Japanese Irises

Unlike any other iris variety, the Japanese irises have attained a cult status, especially in Japan. Initially it was an ordinary iris species with a preference for water; the Japanese iris has been bred extensively during the last 500 years with a view to develop flowers that are spectacular, as in the instance of Higo iris. The main objective of breeding the plants was to obtain an iris variety that is excellent for indoor display. Similar to the well known tea ceremony as well as the specialized flower arranging schools, people in Japan usually bring home a potted Japanese iris just ready to bloom in a heavily ritualized manner and adhering to strict rules. In order to highlight the exquisiteness of the normally white or vivid single hued flower, the pot is placed before a golden screen so that people can watch it opening over the next three days. This is continued through quiet mediation while the flower opens gradually to display it utmost beauty. Several years back, an iris species called I. ensata was found growing extensively throughout Japan realizing a more fundamental purpose. In the era when calendars were yet to be introduced, farmers in Japan depended on the seasonal changes for guidance regarding the time when they should plant and harvest their rice crops. For instance, they started cultivating their fields when the cherry trees were in bloom. Similarly, they were sure about the arrival of the rainy season when the irises were in bloom. It also signified that the time was appropriate for transplanting the rice plants from the seedbeds/ nurseries to the paddy fields. The grace and style of these ordinary flowers inspired the Japanese hybridizers, who undertook experiments with natural iris selections and cross-pollination way back in the 17th century. Over the next two centuries they developed new iris cultivars that were superior to the original species. By the 19th century, they had started exporting these cultivars to the United States. In addition, several public gardens came up and prospered in the vicinity of Tokyo. Earlier, people grew irises in paddy fields. With the new public gardens, people residing in the city visited these places with a view to get some respite from their busy lives. Over the years, the hybridizers successfully developed three distinct strains of Japanese iris. Each of these strains possessed individual traits and gradually became familiar among the people. On the other hand, the strains that were developed in paddy fields over several centuries were christened Edo - the primeval name for Tokyo. These strains produced a variety of blooms that differed in color, size as well as form. Japanese breeders developed an iris strain called Ise strain with the main objective of growing it in containers. This strain received its name from the place of its origin, located roughly 50 miles from Kyoto in southwest direction. The blooms of this iris variety have a propensity to have a single form, whose falls are in a hanging or pendent position. Irises developed in Higo, an old Kyushu province, have been developed from those of the Edo varieties. These irises were also developed with the aim of growing them in containers - grown outdoors when the weather conditions are suitable, but taken indoors when they are about to bloom. For these iris breeders, the most important aspect was the flawlessness of the blooms. With the Higo strain becoming available freely and exported to the Western countries, the people's interest in breeding these plants bearing wonderful flowers increased. They now focused on breeding plants for growing outdoors. However, it is really unfortunate that many of these cultivars were lost due to the World War II. In fact, succeeding breeders in Japan as well as the United States have developed crosses between these three iris strains. As the characteristics are fading now, it is fitting to call all these cultivars by a common name - Japanese irises.


