Southern Japan is home to three common species of brake fern in the genus Pteris: P. cretica, P. multifida, and P. nipponica. Pteris cretica is perhaps the best known of these, also called ribbon fern in the horticultural trade, and can be seen in almost any nursery or big box store selling tropical foliage plants. It isn’t a truly tropical species in Japan however, and neither are its two companions. They are in fact at home in the rocky woods of Japan’s warm temperate forests – warm being relative since winters here can get rather cold, and even snowy at times.
All three are a common sight in my area, just on the outskirts of Fukuoka City, on the island of Kyushu. By far the most often seen is P. multifida since it is a veritable weed in these parts, growing out of just about any crack in a wall – natural rock or concrete. It is also the smallest in stature of the three. The other two are closely related, to the point that one needs to look at them carefully to see the differences. Never are any of them very far from rocks, or seeps of water, and yet they are neither bog plants, nor true lithophytes. I’ll tackle them one by one, starting with the weedy species, P. multifida.
P. multifida is an evergreen, clumping fern commonly seen growing in cracks in rocks, rock walls, and also disturbed soil. Its fronds are of two types, spore bearing and sterile. Their overall shape is similar except that the spore bearing fronds are perhaps twice the size of the sterile ones and all parts are much more narrow and elongated. This fern is once pinnate, with pairs of simple pinnae extending off the main stem, or rachis. The pairs of pinnae usually number between 4 or 5 per frond with the base pair being the shortest, and subsequent pairs being longer, and again becoming shorter toward the end. The terminal pinna is typically very long and singular – a trait common to many Pteris species. Each pinna is rarely more than one cm wide. The base of the stem (also known as the stipe) as well as the rachis are smooth, scale-less, and brown in color.
An interesting feature of this species is a wing-like structure growing along the length of the rachis between the pairs of pinnae. Close examination shows these wings to in fact be extensions of the uppermost pinnae growing clear down the rachis to the next pair and terminating there. The pinnae are presented in a flat plane in some individuals while they can be very wavy in others. The margins of the pinnae are roughly toothed, but not lobed. Sterile fronds grow between 12-30 cm in length, while fertile ones can be half again that length. Typically these are small ferns though, with a total height of not more than 20 cm on average. The fertile fronds tend to grow more vertically, while the sterile ones essentially hang parallel to the ground. Both frond types usually are a pale green color and slightly shiny.
Both Pteris cretica and P. nipponica have a similar overall habit to P. multifida, with the big differences being their larger size, wider pinnae (2 to 3 cm on average), and a lack of wings along the rachis. Typically these ferns have sterile fronds 30-40 cm in length and fertile ones up to 60 cm or more. Vigorous specimens can be even larger. As with P. multifida, their sterile fronds are more gracile in habit, yet with all parts more elongate, and growing more erect.
Spores are born on the outermost margins of the fertile fronds. They are actually naked, that is they have no covering (a membrane called the indusium) during their development. In place of indusia are the pinnae margins themselves, which literally roll over the spore as they develop and later open up to release the mature spores – this type of arrangement is called “false indusia” – another trait common to all Pteris species.
So, how to tell them apart? In general P. cretica has pinnae presented nearly flat, the pinnae margins are just lightly toothed, the fronds are not shiny, and the overall frond color is a light green to almost lemony green in newer fronds. P. nipponica on the other hand usually has pinnae with very wavy margins, the pinnae margins are also more strongly toothed, the fronds are shiny, and the frond color tends to be a darker, almost blue green. I’ve noticed also that P. nipponica fronds tend to show a lightening in color on all pinnae along the main vein, so much so that in some specimens they are bordering on being mildly variegated.
Still, it is often difficult to tell them apart in the field. The true separation can be made by looking at the terminal pinnae pair and the terminal pinna itself. In P. cretica all three pinnae almost fuse at their attachment to the rachis, while in P. nipponica there always is bare rachis between the three. Additionally, the terminal pair of pinnae in P. cretica have an almost wing-like extension, reminiscent of P. multifida, but much less developed. Taking all these features into account, one can separate these species in the field.
All three of these brake ferns can be found from north central Honshu and southwards to Okinawa. Of the three, P. multifida is the most common and grows well into the Touhoku region of northern Honshu. P. cretica makes it almost that far north, but is more rare in central Honshu, becoming common southward. P. nipponica is even more rare in the north, barely straying north of the Kanto area (near Tokyo), and yet is frequently seen in Shikoku and Kyushu.
Outside of Japan, P. multifida is widely distributed in southeast Asia clear to Indochina. P. cretica too is widely distributed and has become an escape over much of the subtropics and tropics the world over. P. nipponica is more restricted, being found in the southernmost reaches of the Korean Peninsula, and Taiwan. P. multifida as well has become naturalized outside its range, for instance, the southeastern USA and even on Long Island, New York.
