Japan’s largest hardwood, the camphor tree, Cinnamomum camphora

Native to the wet forests of subtropical and tropical Asia, the camphor tree, Cinnamomum camphora, has been planted across the world’s warm temperate, subtropical, and tropical regions.  It is a tree of many faces – a stately forest giant in its native range, a rampant pest in eastern Australia, a source of spice in south Asian cuisine, a shade tree in Florida, a natural pesticide – the list goes on.  Its defining feature is the essential oil that can be extracted from its tissues and the cocktail of aromatic chemicals that give the oil its pungent, fresh odor.  Of these, camphor is the star – a highly aromatic terpene like chemical.

Cinnamomum camphora is a massive broad leaved evergreen tree that grows to 30 m tall (some sources report even higher) with a broad sweeping crown.  The spread of the tree can equal its height in field grown specimens, truly a breath-taking thing to see.  The trunk can grow to over two meters in diameter with the top end reported to be 8 meters. The largest I’ve seen was around 3 meters.

The leaves are dark to light green and glossy with lighter colored veins, 8-15 cm long and 3-7 cm wide.  Leaf shape is highly variable, sometimes ovate and some elongate, each growing in alternating positions on twigs.  The bark is rough and brownish-grey.  The tiny star shaped flowers are in lose clusters in mid spring and are white.  By November the dark blue berries ripen and are quite small, less than 1 cm across.  The new foliage in spring flushes purple-red, then turns brilliant electric green, and finally maturing rich green.  During new growth and just after (April and May) the previous year’s leaves fall, and are a lovely orange-red.

Camphor trees are found throughout the warmer regions of Japan as far north on Honshu in the Kanto region, Shikoku, Kyushu, and the islands southward to Okinawa.  Beyond Japan’s borders it is found in much of east Asia including China, Taiwan, Korea, Indochina, and India.  In Japan it grows in warm temperate and subtropical forests on mountains and further north in coastal forests.  It grows to 800 meters elevation in the south, then found at progressively lower elevations northward, and finally restricted to coastal low forest in central Honshu.  It can be dominant in some forests, but most often is mixed in with other broad leaved trees.

This is another member of the Laurel Family (Lauraceae), hence its other name, camphor laurel tree.  In the broad leaf evergreen forests of southern Japan this species sticks out due to its incredible size and mass.  It once was used in the production of camphor oil, especially before WWII.  It has been grown as a specimen tree in the warmer parts of the world, and in certain regions it has become an invasive pest.  In Japan it is well behaved, forming a lovely spreading tree in time.

In an old growth forest on one of the local mountains, huge specimens occur, commonly have trunks more than a meter across.  Truly massive trees aren’t necessarily that old, perhaps just a hundred years in some cases.  A few temple specimens are thought to be around a 1000 years, but ages are often exaggerated.  Today old growth forests containing these trees are a rarity, existing in small patches.  This is another iconic Japanese tree, widely grown and beloved, thus it has a strong future in this country.

 

Camphor tree uses are extensive, and although its essential oil was more commonly used in the past, even today it is used in perfumes, insecticides, explosives, deodorants, in Japanese foods (beverages and sweets), in south Asian cuisine, and medicines.  Crushed leaves give off a potent camphor smell.  Although this oil is potentially toxic, it still can be found in many over the counter creams, lotions, and antiseptics.  Camphor wood is used to make furniture, in general carpentry, and as veneers and inlays.  It is a favored wood in Asia due to its natural ability to repel insects, and for its lovely grain and color.

The historic medicinal uses of camphor include as anti-inflammatories, antiseptics, antimicrobials, anesthetics, anti-flatulents, stimulants, and pain relievers. It is still commonly used in over the counter cooling and anti-itch gels in combination with menthol.  Though these topical applications are yet permitted in the U.S., oral medicines were banned in the 80’s, and the FDA has restricted total camphor content  to 11%.  Current medical opinion is that camphor is useful in relieving coughs when applied as a chest rub, for treating itching and irritation of the skin (bruises, minor burns, insect bites, etc.), and as pain killer when used as a rub on lotion.  There is some evidence of temporary relief of stiff joints from osteoarthritis, again when applied topically as a lotion.  There is not enough evidence to support its use in treating toe nail fungus, hemorrhoids, warts, or any other physical ailment.

