Author: Tom

Japan is home to a number of Polystichum species, but two dominate in southern Japan’s forests, P. polyblepharum and P. tripteron.  The former is common at low elevations here in Fukuoka, belying its preference for the warmer parts of Asia, while the latter is a straggler to Japan’s southern forests, more suited to the cold temperate woodlands of northern Asia.

Polystichum polyblepharum is an evergreen fern with a short creeping rhizome that sometimes forms a small trunk. The frond is twice pinnate, growing up to 100 cm long.  They grow in a rosette forming a near perfect circle.  The pinnules are boot shaped and have slightly toothed margins with a pointed tip.  The round sori are in rows along the costa.  The thick, fleshy stipe is covered in large cinnamon brown scales and accounts for about one quarter the length of the frond. The unfurling croziers hang down at their tips, giving them a drooping, tassel-like shape typical of this genus. While this fern can create offsets from the rhizome, the plant is more commonly seen growing as a  single rosette of fronds.

In Japan it is widespread from Honshu and southward.  It is also found in South Korea, and the warmer parts of China.  In the Fukuoka area it is found in moist woodlands from near sea-level to over a 1000 meters. This is one of the most commonly seen woodland ferns in Fukuoka and indeed much of the warmer parts of Japan.  One of its most distinguishing characteristics are the large cinnamon colored scales that cover the stipe and rachis.  They are particularly noticeable when the croziers just emerge.

The half grown fronds hang down as they elongate, giving this fern its English common name, the tassel fern.  The overall visual impression of this species is very pleasant since it forms perfectly circular rosettes of fronds up to 2 meters across in vigorous specimens, but more commonly half that size.

The upper surface of the pinnae are a beautiful,  glossy green that gives off a bluish sheen.  A multitude of white hairy scales cover the lower pinnae surfaces and give the plant its Latin name, polyblepharum, meaning “many eyelashes”, however they are not easily seen by the naked eye.

In truth there are a number of near look alike species from this genus, and to tell them apart you have to closely examine their scales and pinnae.  If that weren’t bad enough, members of this genus hybridize readily, thus compounding identification.  I have decided to avoid all that and simply lump them all under this species.  A lazy approach, but one has to be careful how time is spent in life!
Continue reading “Two Japanese tassel ferns, Polystichum polyblepharum and P. tripteron”

An unusual and attractive plant that doesn’t quite look like a fern is Sphenomeris chinensis.  While few westerners have even heard of this fern, it is in fact a common plant in much of east Asia and Polynesia.  Its 3-pinnate fronds and tiny wedge shaped pinnules give it a uniquely delicate look and has earned it the common name lace fern.

S. chinensis is a fairly small evergreen fern with a short creeping rhizome.  Fronds are produced throughout the warm months and are 3 times pinnate giving them a very fine textured look. Frond length is variable depending on the exposure to the sun with long fronds growing in shadier locations.  They can be anywhere from 10-100 cm long and 8-20 cm wide, but typically don’t grow more than 50 cm long.   Although the pinnae grow in an alternating pattern, there often exists a basal pair of pinnae that are separate from the next pair further up the rachis by several centimeters.

These basal pinnae are the largest on the frond and the rest get progressively smaller as they approach the tip of the blade giving the frond a long triangular shape.  The tiny pinnules are wedge shaped with the wide end at their terminus.  At the end of the pinnules the small oval sori are born singly or in pairs. The reddish-brown stipe is completely scaleless and hairless, and accounts for nearly half of the frond length on large fronds.  These ferns are commonly seen growing in loose colonies on nearly vertical slopes.

S. chinensis is found in the warmer areas of Japan including Honshu (Niigata, Yamagata, and Fukushima Prefectures and southward), Shikoku, Kyushu, the southern islands to Okinawa, as well as Korea, Taiwan, China, Indochina, the Philippines, Papua New Guinea, India, Nepal, and the South Pacific Islands (Hawaii, Cook Islands, Tonga, Marquesas Islands, and Samoa).  It perhaps has been reported from Madagascar, but this may be a mistaken record.  It is listed as a potential exotic weed in New Zealand.