Ideally, Japanese irises should be planted to a depth of approximately 3 inches in a fertile soil containing substantial organic substances. Japanese irises should be planted or transplanted during the fall, as this is the best time of the year for undertaking such activities. While plants of this iris variety require lots of water during their growing season, you need to be careful that you do not plant them beside any water body like ponds or streams. Subject to the vitality as well as the growth of a particular plant, Japanese irises will develop congested clumps in just three or some more years. While the crown of the plants will be drawing close to the surface of the soil, the stems will become small and there will be sparse blooms. When this happens, it is actually an indication that the time is right for lifting the plants, dividing the clumps and transplanting them. You may also undertake the division and transplantation of these plants soon after their flowering season or during fall, when there is new root growth. Japanese irises generally thrive well in acidic soils and hence. Ideally, the pH of the soil in your garden should be 5.5. As a limy soil or lime are detrimental for the growth and survival of these plants, never grow Japanese irises close to any place where mortar work like laying new foundations, concrete walls or erecting mortared walls has been undertaken recently. At the same time, never feed Japanese irises with bone meal, as it discharges lime into the soil. Moreover, the bone meal available these days is not of much use, as most of its nutrient value has already been extracted. Therefore, it is always better to use super phosphate in its place. If you wish to increase the acidity of the soil in your garden, you may add agricultural sulfur as well as lots of humus or even compost in a proportion of about 1 pound to 3 pounds per 100 square feet. Blend these substances to a depth of roughly 10 inches to 12 inches and subsequently allow them two to three weeks time or even more to settle down. The time that you need to give these substances to settle depends on the prevailing weather conditions. Undertake a test to find out the soil pH and repeat adding agricultural sulfur if you find that the pH is elevated. In fact, reducing the soil pH is relatively difficult compared to increasing it. In fact, sulfur lowers the pH at a faster rate when the weather is warm and in some specific soils. Adding chelated iron products to the soil also helps to raise the acidity of soil, especially when you work such products into the soil. Usually, fertilizers meant for rhododendrons and azaleas contain chelated iron products. In fact, Japanese irises provide an indication when the soil becomes too basic or alkaline. In such circumstances, the foliage of the plant will turn yellow (chlorotic), while the leaf veins will continue to remain green. If you find that your favourites irises are suffering from this condition, you should know that you need to lower the pH of the soil and if possible, maintain it around 5.5. It has been found that Japanese irises grow very well in heavy soils. Therefore, if the soil in your garden has a sandy texture or is somewhat light, you need to add lots of humus or rich compost to fulfill the requirements of the Japanese irises. In general, Japanese irises are heavy feeders and, therefore, it is essential to add organic materials to the soils on a regular basis, as it will help in promoting robust growth. If you are growing Japanese irises in places having cooler climatic conditions, it is important to provide them with organic mulches having low pH like pine needles, oak leaves, bark chips, sawdust, wood chips or properly decomposed or dried manure throughout the year. Such organic mulches will help to retain moisture, putting off weeds and also nourishing the plants. If you are using wood chips or sawdust, you should know that the process that involves the decomposition of these organic substances uses nitrogen from the atmosphere. Therefore, it is essential to augment the nitrogen content in the fertilizer program. However, you should be cautious while using organic mulches in places having hot summers, as these substances may promote fungal diseases like rot in places where there is too much heat and humidity. A number of experts have raised concerns over the fact that using chemical or artificially made fertilizers may possibly slow down the growth of Japanese irises, especially those that have been planted freshly. However, chemical fertilizers or organic ones are vital to ensure the robust growth of as well as excellent flower production by Japanese irises when they have already established themselves and also developed plenty of new roots. On the whole, you should apply fertilizers as well as organic mulches approximately three to four weeks prior to the flowering season. These should be applied for a second time roughly a month prior to the start of the fall, when new root growth takes place. Earlier, gardeners were of the view that they could grow Japanese irises successfully only close to any permanent water body such as bogs, ponds, lakes and streams. However, this conception is not wholly correct. However, the fact remains that Japanese irises do need copious amounts of moisture during their growing season. If you want your Japanese irises to produce large, beautiful blooms, it is important to provide them with lots of water from spring when the first new growths take place until about four weeks to six weeks after the flowering season. In order to grow and multiply vigorously, Japanese irises require adequate amounts of moisture as well as nutrients. Providing them with sufficient water and feeds will ensure the development of buds in the next spring and also adequate nutrient storage in the rhizomes. Usually, the new plants go into a dormant phase during the summer. You need to reduce watering the plants at this time of the year and, at the same time, ensure that the soil does not turn dry. The roots begin to grow actively at the onset of the fall with the objective to store enough nutrients and water that will help the plants to survive through the winter months and also promote new growths in spring. Therefore, it is essential to provide the plants with many heavy waterings during the fall, especially when there is insufficient rainfall. You should water the plants provided there is no rain for about a fortnight. At the same time, inspect the soil with your hand from time to time to ensure that it does not dry out completely. Spring or fall is the best time for planting Japanese irises straight away into your garden. These are the periods when the root growth is most active. In fact, it will be easier for the home gardeners to transplant Japanese irises immediately after the flowering season, when the roots are growing vigorously. The active root growth during the fall is the time when commercial growers actually ship the Japanese irises to ensure that the plants arrive much before the first expected frost. If you are growing the Japanese irises in your garden, plant the irises in a shallow hole in the soil so that they can hold water. At the same time, initiate measures to reduce overflow and ensure that the roots are embedded deep into the soil. To ensure the proper reestablishment of the rhizomes, it is necessary to keep them moist all the time. On the other hand, you may also growing Japanese irises in containers, instead of planting them into the garden straight away. Planting the irises initially in containers will help them to build up an excellent root system. Subsequently, transplant the irises in their permanent places outdoors into the garden during spring. After having established the Japanese irises in containers, you can transplant them in your garden whenever you wish. Irrespective of the Japanese irises are in pot thrust into the soil, in the soil, or even in pots placed in plastic pools, you need to provide them with protection against the harmful freezing and thawing successions, which afflict the plants during the winter months. In case neither the climatic conditions in your region nor the soil in your garden is suitable, it is advisable that you grow Japanese irises in containers/ pots either outdoors or indoors. Use a potting soil that is acidic or prepare your own mix using a highly acidic, organic medium. Ensure that the pots have a diameter of no less than 6 inches - pots with bigger diameter are better. Place the pots in a pan with some shallow water to ensure that the pots never become completely dry. If you grow the potted Japanese irises outdoors, remove them from the wadding pools or water pans during the winter and shelter the plants by thrusting them into the soil. In addition, apply heavy mulching on the ground where you have plunged the plants. Japanese irises need to be divided once in three to four years. As the rhizomes grow and become mature, they come closer to the surface of the soil and very soon they will rise higher than the soil surface and be short of sufficient moisture. In the absence of adequate water, the roots will start diminishing and may also wither away. If you notice the rhizome growing out of the soil, excavate the iris plant, transplant it in a pot for a while and provide it with lots of water. It is possible that this treatment will help the plant as well as its rhizome start fresh growth. If you are residing in an area where the soil as well as water have a propensity to be too alkaline, you need to examine the soil from time to time with a view to know its pH. This is essential if you want your Japanese iris plants to flourish and produce standard blooms. In fact, testing the soil for pH on a regular basis should essentially be included in your regimen. Don't lose heart or give up even if the soil or climatic conditions in your area do not conform to the requirements for growing Japanese irises. Despite such deficiencies, you can grow Japanese irises in pots or in elevated beds. Make an acidic planting mix or medium for use in pots or the plant beds by including lots of sphagnum peat moss or other organic substances that are acidic in nature or having a pH below 7.0.


