Southern Japan has a peculiar climate that has allowed essentially subtropical forests to exist in what is technically a warm temperate climate with four distinct seasons. This forest is home to many orchids and ferns that one wouldn’t expect to find in a place that happily supports such things as daffodils, cherry trees, and temperate rhododendrons.
Among these are the epiphytic and lithophytic fern species that make their last northern stand on the islands of Kyushu, Shikoku, and the southeastern coast of Honshu. This article is the first of several about these northern stragglers. The following species can all be seen within a short bike ride from my house on the eves of Kyushu’s largest metropolitan area, Fukuoka City, and in fact could even be called epiphytic weeds.
Without a doubt, southern Japan’s most common and widespread epiphytic fern is Lepisorus thunbergianus. It can be found on almost any tree or stone wall whether it’s in the country or city. In truth, some of the most dense colonies I’ve seen are in urban parks and cemeteries. Not surprisingly it is also the most conspicuous epiphytic plant species around. To the untrained eye it might seem to be some strange grass growing up in the trees since it grows in clumps and has long, grass-like fronds. It often is found in association with Fukuoka’s next most common epiphytic fern, Lemmaphyllum microphyllum.
L. thunbergianus is found growing on the boles, branches, and even twigs of trees. It also grows on any available rock surface, concrete wall, or wood structure such as a wooden roof or post. While usually found at lower elevations, it can also grow higher up in mountains, up to 800 meters or more. Truly, this isn’t a picky fern, but it cannot survive on the forest floor. Many thousands of plants fall to the ground, and they all perish with no exceptions. In dry weather the fronds crinkle up and look positively dead, but the next rain they plump up again. This is a species that will never be in short supply in Japan.
A smaller relative to L. thunberianus is the diminutive L. onoei. In the Fukuoka area this species is confined to higher mountain ridgelines, usually above 700 meters elevation. At these altitudes the more common L. thunbergianus is replaced by this more diminutive species where it can form extensive colonies on tree trunks. Other than simply being smaller in stature than L. thunbergianus it also has a rounded frond tip, a diagnostic feature. See the comparison shot of the two species growing side by side to see the difference. As seen in the picture, L. onoei is less than half the size of L. thunbergianus. It is a lovely little plant of cloud shrouded mountain ridgelines, at least in the Fukuoka area.
Next to L. thunbergiana, Lemmaphyllum microphyllum comes in a close second as Fukuoka’s most common epiphytic fern. In truth it is just as happy growing on rocks as it is on trees. In either case it can form impressive colonies, virtually covering the entire bole of a large tree or huge protruding rock outcrop. The tiny round leaves have earned it various names, including the common English name “green penny fern”. In fact the plant has two types of fronds, one fertile (the sporophyll) and the other sterile (the trophophyll). The sterile fronds are nearly round and lay flat to their growing surface and give the plant its characteristic look. The fertile fronds are much more narrow and flare upwards in an arc away from the growing surface.
From a distance the plant can give the impression of a dense mat of rough moss, and closer inspection would not make you think of a fern right off the bat. It is a common plant growing on rocks and trees in mostly shady forests, but can be found on rock walls, concrete walls, natural rock outcroppings, and virtually any tree species, preferring hardwoods with a coarse bark structure. It also grows as a twig epiphyte, often dangling from a branch precariously. Found from low to moderately high elevations, up to 600 meters.
Check out this video showing L. thunbergianus, L. microphyllum, and a number of other epiphytic ferns growing naturally in the Fukuoka area:
All three species are fairly easy to grow. Of the three, L. onoei is the most cold hardy, easily taking down to -10 C (14 F) in its native habitat. The other two can handle -5 C (24 F) no problem. While in growth these ferns like lots of water and humidity, but also require a drying period between wettings. If they stay continuously soggy they will rot and eventually die. L. microphyllum is the most tolerant of continuously wet roots, but it doesn’t appreciate it very much. While they all can handle a humidity range from 30%-100%, above 60% is ideal. None like too much sun exposure, but can handle some. Avoid midday sun however.
All attach well to any wood or tree fern fiber and can also be grown in pure sphagnum in clay pots – avoid plastic since these retain too much moisture. In winter they are happy to handle colder temperatures, but the average should remain above freezing. In summer they thrive on hot, humid conditions, above 25 C (77 F) at all times, though you can most likely grow them cooler. One thing, if you live in a subtropical, humid climate be careful with L. thunbergianus since it truly can be a weed. Same thing in a greenhouse – their spore will germinate everywhere and soon you’ll have too many. I routinely have to weed my epiphytic garden trees of them or they would soon overrun the place! Fun plants that require no fuss, I recommend trying a few.