This lovely little fern can be seen in any moist forest in moderate to light shade, however it  is also found on sunny roadsides in thick growth of grasses, herbs, and small shrubs.  It seems to like to colonize raw earth in cuts created by roads, paths, and landslides, and also on natural rock outcrops where moisture is abundant.  Seen from near sea-level to 1000+ m, but most common in low to mid elevations, 50-600 m, on Kyushu.

At first glance with its 3-pinnate fronds it can seem to be a Selaginella, but a closer look shows that it is indeed a type of fern.  The frond’s shape is unusual, especially with its numerous, tiny wedge shaped pinnules.  The overall appearance of the fronds is very soft and pleasing.  It is mostly found in bright locations, from sunny roadsides to bright woods along stream banks, and is a common species in the Fukuoka area.  In the fall and winter the fronds can get purplish if in an exposed position, thus adding to its charm.

Happily, it is easy to grow.  I’ve had one in the garden for several years now and have given it no attention except to make sure that surrounding plants don’t out-compete it.  In fact the only problem I’ve had is that it grows too well, so it is necessary to prune back larger fronds from time to time.  This is a fern that requires bright light to grow well, and also needs a well drained, yet continuously moist soil.  In nature you never see it in a flat place, so drainage is sharp.  It is not fussy, so any reasonable woods loam is fine for this one.  One drawback is its lack of cold tolerance, perhaps only hardy to USDA cold hardiness zones 7-10.  It is a lovely compact growing fern if grown in bright light, but more airy and large in darker conditions.

Its Japanese name is horashinobu, meaning “cave Davallia” from the words hora (“cave”) and shinobu, the name for the epiphytic fern Davallia mariesii, which it not only resembles, but is related to.  Another typically obscure Japanese name!  The genus name, Sphenomeris, is from the Greek words spheno meaning a wedge and meris meaning a part, probably referring to the wedge shaped pinnules.

I have only praise for this lovely fern.  If you can get one, do so.  They are lovely to look at, easy to accommodate, and compact in size – in short, a must have plant for the serious fern collector or warm climate gardener.

 

An edible fern that is well known to all Japanese people is Osmunda japonica, called zenmai in the Japanese language.  This widespread fern is in fact not only delicious, but a lovely plant in and of itself.

Osmunda japonica is a large deciduous fern with a thick rhizome that occasionally can form a small trunk (caudex).  There are two frond types that show extreme dimorphism:  the spore bearing sporophylls and sterile trophophylls.  The sporophylls emerge concurrently with the trophophylls and grow vertically to a height of 30-70cm tall.  Approximately half way up these specialized fronds opposite pairs of branches form (analogous to the pinnae) and off these are paired spore bearing structures – highly modified pinnules.  These are literally covered in cinnamon brown, naked spores, hence giving many in the genus the name cinnamon fern.

The trophophyll by comparison looks much like a typical fern frond and is twice pinnate growing anywhere from 60-100cm long and 40-60cm wide.  The pinnae grow in opposite pairs off the rachis and the oblong pinnules occur alternately and usually are unlobed.  The stipe accounts for a third of the length of the frond.  The impressive crosiers emerge covered in whitish-brown hairs, but these soon fall off leaving the stipe and rachis completely smooth.  Plants usually occur as a single growth with no offsets, but often forming extensive colonies.

This species is widespread on the mainland islands of Japan, also Russia (Sakhalin), Korea, Taiwan, China, Indochina, and the Himalayan Mountains.  It is common in moist to wet forests, field-like slopes that are annually cut, seepage slopes, road cuts, swales, and ditches.  On Kyushu it can be found at all elevations, 0-1000+ meters.

O. japonica is one of the better known ferns in Japan due to the emerging crosiers that are collected each spring as a seasonal food.  Traditional foods in Japan are deeply linked to the seasons, no matter what type; roots, herbs, shoots, and even fish.

