Japanese laurel, Aucuba japonica

The warmer forests of Japan are home to a large evergreen shrub which is now grown world wide, the so called Japanese laurel, Aucuba japonica.  At first glance this plant reminds one of a rhododendron in growth habit and a holly for its berries, but in fact it is more closely related to the dogwoods.  In Japan it is at home in the wet valleys and ravines of mountain forests.

Aucuba japonica is a large evergreen shrub or small tree standing 2 to 5 meters in height.  It has a ranging habit with branches bending and twisting every which way in the deep shade of its mountain home, in search of light.  The leaves grow opposite each other and seem to dangle off the ends of the long, sparsely branched stems in clusters.  Despite this, the overall look of the plant is full, perhaps due to the large size of the dark green serrated leaves.  Each is 7-25 cm long and 4-10 cm wide.  The serrations are few, but large.

The leaves give off a lustrous sheen that can seem bluish from a distance, giving the plant its Japanese name, aoki, meaning “blue tree”. It is one of the few plants that actually seems to favor conifer plantations, especially in the lower valley slopes near water, and often in deep shade.  Given its ability to live happily in such forests, this species has a secure future in Japan.

The flowers are born in loose clusters, are very small (5-7 mm), and star shaped.  They just precede the new growth, starting in March and continuing through April.  The four (sometimes five) petals are maroon in color with a green center and sometimes are edged in white.  While they are too small to be considered showy, each is very pretty when viewed closely.  This plant is dioecious, that is, there are separate sex plants with male flowers and female flowers.  The oblong fruits that grow only on the female plants start out bright green and turn deep orange-red in winter.  Wildlife seems to disdain these, so they last well into spring before falling to the ground.

Aucuba japonica is found in the warmer regions of Japan as far north on Honshu as Miyagi and Yamagata Prefectures, and southward to Shikoku, Kyushu, and the southern islands.  It also grows in South Korea, Taiwan, and southeast China.  It is found in warm temperate to subtropical moist forests on mountains as an under story tree or shrub.  In Japan it commonly grows in hinoki (Chamaecyparis) and sugi (Cryptomeria) plantation forests as well. It is usually found at lower elevations, less than 500 meters, particularly along streams and wet seepy slopes.  Plants can occur singly in a woodland, but are most commonly seen in large, dense groups.

Though often called Japanese laurel, it is in fact a member of the family Garryaceae, cousins to the better known dogwood family (Cornaceae) of which it was included until recently.  This is one of the more common small Japanese tree species in the low elevation forests of the south, particularly along streams, on seepage slopes, and in plantation forests.  It seems to occupy the same niche as Rhododendron maximum does in the southeast USA, growing in tangled, dense colonies not unlike the “laurel slicks” or “hells” of the southern Appalachian mountains.

A good hiking buddy of mine who thru-walked the Appalachian Trail with me in 1996, commented about about this plant one day, “hey, look at those rhododendrons!  I didn’t know they grew in Japan too.”  At a quick glance they do seem very similar.  Closer inspection will reveal big differences however –  serrated leaf margins, clusters of small purple flowers in spring, and never mind the bright red-orange berries the female plants sport in winter.

The Japanese name, aoki, means “blue (green) tree”…hmmm…this is one of those funny moments when you ask, “what do words really mean?”.  Ao definitely means “blue”, but apparently can also mean “green” in Japanese.  Presumably it is called this due to its evergreen habit, or perhaps due to the bluish sheen from the leaves.   The scientific name,  Aucuba, is in fact a Latinization of the the Japanese word set ao-ki-ba, meaning “blue-tree-leaf”, though it is never called by those words in Japan.  Many folks mistakenly call it Acuba, missing the first “u”.

This is a very attractive plant despite is ranging habit.  A variety of cultivars have been created, most notably variegated leaf forms, the most common being the Aucuba Gold Dust variety, sometimes called v. variegata.  This plant is commonly used in Japan as a sheared shrub or hedge, but only the variegated types.  Not surprisingly, pruning aucuba is simple – just shear it like you would an azalea, or if you don’t like the chopped leaf look, then hand prune the smaller branches.  In the sun it grows much more full, so pruning is easy – ones in the shade tend to be rather rangy in habit.

It appears indifferent to soil reaction or composition as long as it stays moist, a key point as this is not a plant that likes dry roots.  It is said that the leaves are sensitive to sunburn, though I have not witnessed this in my area and plants are commonly grown in full sun here.  Perhaps in a drier climate this is a problem – keeping the roots moist should prevent any problems.  It is a better looking shrub in some shade however, and is capable of growing even in very deep shade.  Happily, this plant has not been shown to be an invasive pest in its adopted countries – an important consideration when choosing exotic plants for the garden.  Though it is fairly cold hardy, at least to USDA zone 7, protection from winter winds in exposed spots is recommend due to the large leaf surfaces.

Another important issue is to make sure you know the sex of the plants you’re buying since only the females fruit.  In a similar vein, you need a male plant to insure a good set of berries.  If you can buy plants during flowering (early spring) take a good look at tiny flowers.  The males will have four small yellow stamens arranged in a circle around the flower’s center, while the females will have one central green pistil.  A single male plant is enough to pollinate several females nearby, so you don’t have to get more than one to do the job.  The berries are a lovely feature of growing these since they are not eaten immediately by wildlife, giving months of viewing pleasure.

Propagation is straight forward – either by seed or cuttings.  Of course when growing by seed it is not known beforehand if a male or female will result, so plants should be grown to flowering size before siting them in the garden.  In wild plants, especially in very wet areas, short aerial roots grow on the old wood along the stem nodes.  These can be made into fast establishing cuttings by either clipping and planting the stem or by air layering.

Japanese laurel was a plant destined for horticultural use based on its lovely features, as well as its ease of maintenance and propagation.  While it is an overlooked shrubby tree of Japan’s wet woods, it also is the star of many a garden worldwide.