Yukiwariso: Small Jewels from Japan

An exhibition plant of Hepatica nobilis var. japonica ‘Benisudare’, displayed against a porcelain plate  hand-painted with images of Japanese hepaticas. Author’s photographs

An exhibition plant of Hepatica nobilis var. japonica ‘Benisudare’, displayed against a porcelain plate hand-painted with images of Japanese hepaticas. Author’s photographs

They are small, beautiful, and expensive. They have a cultish following among Japanese, American, and European plant lovers. Their blossoms are only an inch in diameter; yet, when touched by light and the warmth of early spring, a whole world opens up in each one. Meet the famed Yukiwariso, “the flower that breaks through the snow,” a symbol of the arriving spring in its mountainous habitat of Japan.

Japan is heaven for anyone who loves plants .and gardens. The traditional garden aesthetic .and its ancient methods are deeply rooted in society and visible everywhere. Countless publications for Western audiences have addressed the Japanese aesthetic in gardens, flower arranging, and bonsai. Yet, little attention has been given to the fact that most Japanese have only a tiny amount of space to explore their gardening passions. As a people, they have an understandable desire to add life and color to their homes and a special craving for things small, unusual, and precious. Many Japanese nurseries and garden centers cater to these needs and desires by offering a range of small and delicate ornamental plants. Japanese growers have a long history of selecting and breeding exceptional cultivars of such plants and give decided preference to their native flora.

Members of the many specialized plant groups and societies eagerly cultivate, propagate, and display their favorite ornamentals with considerable dedication. Their taste for adventure often leads to the successful cultivation of plants that were previously considered too difficult to survive outside their natural habitats.

The Western plant lover may not have heard much about the inexpensive and beautiful Manchurian violet cultivars—nor of some extremely expensive and unusual variations and mutated forms of otherwise ordinary and well-known species. But for the last ten years, the rumor of an extraordinarily stunning plant—called Yukiwariso in its homeland—has spread among American and European plant lovers.

Yukiwariso is a species of liverleaf or Japanese hepatica (Hepatica nobilis var. japonica), a perennial herb that grows no taller than a few inches. Japanese hepaticas belong to the buttercup family (Ranunculaceae), whose prominent members include Aquilegia, Clematis, and Helleborus. Its closest relations are in the genus Anemone, from which, by botanical-systematic standards, it differs only slightly. Yukiwariso belongs to one of two sections within the genus Hepatica. Cousins of Yukiwariso grow in Europe (Hepatica nobilis subsp. nobilis and H. transsilvanica) and North America (H. acutiloba and H. americana), but show far less variation in flower color and shape.

The simplest flower shape of Hepatica nobilis var. japonica is one called Hyoujunka

The simplest flower shape of Hepatica nobilis var. japonica is one called Hyoujunka

A National Passion

For more than twenty years, these precious plants have been commanding much public interest in Japan. Each year hepatica exhibitions take place in Tokyo and Niigata, a city in the plant’s native region (the northwestern coast of the main island of Honshu). The Japanese Hepatica Society organizes these exhibitions and, for a fee, also registers new cultivars. (There was also a short-lived American Hepatica Society active during the 1990s.)

Yukiwariso were also favorites in past centuries, when blossoms were displayed floating on the surface of shallow, water-filled ceramic bowls. Paintings from the nineteenth century show the plants with flowers of different shapes and colors. None of these earlier examples survive in cultivation. Around the late 1800s, when Japan opened up to international trade and industrialization of the country was beginning, the hepatica sank into oblivion and remained there for many decades.

Only in the 1970s did this Japanese hepatica reemerge. An expedition of plant enthusiasts in the mountains surrounding the city of Niigata discovered hepatica blossoms in the most unusual shapes and colors. The discovery set off a craze comparable to the 1980’s art boom in New York City or the Tulipomania in Holland centuries earlier. Within the next few years, several hundred unique clones of Yukiwariso had been selected and named.