In spring it is common to see cars parked along roadsides, and people out foraging for their favorite herbs.  Zenmai is often eaten with takenoko (bamboo shoots) taken from the huge bamboo species called moso, Phyllostachys pubescens.  Each spring my neighbors come to my door with both takenoko and zenmai as a seasonal gift.  These are prepared by boiling them in a pot with water and some seasoning such as shouyu (soy sauce), su (vinegar), and sato (sugar) until soft.  As my girlfriend says, “it is a taste of spring!”  Another commonly eaten fern in spring is warabi, Pteridium aquilinum, a species that is a known carcinogen.  I’ve heard that zenmai is not as dangerous, but being on the safe side, I only consume either in any quantity in the spring, and just a couple of times a year.

The fern itself is very common, being found just about anywhere there is adequate moisture.  It is very reminiscent of its relative O. regalis, but is more stout in stature.  The conspicuous spore bearing fronds emerge alongside the sterile fronds in mid spring and are quite lovely in and of themselves, and thus earning this type of fern the nickname “flowering ferns”.  In fall their foliage turns a bright yellow and is attractive for a short time.  It can occur as a single clump or form extensive colonies, but always in the company of other fern species.

I’ve grown this one for many seasons now.  It appears to be pretty easy in a lightly shaded to partially sunny location with evenly moist soil.  Any good loam will do for these just fine.  They are not wetland dependent like O. regalis.  Given their wide natural distribution, I’d say they can be grown over a broad range of climates (USDA cold hardiness zones 3-10).

The Japanese name, zenmai, means a “spring, coil, or mainspring” and probably is a reference to the shape of the crosier which looks like a coiled spring.  This word is used in Japan to mean the crosier as a food eaten in spring or the fern as a species.

I think this cinnamon fern is a lovely addition to any suitable garden.  While it is similar to the more commonly known O. regalis, it is no less lovely, and possibly easier to grow as well.   The hardest part will be finding plants for sale on the international market.

 

Japan is home two miniature spleenwort ferns, Asplenium trichomanes and Asplenium incisum.  Both frequent rocky outcrops, with the former preferring moist sites in the shade while the latter is found in brighter places that are on average much drier.

Asplenium trichomanes is a tiny semi-evergreen fern.  Throughout the growing season it throws its tiny fronds in a small, loose rosette.  Each frond is once pinnate and between 5-10 cm long.  The pinnae are slightly lobed, roughly oval in shape, and grow in an alternating pattern down the black, wire-like rachis and average no more than 0.5-1 cm long each.  They are a dark blue-green color.  The oval sori grow in pairs on opposite sides of the costa.  The black stipe is quite short.  Both the stipe and rachis are scaleless.  It commonly forms large colonies even coating rock faces, but also can be seen in small groups.

This  is a truly worldwide fern being found on every continent except Antarctica and even on some Pacific Ocean islands including Hawaii, and is represented by a number of subspecies throughout its impressive range.  In Japan it is widespread from north to south.  Some subspecies are polyploid (having more chromosomes than the normal compliment), but the Japanese plants are not.  This is a fern that grows on rocks or in the cracks of them exclusively.  On Kyushu it seems to prefer wet rock faces that are also subject to seasonal drying.  It grows from bright to dark shade.

Here is a remarkable little fern.  It can be found scattered around almost every temperate climate across the globe as well as some subtropical areas, and even odd places such as the mountains of Yemen and east Africa. In Japan it likes to grow in the company of its own kind and also alongside many other lithophytes including various types of fern, selaginellas, mosses, lichens, and so on.

Despite its delicate appearance, it can withstand drying even to the point of seeming death.  It can be found hanging completely desiccated in loose groups of crumpled fronds, however, like many lithophytic and epiphytic ferns, come the next rain its foliage re-hydrates and looks as good as new.  Another desirable feature it has is its truly miniature stature.  This is one tiny fern, usually not exceeding the breath of a human hand.  This one may not be a rarity, but it is a delightful little denizen of Japan’s rocky forests.

The Japanese name for it, chasenshida, is rather whimsical, meaning “tea whisk fern” from the words chasen (“tea whisk”) and shida (“fern”).  The overall shape of the fern uprooted looks much like a bamboo whisk used to make macha tea.

