Japanese iris Iris ensata 'Kozasa Gawa'

☠ Toxic to humans
🐾 Toxic to pets
🌸 Blooming
🍪 Not edible
‍🌱 Hard-care
Japanese water iris 'Kozasa Gawa'


The plant known as the Japanese iris 'Kozasa Gawa' showcases a stunning display of large, ornate flowers that are distinguished by their vibrant purple-blue hues and intricate patterns. Each bloom consists of several layers of petals, with the outer falls splaying gracefully downwards, often featuring a delicate white to yellow signal at the base. The standards, or upright petals, rise majestically above the falls, adding dimension and depth to the exquisite flower. This variety is known for its bold coloring and the velvety texture of its petals, which can captivate the attention of any onlooker. The foliage of 'Kozasa Gawa' is equally striking, with long, sword-like leaves that create an elegant, vertical accent in the garden. These leaves are a rich green color, contributing to the plant's lush appearance and providing a striking backdrop for the dramatic blooms. The leaves are arranged in a fan-like fashion, emanating from the base of the plant and producing an organized, yet natural, structure. Together, the spectacular blooms and attractive foliage of the Japanese iris 'Kozasa Gawa' provide a breathtaking display that's cherished by gardeners and flower enthusiasts alike. Its presence in a landscape or garden setting can add a touch of sophistication and an infusion of vibrant color that's especially appealing during its blooming season.

Plant Info
Common Problems

About this plant

  • memoNames

    • Family


    • Synonyms

      Japanese Iris, Hanashobu.

    • Common names

      Iris ensata 'Kozasa Gawa'.

  • skullToxicity

    • To humans

      The Iris ensata 'Kozasa Gawa', commonly known as Japanese iris, is not typically considered highly toxic to humans. However, it may contain compounds that can cause stomach discomfort if ingested in significant quantities. Eating parts of the plant, like the rhizomes, may result in symptoms such as nausea, vomiting, abdominal pain, or diarrhea. Handling the plant may also cause skin irritation in sensitive individuals. It is always advisable to avoid ingesting any part of ornamental plants and to keep them out of reach of children who might accidentally consume them.

    • To pets

      The Iris ensata 'Kozasa Gawa', commonly known as Japanese iris, is considered mildly toxic to pets if ingested. The main concern is with the rhizomes, which contain irritant substances that can lead to gastrointestinal upset. If a pet ingests part of the plant, they may experience symptoms such as vomiting, drooling, lethargy, or diarrhea. In more severe cases, ingestion can result in more serious signs like abdominal pain. It is recommended to keep this plant away from pets and to consult with a veterinarian if any part of the plant is ingested by an animal.

  • infoCharacteristics

    • Life cycle


    • Foliage type


    • Color of leaves


    • Flower color


    • Height

      3 feet (91 cm)

    • Spread

      2 feet (61 cm)

    • Plant type


    • Hardiness zones


    • Native area



  • money-bagGeneral Benefits

    • Ornamental Appeal: Iris ensata 'Kozasa Gawa' provides striking blooms that enhance the aesthetic of gardens and landscapes.
    • Water Garden Suitability: Well-suited for water gardens or along the edges of ponds due to its preference for moist soils.
    • Pollinator Attraction: Attracts pollinators such as bees and butterflies, contributing to the health of the garden ecosystem.
    • Low Maintenance: Once established, this plant requires minimal upkeep beyond occasional division to manage its size.
    • Cultural Significance: In Japan, irises like Iris ensata hold cultural importance and are often featured in gardens and art.
    • Erosion Control: The robust root system can help stabilize soil and prevent erosion, especially in moist, water-logged areas.
    • Seasonal Interest: Provides interest throughout its growing season with lush foliage before and after the flowering period.
    • Diversity in Garden Design: Adds a unique texture and shape to garden designs, thanks to its sword-like leaves and intricate flowers.

  • medicalMedical Properties

    This plant is not used for medical purposes.

  • windAir-purifying Qualities

    This plant is not specifically known for air purifying qualities.

  • leavesOther Uses

    • Iris ensata 'Kozasa Gawa', commonly known as Japanese iris, can be used in fabric dyeing, offering a range of colors from yellows to purples depending on the mordant used.
    • The fibrous leaves of Japanese iris can be woven into ropes, mats, or even sandals in traditional crafting techniques.
    • The stems of the Japanese iris, being sturdy and straight, can serve as natural floral stakes in the garden to support other, more delicate plants.
    • Japanese iris can be utilized as a natural indicator plant for waterlogged soils, as they thrive in moist conditions, signaling the garden's wet areas.
    • They can provide a habitat and nourishment for beneficial insects, including bees and butterflies, aiding in pollination within the garden.
    • The blooms can be used for artistic inspiration, influencing designs in painting, photography, and fabric patterns due to their unique shape and colors.
    • Floral arrangements benefit from the height and structure of Japanese iris stems, which add vertical interest to compositions.
    • Japanese iris can contribute to the organic matter in soil when their leaves and stems are left to decompose, thus improving soil health.
    • The vibrant flowers can be floated in bowls of water as a decorative centerpiece for outdoor garden parties or serene indoor settings.
    • Culinary presentations can be embellished with Japanese iris flowers, as the non-toxic blooms can be placed as garnishes on plates, though they are not intended for consumption.

