longer for larger ones.

Watch this video to see how bamboo shoots are prepared for consumption:

Once boiled they are ready for consumption. Typically they are cooked in a broth of dry flaked bonito fish, salt, soy sauce, and kelp, but recipes can vary widely. They can be eaten as part of a soup, grilled, fried as tempura, cooked with rice, or pickled. The Japanese name for bamboo shoots is takenoko, literally meaning “bamboo child”, and are a favorite spring time food. Since I live in a semi-rural area, many of my neighbors prepare large quantities of these and I never need to collect any of my own since they are always giving me more than I can eat. By early June, to be honest, I don’t want to eat takenoko again for a long time. In midsummer much smaller shoots, usually not more than 5 cm across, are produced, and these too can be eaten, but the harvest is far smaller.

Moso is symbolic of prosperity in Japanese culture, not surprising given its many uses. For this reason it is represented in artwork and religious artifacts. Perhaps the most known of these is kadomatsu (meaning “gate pine”), a New Year’s decoration found at the entrances of homes, businesses, public facilities, and shrines. The basic design is three standing bamboo culms cut off at a diagonal with the openings all facing in the direction it is to be presented. They stand at three heights, the highest one representing heaven, the middle one human kind, and the lowest, the earth. Japanese black pine (Pinus thunbergii) is the other critical component, with boughs fixed to the three bamboo columns. Also commonly, Japanese plum branches (Prunus mume) are placed within the flower arrangement-like structure . The base is often strapped with a straw rope, though variations are many. They can be small, table decorations, but typically stand a meter or more high. They are often displayed in pairs at both sides of an entrance, representing female and male aspects. They are a way of enticing and honoring the ancestral gods of the harvest and remain a common feature in Japan.

Phyllostachys edulis has been known under a variety of Latin names – P. mitis, P. heterocycla v. (f.) pubescens, and P. pubescens. Since the epithet edulis predates all of these it is now the accepted name, and denotes the edibility of this species. The meaning of its Japanese name, mouso chiku, is shrouded in mystery and stories, both varied and contradictory. I’ll spare you the details.

One could go on and on about this remarkable plant. I will always remember it for its beauty. Sitting in a moso grove on a warm spring day listening to its rustling leaves overhead and the clank of culms against one another in the wind is an experience everyone should have. The straight shafts of culms, varying in color from bright blue green (newest), and grading through a rich green (mature ones), and blends of green and orange (more exposed to sun), to nearly pure orange (in full sun) are delightful. Even the spent culms, standing dead and silver gray, often leaning, add to the ambiance. The density of the grove blocks outside sounds to near silence on windless days, and one is transported to a world beyond, a world of serenity and peace. The heart of a mature moso grove is indeed a magical experience.

If one intends to grow this plant, two considerations are paramount. First, do you have enough space to accommodate its rambling habit, and is the local environment likely to support its full growth potential? This is not a plant for small yards and city lots. People may be tempted regardless, using underground barriers as a shield, but this plant is notorious for getting around such barriers. A more sensible means of containing a grove is by root pruning its outer edges every year to a depth of at least 60 cm, but one must be diligent in this task. In humid climates with warm summers and not too cold winters, this species has a high invasive potential. For this reason, groves must be carefully monitored and culled.

Its greatest weakness is the cold. Though it is a temperate bamboo, it cannot withstand temperatures much below -10 to -12 C without being seriously impacted. While it may indeed survive colder conditions, it will not thrive, and the hope of having a grove of giant bamboo will not be realized since culm size and vigor will be negatively impacted. Also, cool maritime climates with mild winters are not well suited to this species either since summers do not get hot enough to maximize this species’ growth potential. Groves of moso do indeed exist in such places as the warmer parts of the UK and coastal Oregon, but are much smaller in stature than what this species is capable of.

So, with those considerations in mind, the ideal place to grow moso is in a warm temperate climate with hot summers, and mild, yet cool to cold winters. Much of the southeastern USA is ideal for growing this plant provided it is planted in moist soils. While it can probably withstand USDA cold hardiness zones 6b-10a, it is optimized for zones 8a-9b, yet still growing well in much of zone 7. Those living in colder winter areas are discouraged from trying this plant for the aforementioned reasons.

It is not finicky about soil, so long as it is moist year round. Deep loams are best, but clays and sandy soils high in organic content are suitable as well. It can endure lots of moisture, but truly boggy sites should be avoided. This is a plant that requires full sun to do its best. Starting a grove takes time, even under the best of circumstances. If you can get starter plants at least a couple meters tall, you may have a mature starter grove within a decade under ideal conditions. You can fertilize during the growing cycle to maximize growth, however in time you may find yourself wondering how to slow your grove down! Plants can also be obtained from growing seeds, but let’s hope you are young enough to enjoy the results – don’t expect to have a mature grove for 20 or more years.

This is a fascinating plant in all respects – a giant timber bamboo, a tasty delicacy, a national symbol, and a source of many useful products. Moso, love it or hate it, is a plant not to be easily overlooked. If you ever get the chance, go visit its groves in Japan or China, and be ready to stand back in awe.