A shield fern of southern Japan, Ctenitis maximowicziana

The warm temperate forests of southern Japan are home to a shield fern who’s most notable feature are the scales that cover its long stipes. This fern is so scaly in fact that they have earned it one of its Japanese names, the grey haired fern. The newly emerging croziers come up like a ball covered in so many of them that indeed it does look like the head of an odd white haired creature.

Ctenitis maximowicziana crozier
The emerging crozier of Ctenitis maximowicziana looks like some odd white haired creature on the forest floor.

Ctenitis maximowicziana is a medium sized to large evergreen fern growing from a short, creeping rhizome. The fronds are few (usually five or less) and ascend in a graceful arc. They are a light green color and three times pinnate. Each is from 50-100 cm long and 30-50 cm wide. The stipe accounts for one quarter of the length of the frond and is covered in large white and brown scales. These continue up the rachis nearly to the frond’s end, and also extend out onto the pinnae. The sori are round and are in pairs around the vein (called the costule) of each pinnule. Plants occur in small groups or singly.

This fern is found in the warmer regions of Japan from Honshu (most commonly in the Kanto region and westward, but with a northern outpost in Akita Prefecture), Shikoku, Kyushu, and the islands south of Kyushu including Okinawa. It is also reported from Taiwan and China. It seems to prefer moist ravines near water, but not at the water’s edge. This lovely woodland fern is found in both natural forests and in conifer plantations from 300-500 meters elevation on Kyushu.

Without a doubt, the most outstanding feature of this shield fern are its scales. From the time the croziers emerge in spring and throughout the frond’s life, the numerous lovely white and brown scales of the stipe and rachis are undeniably attractive. In spring the emerging crozier is brilliant lime green and literally covered with these, creating a unforgettable image. The scales brown with age and look best in the spring. Though not uncommon in Fukuoka, this fern is not frequently seen either, occurring in scattered areas. Without a doubt, this is one of Fukuoka’s most beautiful ferns.

Ctenitis maximowicziana in habitat
The fronds of Ctenitis maximowicziana hang in a graceful arc. The stipe and rachis are completely covered in white and brown scales that have earned it one of its names in Japan, the grey haired fern.
Ctenitis maximowicziana stipe
The scales up close.

The genus name Ctenitis means “comb” from the Greek word kteis. The species epithet, maximowicziana, is in honor of Carl Johann Maximowicz (1827-1891), a Russian botanist and curator of the Saint Petersburg Botanical Gardens. This fern is in the shield fern family, Dryopteridaceae, and is placed in the genus Dryopsis by some authorities. In the field it may be confused with another fern, Thelypteris torresiana, but that species lacks the tell tale scales of C. maximowicziana.

The Japanese name, kiyosumihimewarabi, means “noble princess bracken” from the words kiyosumi meaning “pure or noble”, hime meaning “princess”, and warabi the Japanese word for bracken fern. Yet again another obscure name. It also has an alternate name, shiragashida, coming from the word shiraga meaning “white or grey hair” and shida meaning “fern”, a reference to the white and brown scales found on the stipe and rachis. At least that makes sense!

Ctenitis maximowicziana spores
The sori of Ctenitis maximowicziana occur in pairs along the costa of each pinnule.

I’ve never tried this one before, but I suspect it shouldn’t be that challenging in a moist and shady garden. Given its distribution, it should be cold hardy to USDA zone 8-10 (perhaps a bit lower with adequate protection and careful siting).

As with many obscure Asian species, this woodland fern is virtually unknown in cultivation in the West. In truth, it is little known in Japan, except by fern enthusiasts, and is never seen as a garden subject. That is too bad since this graceful fern would be a great addition to warmer woodland gardens the world over.


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