Most Japanese hepaticas have single flowers of white or pink; finding more unusual ones involves a lot of searching. (The “petals” are actually petaloid sepals; typical of many genera in the family, true petals are non-existent.) Unfortunately, the arbitrary collection of plants has seriously depleted their total numbers in the wild.

Variations on a Theme

The blossoms can display a wide range of colors: green, white, pale yellow, different tints of pink, tomato red, and variations of magenta, purple, and violet. There are also light blues, middle blues, and blues as dark as the skies of a clear night. The petal of the single flower can display various patterns: edged, spotted, freckled, or attractively veined. The petal’s shape can be twisted, the edge can be rolled towards the inside, or the tip can have an indent or two. Nine flower shapes are recognized by the Japanese Hepatica Society. The finest of each shape entered in the two annual shows is awarded a prize.

The flower shapes of Hepatica nobilis var. japonica,  from the top: Otome-Zaki

The flower shapes of Hepatica nobilis var. japonica; Otome-Zaki

Hyoujunka is the term given by collectors of Japanese hepatica for a single blossom with normally developed stamens and pistils. Otome-Zaki is the term for a single flower with intact pistils, but without stamens.

Nichirin-Zaki

Nichirin-Zaki

The stamens of Nichirin-Zaki appear as short, infertile, (usually) green petaloids that evenly surround the normally developed gynoecium (the cluster of pistils). The highly priced and sought after Nidan-Zaki has a wreath of straight, flat, nicely colored petaloids of equal or different length surrounding the normally developed gynoecium. Similar to Nidan-Zaki, Chyouji-Zaki has colored petaloids that do not lie flat but twist and turn irregularly. Karako-Zaki has the features of Nidan- or Chyouji-Zaki, but with layers of petaloids completely covering the gynoecium. Karako-Zaki are much less common than the two preceding shapes.

Karako-Zaki (‘Kuukai’)

Karako-Zaki (‘Kuukai’)

Sandan-Zaki (‘Asahi’)

Sandan-Zaki (‘Asahi’)

When a flower of the Sandan-Zaki shape is fully developed, the stamens and pistils are infertile, (usually) green or greenish petaloids. However, younger, poorly cultivated, or recently divided plants might produce a fertile anther; these can be used to pollinate other plants, thus increasing the number of seedlings with unusual flower shapes. To some, Sandan-Zaki may be of questionable beauty, but they have, along with some spectacular Nidan-Zaki and Senju-Zaki, the highest price tags. Rare and exceptionally attractive cultivars of these three shapes sometimes are sold at prices approaching $5,000 per rosette!

Senju-Zaki (‘Sannohzakura’),

Senju-Zaki (‘Sannohzakura’)

Most cultivars of Senju-Zaki are exquisite doubles introduced from the wild. They are called the “thousand-layered” flower, and many of them are extremely expensive. Some of the most famous are native to Senka Island, which lies off the coast of Niigata.

Yousei-Zaki (‘Kaguyahime’)

Yousei-Zaki (‘Kaguyahime’)

The shape of a Yousei-Zaki flower is the result of careful breeding programs. It fits between Sandan- and Senju-Zaki, but also shows a similarity to Nidan-Zaki. Recently introduced as a competition class, it has a layered wreath of straight petaloid stamens. Some of the pistils may be intact, but the majority are developed into petaloids, though usually less showy than the ones on a beautiful Sandan-Zaki cultivar.

The leaves, produced in a loose basal rosette, also betray great diversity and beauty. The plants maintain their foliage for the whole year, and each cultivar’s leaves have a unique pattern and shape. Lovers of marbled and silver-leafed plants have reason to be delighted. There are also cultivars with variegations in other colors and with irregularly shaped leaves.

Availability and Breeding

Due to popular demand, budget-priced garden centers in Japan offer seedlings from crosses of valuable parent plants, implying to the unknowing customer that something of outstanding beauty might emerge. It usually doesn’t. More often, the result is a plant with no special features, though still attractive.