All three ferns seem to like vertical habitats, either on actual rock walls, or on steep slopes. With that generalization in mind, P. multifida tends to grow on drier sites, often in cracks in rock walls, cement structures, and relatively dry rocky slopes. It is a common weed of the city, coming up as volunteers in yards, or on rough rock walls, etc. P. cretica seems the most water loving from my observations, being often found growing on the verge of trickling seeps on rocky hillsides, or near water courses. P. nipponica likes a similar moist habitat, but usually is found near or on rock walls (in cracks) or on moist rocky slopes, but not in wet places.
A little bit about their common names. P. nipponica does not have a name in English, but P. cretica has been commonly known as “ribbon fern” due, no doubt, to the ruffled, ribbon-like quality of its pinnae. P. multifida is sometimes called “spider brake” or “spider fern”, due to its thin pinnae spanning out in all directions from its crown, presumably looking like a big spider. The word brake is from Middle English and appears to be related to the word bracken, both words simply meaning “fern”.
Their Japanese names are perhaps more interesting. P. mulifida is called inomotosou, roughly translated as “the herb that grows under the well”, since in the days when rock water wells were more common, you’d often see this plant growing where the water dripped below the spout. The name for P. cretica is oobainomotosou, simply meaning “big leafed herb that grows under the well” due to its similar appearance to P. multifida while being a larger plant. P. nipponica has an enigmatic name, matsuzakashida, which is obscure in meaning. Matsuzaka is a fairly common surname in Japan, who’s Kanji characters roughly translate to “pine slope” or “pine hillside”, however the Kanji for this fern’s name have apparently been lost to time. Shida simply means “fern”.
To see these species in the field, and how to differentiate them, check out this video. In it you will also see the three other common Pteris species in the Fukuoka area: P. dispar, P. excelsa, and P. wallichiana:
P. cretica and P. multifida have both become locally exotic weeds. In Florida I remember seeing Pteris cretica growing in old lime rock quarries. Apparently it is also common in Mexico and Guatemala, but more rare, yet widespread, in the rest of Latin America. Its Latin epithet, cretica, means “of Crete”, so it is sometimes called the Cretan brake fern, which is odd indeed. The truth is, no one is sure of this plant’s original distribution, though I tend to think it is from east Asia. P. cretica is of importance horticulturally with many varieties that have been isolated and mass propagated. The more commonly seen ones include ‘albolineata’ (a variegated form also known as “silver ribbon fern”), ‘mayii’ (variegated with crested pinnae), and ‘rowerii’ (another crested form). There are many more. Variegated forms of P. nipponica can even be seen in the wild, though I haven’t been fortunate enough to find one yet. From pictures I’ve seen, they are even nicer than variegated forms of P. cretica.
In terms of cultivation, you commonly hear these are ferns that like limey soils and that all are quite frost sensitive. I’ve found just the opposite here in Japan. While it is true you see P. multifida growing on concrete walls, in the wild it is found in acidic humus in and amongst rocks. The same is true of the other two species. They are found quite far north in Japan, especially P. multifida, which also ranges well into USDA cold hardiness zone 7 in New York. I’d guess that P. cretica and P. nipponica should be hardy to at least zone 8, perhaps even zone 7 for the former species.
A few cultural hints. Give them lots of water, however maintain good drainage. They will respond well to a variety of soils, from near neutral to acidic, and with varying amounts of organic material. Personally, I would grow them in an even mix of humus to perlite or the like. They definitely require humid conditions to do well. P. multifida is capable of handling full sun, while the other two are decidedly woodland plants. I would guess all would make excellent terrarium subjects. Like virtually any fern, they require humid conditions to flourish, so may prove difficult as house plants, particularly in centrally heated homes.
One word of caution, something that can be said of almost any Pteris fern – they tend to become pests when happy. P. cretica is found throughout the warmer parts of the world today, a testament to its propensity to spread. I’ve found P. multifida to be an absolute nuisance in the garden since it is constantly sporing in from the surrounding neighborhood. Pteris species produce a lot of spore and it germinates readily. Even the relatively sought after large species, Pteris wallichiana, spreads rapidly when happy. So, please be mindful, especially if you live in a warm, moist climate. These plants can become exotic pests.
In all likelihood few of you will ever grow these species as they exist in the wild, but just as likely some of you already have grown one of the cultivars of P. cretica. I find them to be fascinating plants, and some of the variegated types are quite gorgeous, but I suspect I will always enjoy them out in the field rather than in my garden.