Plant Encyclopedia

The forked ferns of Fukuoka, Dicranopteris linearis and Gleichenia japonica


The forked ferns, family Gleicheniaceae, are some of the more striking looking.  Their forked habit of branching sets them aside as something truly unique.  On Kyushu, southern Japan, two species are common, Dicranopteris linearis and Gleichenia japonica, where they inhabit lower elevations on slopes either in woodlands or on exposed sites.  Let’s have a closer look at these odd ferns.

Gleichenia japonica is an evergreen vining fern with long trailing rhizomes.  Crosiers can originate from the rhizome or from the fork of the branched fronds (pseudodichotomous branching). The new fronds are brilliant lime green and mature to a light green or to dark green depending on exposure to the sun. Each branch is 20-70 cm long and forms a distinct forked frond.  Total frond length can be 1 m.  The stipe is relatively short, 15-30 cm long, and the thicken base is covered in dark brown scales.

 

Gleichenia japonica habitat

Gleichenia japonica often grows in large rambling colonies on moist hillsides.

 

As new crosiers are formed, the resulting vine-like chain of fronds can extend for several meters and form dense colonies.  The frond is twice pinnate, but the pinnules are unlobed.  The undersides of the fronds are a white-blue color (hence the Japanese name, urajiro, meaning “below white”).  Spore production is rare. The circular and naked sori grow in pairs on either side of the costa.

 

Gleichenia japonica crosier

Crosiers of Gleichenia japonica form at the point of the fork in the frond. This bud-like crosier can wait for several months before expanding.

Forming large, dense colonies on hillsides, this species can often be seen growing alongside its near relative Dicranopteris linearis, but often is found on moister sites in heavier shade.  It also is a much larger fern.  Colonies  can adorn whole hillsides, creating a startling visual impact, albeit a bit rambling and “messy” looking.

In Japan this species is famous for being part of New Year’s decorations.  The long connected stipes are also used in weaving traditional baskets.  It is a common fern of well drained, yet moist hillsides in both sun and shade, often seen in tree plantations, along roadsides, and bright woods.  Generally found at lower elevations but found also in mid elevation forests, from 0-700 meters.

 

 

Dicranopteris linearis habitat

Dicranopteris linearis can form extensive, dense colonies, and is always found on slopes usually below 400 meters on Kyushu.

Dicranopteris linearis is a smaller relative, in fact its Japanese name is koshida, which translates as “small fern”, possibly referring to it being smaller than G. japonica, yet similar in habit.  Like its larger relative, crosiers can originate from the rhizome or from the fork of the branched fronds.  The new fronds are brilliant lime green and mature to a nice deep green.  Each branch of the forked frond is 5-20 cm long and a group of six or more forms what looks like a palmate frond or even a whorl.  These whorls can be 35 cm across.

As new crosiers are formed, the resulting vine-like chain of fronds can extend for 3 or more meters.  The stipe can be very short or quite long and is completely smooth, anywhere from 5-40 cm long.  The undersides of the fronds are a white-blue color with a few red-brown hairs.

This species forms small to large colonies on low hillsides, sometimes creating dense colonies that can cover large areas.  An interesting feature is the paucity of spores produced, at least in my observations. I’ve checked entire hillsides and found few if any sori, making me wonder how this species reproduces.  Although it is a colony forming plant, it doesn’t appear terribly invasive.  Raw cuts on hillsides, either by landslide or by human disturbance, are quickly colonized by this and other ferns.

 

Occasionally I’ll see large areas where it has died back, making me further wonder if these areas were in fact just one plant. This plant could be easily mistaken for Gleichenia if not for the fact that it is both smaller and more importantly is only once pinnate while former is twice pinnate (see the photo for comparison).   Hillside colonies are actually quite attractive since they form a nice lush ground cover.

When I first saw these, they reminded me of pictures of Hawaii.  I later found out that this species is actually quite common there!  This is a fern of well drained slopes especially in openings in forests where it often receives quite a bit of sunshine.  It also is common on road cuts, in plantation forests, and in bright shade of loose tree canopies.  It is found mostly at low elevations, from 0-300 meters.

 

Dicranopteris linearis frond

A new frond of Dicranopteris linearis showing its forked habit.

Given their rambling habit one would think these ferns would be a poor choice for the garden, yet in my experience they are modest growers.  In fact, both appear to be quite sensitive to being moved.  For example, some years ago I pulled a loose clump of rhizomes of D. linearis from a roadside hill that was erroding away. It was planted into a mix of kanuma and peatmoss and there it sat doing almost nothing for the next couple years. It was planted out and after two years it finally started filling out, even venturing off into new areas.  I’m experimenting with seedlings now to see if they do any better.

 

Gleichenia japonica sori

Sori are arranged in pairs along each side of the costa - the midrib of the pinnae. This is the same pattern for both species.

While these quickly colonize raw dirt of recent road cuts or landslides, they are much less aggressive in the garden and from what I can see are easily restrained.   Of course, G. japonica, being much larger will require more elbow room.  In the garden, expect D. linearis to grow no more than 50 cm tall and G. japonica up to a meter high.

Unfortunately, these subtropical evergreen ferns shouldn’t prove too cold hardy however, probably only surviving to the very warmest parts of USDA  cold hardiness zone 7 where the soil never freezes significantly. Locally, plants see temperatures routinely in the freezing range, but anything below – 5 C (24 F) will probably cause damage.  Still, they would make a dynamite tropical looking ground cover, especially on a hillside, as an underplanting of palms or tree ferns.