Dedicated growers must rely on a few specialty nurseries. There, they can find a huge selection of unnamed plants and older seedlings, as well as a range of named cultivars and choice F1-hybrids. As there are so few nurseries capable of meeting specialist needs, many purchases are conducted via mail order, while some Japanese collectors travel long distances to choose a favorite plant during flowering time in March and early April. In the past few years, Yukiwariso have also been available throughout Europe and North America (see the Resource Guide, page 21).

Many of the long-standing named clones, most of which were originally collected in the wild, have been continually propagated through division, consequently becoming more available and affordable. However, plants multiplied through micro-propagation, the only other means of clonal reproduction, did not flower true to name; therefore, the existing trial clones are considered to be inferior. Technology failed here. A good specialist nursery would not offer any of these plants for sale.

To reproduce plants of the simplest flower shape (Hyoujunka) with specific color features, self-pollination achieves good results. Selecting the finest of the offspring may produce plants of even better quality. The breeding of all the other floral shapes involves luck and requires a lot of space. Thousands of seedlings have to be brought to bloom; in the end, only a few possess unusual and desirable characteristics.

Nidan-Zaki

Nidan-Zaki

The breeding of the fully double Senju-Zaki provides an example of the breeder’s art. The pollen from a rare fertile anther on a Sandan-Zaki must be used to pollinate the pistils of a Nidan-Zaki. The method is still only occasionally successful, yet it produces more Senju-Zaki plants than might be likely to appear as sports (mutations arising on a mature plant). Only two Japanese nurseries are involved in large-scale breeding. Each spring, other nurserymen, seeking material for their own businesses, descend upon them to select promising seedlings during their first flowering.

It takes about three years for the hepatica seedlings to flower, and, even then, the blossom does not yet show its full potential. With good care and another two years, the seedlings will flower at their finest. It is at this point that plants considered worthy are named and registered. The length of time, the unusual effort, and the expense incurred in the cultivation of hepatica must be considered when looking at the prices, which are, by Western standards, indeed outrageous. The enthusiast must pay between $50 and $300 for a fine, named cultivar—and does so without hesitation.

Yukiwariso differ from the easily reproducible, mass-marketable plants sold in Western garden centers. They are plants for life. Once acquired, the care invested will assure greater rewards from year to year. A single rosette will develop into a substantial cluster in a few seasons; meanwhile, the blossoms become larger and more beautiful with each passing year. If the plants are neglected, they withdraw but do not resign quickly. If care is improved, they will always offer a second chance.

The instructions that follow are based on the cultivation methods practiced by professional Japanese growers. The plants are grown in pots, where they easily develop to their fullest and most beautiful, as pot cultures are easier to control. Nevertheless, Yukiwariso will happily grow outside; the care requirements are the same. Japanese hepaticas are hardy in USDA zones 5 to 8; on the West Coast, they are best adapted to cultivation in the Pacific Northwest.

Chouji-Zaki

Chouji-Zaki

The Natural Habitat and the Consequences for Home Cultivation

All species of Hepatica are ground-dwelling plants of deciduous forests in the Northern Hemisphere. They have similar demands, and vary mostly in their degree of hardiness, which depends on the conditions of their natural habitat—low plains, hills, or mountainous areas up to 3,500 meters (11,500 feet).

Japanese hepaticas are found throughout the mountain ranges of the country’s islands, most abundantly in the northern part of the main island of Honshu. During winter, the plants are usually covered by fallen leaves and a substantial layer of snow, both of which protect the plants against strong freezes. When the snow melts in March, the flower buds push through the receding snow and open, warmed by sunlight reaching the forest floor through the leafless canopy.

Shortly after flowering, the new leaves start to grow. During this phase, hepaticas receive plenty of moisture. From the end of May, the actual precipitation diminishes slightly due to the increasing canopy leaf coverage. From then on, the forest trees soak up the greater part of the available sunlight and moisture. For this reason, hepaticas are accustomed to the dry spells that regularly occur on the forest floor; to successfully cultivate liverworts, it is important to wait for the soil to dry between waterings during the summer months.