A. incisum is very similar in size and form to A. trichomanes.  Obvious differences are that the pinnae are strongly lobed, the rachis is green, and the pinnae are a light green color.  Each pinna is much more elongated than in A. trichomanes and the variation in size, shape, and spacing along the frond’s length is more pronounced, with the middle blade pinnae being the longest and largest.  While the sori grow in an alternating pattern on opposite sides of the costa, they are elongated as well.  It is most commonly seen singly or in small groups, but occasionally occurring in larger colonies.
Continue reading “Two miniature spleenwort ferns from Japan, the maidenhair spleenwort and the tiger tail fern”

Japan is home to one of them more interesting woodland ferns – the so called “upside down fern”, Arachniodes standishii.  This medium sized fern is neither common nor rare in my neck of the woods, but is always a welcome sight, especially in June when the newly grown fronds grace the banks of streams and coves of cedar trees.

A. standishii is fairly large evergreen fern with fronds that can exceed 60 cm, but usually are no more than 50 cm.  The broad blades are 15-20 cm across.  The fronds are three times pinnate and a pleasant rich green color.  The stipe is relatively short (no more than 20% of the total frond length), and has brown scales at its base.  The pinnules of are more heavily veined on top then on their lower surface and they hang down giving the frond an upside down appearance (hence one of its English names, the upside down fern).

The sori are kidney shaped and mature spore a rich red-brown color.  The rhizome is short, creeping, and occasionally branching.  This species can form dense colonies, but commonly occurs in association with other types of fern in sporadic clumps.

Being found throughout Japan’s main islands and South Korea, this species seems indifferent to temperature.  It favors moist to wet woods, often along streams, and especially conifer plantations where it can form extensive colonies.  This fern seems happiest on wetter sites in light to deep shade at mid to moderately high elevations (~300 to 800 m) in Kyushu.

Continue reading “Another Japanese woodland fern, the “upside down fern””

Seldom heard of outside their native range, the Plagiogyria species of warm temperate Japan are common evergreen ferns of wet, humid forests.  Their Japanese name is kijinooshida meaning “pheasant tail fern” since their broad, once pinnate fronds vaguely resemble the tails of those fowl that frequent the same woodlands.  They are in fact delightful to the eye, yet elusive since they seem rather difficult in cultivation.

Plagiogyria japonica is a common, small evergreen fern with two distinct frond types: fertile (sporophyll) and sterile (trophophyll).  The sterile fronds are more showy with broader pinnae, and are 8-30 cm long and 3-8 cm wide.  The pinnae are simple, flat, and oblong.  They extend nearly from the base of each stipe to the very tip of frond in opposing rows presented in a flat plain, and are longer at the center of the frond with each one 1-4 cm long and 5-8 mm wide.

The sterile fronds grow in a lovely rosette and usually have an elegant arch to them.  The fertile fronds grow vertically, are much taller, and have much more narrow pinnae.  They stand 15-45 cm high and 3-8 cm wide with each pinnae being 2-4 cm long and 3-5 mm wide.  They too are born in opposite pairs on the stem but are highly reduced towards the stipe, and grow much looser on the stem as well.  The croziers start out bright electric green to deep red and the new fronds often have this same color for some time.  The plant grows from a simple branch less, creeping rhizome.

This fern is found from central Honshu (Kanto region) westward to Yamaguchi Prefecture and throughout Shikoku and Kyushu in any moist forest in deep to light shade, but is most frequent and vigorous near streams and seeps.  It also seems to like rock walls and rock cuts provided there is ample water.  Found from sea level to ~1000m.

These are very attractive ferns, very reminiscent of a Blechnum which I mistook them for at first.  Like members of Blechnum, the dimorphism between fertile and sterile fronds is great.  The fertile fronds are amazing to watch as they unfurl:  they start all coiled up and slowly unfurl into exquisite lime green, wire-like structures.  They are a sight to behold on a fine spring day with the sun back lighting them.  Many months later, in late fall, they are heavy with brown spore.  This fern is widespread through the mountains here.  In all respects it is a most lovely small fern.
Continue reading “Two evergreen ferns of Japan; the pheasant tail ferns, genus Plagiogyria”