Odd and beautiful, both are worth a try if you’ve got the space and live in a relatively warm climate.

 

Gleichenia and Dicranopteris frond comparison

Side by side one can easily see the difference between these species. Gleichenia japonica is on the left and Dicranopteris linearis on the right.

 

10 Responses to “The forked ferns of Fukuoka, Dicranopteris linearis and Gleichenia japonica”

  1. Berndt says:

    Hello Botany Boy,

    if You have opportunities to collect spores of Gleichenia japonica and Dicranopteris linearis, please let me know. Thank You.
    Greetings from Germany,

    Berndt

    • tommy says:

      Hey Berndt,

      I’ve found that both Gleichenia and Dicranopteris spore in the fall, but being subtropical to tropical species, they could bear spore any time of the year. Having said that, winters here are significant such that new fronds do not start growing until late March when temperatures begin to recover. It isn’t until sometime in fall that new fronds will have ripe spore.

      Interestingly, both species are not often seen with spore, especially the Dicranopteris. I don’t know the reason for this. Both seem to be long lived plants and form extensive colonies that are no doubt many decades, perhaps even centuries, old.

  2. Berndt says:

    Hello Tommy,

    interesting, what You write. May be Dicranopteris is at the borderline of its distribution that it refuse to produce spores??
    Please let me know if You have chances to collect spores of Gleichenia japonica in autumn 2012. That would be a very interesting species to nurse. Please leave the messages on andwari@live.de
    Thank You very much. Kind regards
    Berndt

  3. tommy says:

    Hey Berndt,

    Locally neither species is at its geographical limit since both are found well up the coastlines of Honshu. Also, recent road cuts with raw earth are favorite “spore grounds” for ferns in general, and sporling plants of both species frequent such places.

    As far as finding spore of them, I’ve done impromptu surveys of local colonies and have found that less than 5% of mature fronds bear any spore at all. With the Gleichenia I occasionally find a frond or two sporing freely, but so far with the Dicranopteris I’ve just seen a few sori here and there.

    Both are common hillside plants in the Fukuoka area at lower elevations. I grow D. linearis in my garden, so perhaps it will be more likely to produce spore than wild plants. I’ll keep you informed.

    Tom

  4. Berndt says:

    Hello Tom,

    that would be very, very nice, to get some spores. Gleichenia would be more amazing for me, because I have some sporelings of Dicranopteris here (hopely it is Dicranopteris; At this moment they look like any fern :-) )

    Do You also have Diplopterygium in Japan?? I know it only from Hawaii and China. Also a very interesting specie and worthy to nurse, I think.

    Unfortunatly Europe has a big lack of any Gleicheniaceae and relations. We know them as fossils in many forms – mostly from the mesozoican coastlines, when middle europe was built of many islands.

    Berndt

  5. tommy says:

    Hey Berndt,

    To my knowledge the only members of the forked ferns in Japan are the the two above mentioned species plus Gleichenia laevissima, a rare fern in Japan and confined to Kyushu and the southern islands. Diplopterygium pinnatum looks almost identical to G. japonica – at least from the photos I’ve seen. Other members of the genus I am completely unfamiliar with.

    One plant I love in this family is Gleichenia truncata – what a wonderful fern! Ditto with G. hirta. Unfortunately, they are truly tropical things, so there is no hope of growing them in climates that experience any frost.

  6. Berndt says:

    Hello Tommy,

    indeed, I agree with You regarding the beauty of Gleicheniaceae. Here in Europe there is no recent species, but many fossils. I do not know the reasons for extinction. I try to rise a Dicranopteris-species. They are now 1 1/4 years old – and yes, they grow slowly. They like thin amounts of fertilizer but seem to look not very “gleichenia-like” in the youth but like any other fern. The frons are thin and spliced, resemble som Hymenophyllums or Davallia. So at the moment I am not sure if they are really Dicranopteris…:-)
    Would be great, if You have chances to collect spores from Gleichenia japonica – a beautiful species.

    Ben

  7. Mutlu says:

    Hi, interesting stuff. I tried Australian Gleichenia and Sticherus from spore without sucess. do you have a succesfully procedure to raise gleicheniceae from spore? Is any special method?

    • tommy says:

      Honestly I don’t know of anyone who has even attempted to grow these genera from spore. Both Dicranopteris linearis and Gleichenia japonica are rapid colonizers of raw earth – usually from landslides or new road construction – so I can’t imagine they would need anything special. In my experience poor germination is due to old spore, or spore that wasn’t collected at the correct time. As a rule, freshly collected spore that hasn’t been in stored in a refrigerator is best, but also the toughest to source.

      It is interesting to note both species in this article spore very infrequently in the wild here, especially D. linearis. I had no idea why.

    • Ben says:

      Hello Mutlu,

      I have tried some Gleicheniaceae from spores (Dicranopteris lineata, Diplopterygium sp., some others from Chile and NZ). Dicranopteris was most successful. Young Gleicheniaceae looks very different from the “adult” ones, more like Trichomanes or Davallia, very thin, fine feathered leaves.
      I took sterilised lime-free substrate (Bonsai-mixture)and small acryl boxes. It seems like with all (?) ferns that spores should be fresh to germinate. Germination can take 2 years. Young plants need high air moisture and with some fertilizer then they grow rapidly. Recording light: they must take what they get here in northern Germany in a normal appartment :-) Good luck. I Would like to get informations if You stark cultures.
      Ben

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