The beautiful leaves rarely fall victim to pests, but they are vulnerable to other hazards. Too much sunlight or contact with chemical fertilizer burns the leaves. Protection against over-watering is essential. The number of leaves that develop each year depends upon the quality of care given the plants in the previous year. Any leaf lost will not re-grow and will weaken the plant.

Some European collectors call hepaticas the “slow-moving mistress.” Indeed, it takes time for the plants to gain (or regain) size. By the end of summer, plants will have matured and will usually have developed one or more additional growth buds, called ”eyes.”

From September on, the moisture level on the forest floor increases significantly and a second period of root growth takes place. Soon the plants will be buried under a cover of fallen leaves and, later, snow. Protection from ground frost is a vital part of the care of hepaticas in the harsher climates of North America and continental Europe.

The Japanese Approach to Cultivation

Plants ordered by mail from specialist growers arrive, unless otherwise specified, with only one eye, some leaves, and several roots. (For clusters of two or more eyes, the price usually multiplies accordingly.) If they are not already potted, the roots are wrapped in moist sphagnum moss. In this case, the best time to order is August or September, providing the plants with enough time to settle into their new surroundings before winter arrives. From October on, they should be protected from excessive warmth and sunlight, which could force the plants to flower prematurely.

In Japan, hepatica growers use deep pots made of dark, burnt clay. The bottom of the pot consists only of wire mesh for the free drainage that is essential. They are placed on benches, on shady porches, or in airy conservatories, where the small plants can be conveniently enjoyed at close range.

As a component of the planting medium, growers use unburnt, coarse clay pellets. These pellets, called Kanuma, Rinuma, and Akadama, are not available in Western garden centers, though a good bonsai nursery may be able to supply them (or a reasonable substitute). In any case, a pH-neutral, free-draining mix of both organic and mineral content should be used. Starting in spring, an organic fertilizer should be given on a regular basis; a mild, long-term organic fertilizer is the best choice. (A Danish hepatica grower covers his plants with cow dung each spring, and the results are reported to be amazing.)

When flowering is past, the flower stalks and old leaves should be cut off. The newly developing leaves must not be disturbed, as they are important for the quality and number of flowers and leaves in the next season. During summer, the plants should only be watered when the medium’s surface feels dry, whereas, in spring and fall, steady levels of moisture are most appreciated.

Propagation

The only way to propagate hepatica cultivars is through division. The best time for this is late summer, after the plants have matured. Division should not be undertaken until the plant has reached a size where it has about five to seven eyes. Division is vital for potted plants, which deteriorate if they become too large; division of plants in the ground is less critical as they usually increase in beauty
with size.

Wash the soil off the roots and carefully separate the eyes. Each division needs several healthy roots and a few leaves. Large plants with substantial rhizomes can also be propagated from root cuttings. New divisions must always be replanted in fresh soil.

Propagation from seeds is easy, but requires a lot of patience. Flowers are typically hand-pollinated; seeds should be harvested in summer and sown while still fresh and green. It can take up to two years for seeds to germinate, and another three or four years to flowering size.

Pests and Other Problems

Japanese hepaticas are not prone to pest infestation; snails and slugs usually find tastier treats. Mites or nematodes, residing in the roots, can harm the plants, though not fatally. When the plants are divided, the knots formed around these pests should be plucked away and the roots treated with a systemic control against such pests before they are replanted.

A common complaint lodged by buyers of Yukiwariso concerns the quality of the flowers. Both older plants kept in unsuitable conditions and freshly divided plants do not always develop flowers in their full beauty. Plants of Chyonji-Zaki may have missing or underdeveloped petaloids, and those of Sandan-Zaki may not develop the green petaloids in the center. These problems should disappear with good cultivation.

Not only the rare and extravagant cultivars, but all Japanese hepaticas, when grown well, are gorgeous. As small, beautiful, and superfluous as a Franklin Mint collector’s piece (but of unquestionably better taste), they are perfect items for the plant connoisseur; the enormous variety in floral shape and color provides endless shelf-filling options.