Osmunda japonica - Japanese Royal Fern

Osmunda japonica, also known as Japanese Royal Fern or Japanese Royal Osmunda, is a Japanese species, closely related to the Royal Osmunda, but still not widely distributed in Europe. It resembles its giant cousin of flooded areas, but differs by having a more limited growth and its ability to produce two types of fronds in spring with striking dimorphism; entirely sterile fronds, of a bright green colour, mixed with exclusively fertile fronds evoking powdered cinnamon branches or browned coral branches. Its vegetation is more enduring in autumn, and it is less demanding in water, content with a moist, non-limestone soil. Over time, this venerable fern forms a "trunk" at the base, and can live for more than a century.

Osmunda japonica is a terrestrial fern belonging to the family of Osmundaceae, just like the Royal Osmunda that haunts the edges of our ponds and marshes. But this original species is native to the East of Asia, from the Russian Far East to the mountains of the Himalayas, Taiwan, China, and Korea. It is particularly widespread in Japan where its highly appreciated young shoots are consumed as vegetables. While it is very popular and almost invasive in the Land of the Rising Sun, this fern remains a rare plant for us Western gardeners, and very difficult to find in commerce.

Osmunda japonica is a calcifuge perennial plant (that does not like limestone), with long deciduous petioled leaves, arranged in a cluster, not exceeding 70 to 80cm (28 to 32in) in height. The plant renews itself every year from a thick rhizome that sometimes forms a caudex (swollen stem serving as a storage organ), and produces a stipe (a kind of thick stump resembling a trunk, formed by the overlapping of foliar sheaths) whose length reaches about one third of the length of the frond. Often solitary, this species is capable of forming large colonies if the conditions are right.

In spring, woolly and brittle croziers emerge, of beige colour, which simultaneously unfurl two very different types of fronds. The sterile fronds, 60 to 80cm (24 to 32in) tall, are wide and erect, pinnate, strongly divided into green leaflets. Among them emerge the fertile fronds, about 50cm (20in) tall, therefore shorter and highly specialized. They appear in the form of branched candelabra-like structures, covered with a thick powdery layer made up of thousands of naked spores. When ripe, these curious 'inflorescences' take on a characteristic cinnamon colour, which earned the royal ferns the name of Flowering Ferns. The Japanese Royal Fern retains its green foliage longer than the Royal Osmunda, until late in the season. Then it takes on a beautiful reddish colour before disappearing.

You can plant the Japanese Royal Fern in moist undergrowth, or on the edge of ponds, streams, and wet rockeries, preferably close to a rocky area by the water where it will become a queen, or in shaded areas in large masses.

We grow all species near our stream, in the marshy soil of the banks where they reach their full value. Its mere presence gives a fantastic character to the most ordinary stream. Avoid mixing it with other ferns, but rather associate the Osmunda japonica with woodland flowers with which it will not compete, such as hellebores or hostas. The light blooms of Masterworts or Astilbes are very beautiful among ferns. They make great companions for small bulbs such as wood anemones, Naples cyclamens, or lily of the valley. The decorative and colorful foliage of Heucheras and Saxifrages is remarkable. Some Japanese maples (Acer palmatum) with laciniate and finely toothed foliage also appreciate the cool and sheltered sun environments, and in autumn, they blend their beautiful colours with the reddish foliage of this Osmunda.

The genus name of this fern, Osmunda, has many origins attributed to it. This name was given by Mathias de l'Obel. It may come from Osmund, a Germanic deity equivalent to Thor in Scandinavian mythology. Or, it may come from the Latin os, meaning "mouth," and mundo, meaning "purify, clean," in relation to the antiputrid properties of certain ferns. Osmund is also originally a Saxon name meaning the peace of the hearth: from mund, meaning "peace," and os, meaning "house."