The Japanese iris produces flowers that are of a single form, having as many as three erect standards and relatively longer falls that are in a pendent position. Japanese as well as numerous purists still admire this classic form of the species very much. However, often it is seen that the hybridized varieties have double form. They have large standards that are of the same size as well as appearance as the falls, which are wide and positioned horizontally. Together with their six petals, these make the flowers appear large and flat, nearly having a circular form. At times, the petals are frilled along their margin. A number of hybrids developed in contemporary times show further deviation from their parent plants. They bear flowers which have numerous petals or a peony form, which includes over six "petals" and impart a fuller form to the flowers. A tetraploid cultivar is defined as a plant that has been engineered in a manner that its chromosome count will be double that of the standard plants. The first tetraploid cultivar of Japanese was bred in the United States in 1960 by Currier McEwen. It was developed from the species called I. ensata. Since 1979, tetraploid cultivars of Japanese iris were readily available, as an increasing number of breeders were successful using this method. Therefore, the collection of plants bearing flowers with exotic features has also increased. In fact, when we say that the range of the flowers of Japanese irises comes in a variety of hues like white, mauve, blue, pink and purple, it may seem to be quite limited. However, we also need to consider that they also come in a wide range of patterns. Majority of falls of the Japanese iris blooms have a striking characteristic yellow signal. The yellow signal on Japanese iris blooms is actually a replacement of the beards that are seen on tall bearded irises. Apart from the typical yellow signal, Japanese iris flowers may also have fine veins, which are like delicate dark lines. Alternatively, they may also be sanded - having small dark dots along with very small broken lines. Some Japanese iris flowers may also have an outline around the petals and falls or may appear to be brushed with tiny spots. Others may also have bold white markings.


The blooming season of Japanese irises continues well beyond the flowering season of the other plants in the same genus. Even after the tall bearded irises have completed blooming for the season and people wait for the flowers to appear again a year later, the Japanese irises continue to exhibit their exquisiteness. In fact, this iris variety continues to flower even after the Siberian irises have nearly completed their first flowering of the season. Therefore, it is prudent to choose a group of Japanese irises that bloom from the early season to late in the season, as it will enable the gardeners to take delight in beautiful flowers throughout the flowering season, which usually lasts for roughly six weeks. A number of Japanese iris cultivars also bloom for a second time in the same season. This usually occurs roughly three weeks after the blooms of the first flush have died down. Therefore, you may find that some Japanese iris plants may produce seedpods as well as flowers simultaneously. In fact, the second flowering of a plant, known as remontancy in botanical terminology, is subject to its growing conditions. Nevertheless, it also involves a genetic trait of the plant.


I. ensata (syn I. kaempferi)
Most of the iris cultivars bred by the Japanese have been derived from the parent species called Iris ensata. Plants derived from this iris species produced large flowers, characterized by their intensely ridged dense foliage. I. ensata is not a particularly bog plant or prefers water. On the contrary, it has a preference for a fertile and properly drained soil. Nevertheless, this iris species needs plenty of water during spring as well as the beginning of summer. I. ensata developed for growing in gardens should essentially be provided with a fertile and rich soil having a perfect drainage. I. ensata is a fairly tall iris species, growing up to 42 inches (1.3 meters) in height. The flowering stalks of this plant grow higher than its foliage. The color of this species' blooms vary - ranging from deep red-purple to white and sometimes they also occur in shades of blue. The fall has a golden stripe in the middle.
Irises Aril and Arilbred Irises Bearded Irises / Culture / Species Bulbous Irises Evansia or Crested Irises Louisiana or Hexagona Irises Median Irises Miniature Dwarf Bearded Irises Novelty Bearded Irises Pacific Coast or California Irises Reticulata or Dwarf Bulbous Irises Scorpio or Juno Irises Siberian Irises Spuria Irises Tripetala Irises