Camphor oil itself a more complex cocktail of chemicals, including camphor, borneol, 1,8-cineole, linalool, nerolidol, and safrole.  This last one in particular, safrole, is a known mild carcinogen found also in sassafras, nutmeg, black pepper, and basil.  In the U.S. safrole was used as flavor but now is banned by the FDA for that purpose.  Much has been written about the different forms of camphor tree based on the proportions of these chemicals, so called chemotypes.  Some chemotypes have been considered highly toxic and much literature has been generated about the danger of these trees, though the bulk of that seems to be anecdotal.  Sound scientific, peer-reviewed studies are few and inconclusive.  In the end, camphor oil probably isn’t that bad, but daily use (particularly orally) is likely to cause problems, and in extreme cases, even death.

In the 1800’s camphor trees were planted across the globe in regions as far reaching as the southeastern USA, Hawaii, and Australia.  They were brought in originally as ornamental shade trees and also as a source of camphor oil in Australia, but its commercial viability never was realized.  In Australia camphor laurels (as they are called there) have become an invasive pest, and today the planting and distribution of this tree is illegal in the states of New South Wales and Queensland.  Here they have taken over waterways, dropping large amounts of their pungent leaves into them.   Camphor trees also have invaded old pastureland, and are replacing native eucalypt forests.  In the southeast USA, particularly in north and central Florida, the tree has become an invasive weed, especially on roadsides, fallow pastures, and disturbed sites.  Within the state it is listed as an exotic pest, but is not on state or federal noxious weed lists, so its movement within the USA is not restricted.  In Hawaii it is common in some areas, and given the delicate island ecology there it could become yet another exotic threat to those island’s native plants and animals.

The Latin name, Cinnamomum, is from the Greek word “kinnamomon”, meaning cinnamon since this genus is known for aromatic barks that can be used as a spice, especially C. zeylanicum, the source of cinnamon “sticks”.  In the past, C. japonicum was used in Japan as a form of cinnamon as well.  The species epithet, camphora, refers to camphor, the famous chemical constituent in the oil found in the tree’s tissues.  The Japanese name is kusunoki, derived from a single kanji character, and simply meaning “camphor tree”.

This is probably the most commonly grown laurel tree in the world.  It has been cultivated just about anywhere it can withstand the winters.  It seems fully hardy to USDA zone 8b, although cold winter snaps can damage it severely.  During the winter of 1985 temperatures in Gainesville, Florida dropped to a record breaking -12 C. I remember two old camphor trees living on the main route through town suffered great damage that year, losing 50% of their crowns. Damage to the smaller branches probably occurs when temperatures drop below -7 C or so.  It is rarely grown in yards in Japan due to its huge size, but is frequently seen in parks, on broad avenues, and most especially at temples and shrines.

Check out this video of huge camphor trees in their native home on the flanks of Tachibanayama, a mountain on the fringes of Fukuoka City, Kyushu, Japan:

It isn’t a demanding tree, although it needs a well draining soil, sun, and not too severe winters.  It has been reported to be drought tolerant, which is interesting since in its native range it grows in humid, wet climates.  Furthermore, it seems happy in soils ranging from acidic to basic (pH 4-8).  Although it is a lovely tree, I would be remiss not to mention the potential invasiveness of this species in warm, wet climates.  In Australia it is invasive in the wet northern areas.  Likewise, in America it is invasive in the southeastern hardwood forests (in particular Florida), yet is a slow growing and well behaved tree in the warmer areas of the Pacific Northwest, being grown even in south coastal British Columbia.  The plant spreads rapidly due to its prodigious seed production with a single mature tree bearing 100,000 or more per season.  Birds readily eat these, spreading them far and wide.  The upshot is that outside its native range, it needs to be handled with care.  If you live in a cool and/or dry climate it may be reasonable to grow this one.  On the other hand, if your climate is warm and wet, it is probably irresponsible to grow it.

Love it or hate it, the camphor tree is embedded within human culture for the duration.  It too has extended its range over much of the world’s wet tropical and subtropical regions.  Given its ability to reproduce, it will likely remain naturalized in those areas regardless of efforts to eradicate it.