Interesting Facts

  • bedFeng Shui

    Japanese Iris is not used in Feng Shui practice.

  • aquariusZodiac Sign Compitability

    Japanese Iris is not used in astrology practice.

  • spiralPlant Symbolism

    • Wisdom - The iris is often associated with wisdom due to its stately appearance and has been historically linked to deities of wisdom.
    • Hope - As a spring flower, the iris symbolizes hope and the renewal that comes with the changing of seasons.
    • Trust - The iris can represent trust, conveying a message of faith and assurance.
    • Purity - With its delicate form and often white coloration, the iris can be a symbol of purity.
    • Courage - In some cultures, the bold nature of the iris stands for courage and valor.
    • Royalty - Due to its regal appearance, the iris is frequently associated with royalty and majesty.

Every 2-3 days
2500 - 10000 Lux
Every year
Late Summer
Not needed
  • water dropWater

    The Japanese Iris, or Iris ensata 'Kozasa Gawa', thrives in consistently moist soil, particularly during its growing season in spring and early summer. Water deeply once or twice a week to maintain an adequate moisture level, avoiding shallow sprinklings that don't reach the roots. Aim to provide approximately 1 to 1.5 gallons of water per plant each week, adjusting for rainfall and temperature conditions. During hot, dry spells, you may need to water more frequently to prevent the soil from drying out. In the late summer and fall, after the blooming period, you can reduce the watering frequency as the plant’s water needs decrease.

  • sunLight

    Japanese Iris prefers full sun to partial shade, with at least six hours of direct sunlight each day to flourish. The ideal spot would be one where it receives morning sun and protection from the intense heat of the afternoon sun, which can be provided by light-filtering trees or structures. However, if the plant is in an area with cooler summer temperatures, it can tolerate full sun all day.

  • thermometerTemperature

    The Japanese Iris performs best in temperatures between 55°F and 75°F. It can survive winter cold down to about -20°F, but for optimal growth and flowering, ensure it isn't exposed to temperatures above 90°F for prolonged periods. The cooler temperatures of early spring and fall are particularly favorable for this plant.

  • scissorsPruning

    Prune the Japanese Iris by removing dead or damaged foliage and spent flower stalks to promote healthy growth and appearance. This is best done after the blooms have faded, usually in late summer. Cutting back the foliage to the ground in late fall after the first frost helps to tidy up the plant and remove any diseased leaves, reducing the likelihood of pests and disease in the following growing season.

  • broomCleaning

    As needed

  • bambooSoil

    Japanese Iris requires acidic to neutral soil with a pH of 5.5 to 7.0. For optimal growth, mix garden soil with peat moss and compost to ensure rich, moist conditions, particularly if aiming for a bog-like environment which this species favours. Ensure good drainage as stagnantly wet soil may cause rot.

  • plantRepotting

    Japanese Iris typically does not require frequent repotting and can be left undisturbed for several years. It may be beneficial to divide and repot these irises every 3-4 years to prevent overcrowding and to maintain plant vigour.

  • water dropsHumidity & Misting

    Japanese Iris thrives in environments with high humidity, mirroring their natural wetland habitats. Aim for a humidity level that is consistently moist but not saturated, avoiding dry air that may stress the plant.

  • pinSuitable locations

    • Indoor

      Use moist, well-draining soil and bright, indirect light.

    • Outdoor

      Plant in full sun to partial shade in moist soil.

    • Hardiness zone

      4-9 USDA

  • circleLife cycle

    Iris ensata 'Kozasa Gawa', commonly known as Japanese iris, begins its life cycle when the rhizomes are planted in fertile, acidic, moist soil, typically in spring or fall. The plant emerges with long, slender leaves and develops a strong root system that anchors it into the ground. During the growing season, it forms tall stems that bear the distinctive large, ruffled flowers, which are often purple or blue with yellow or white markings, blooming in late spring to early summer. After flowering, the plant sets seed in a capsule if pollination has occurred, although many gardeners remove spent blooms to encourage vigor. Throughout the summer, the foliage remains lush and is followed by senescence in fall as the plant enters dormancy in preparation for the winter months. The cycle renews in the next growing season, with new growth emerging from the rhizomes as temperatures rise.

  • sproutPropogation

    • Propogation time

      Late Summer

    • The Japanese Iris or Iris ensata 'Kozasa Gawa' is most commonly propagated through division, which is typically done after the flowering season, late summer to early fall. To propagate by division, carefully lift the clump of the iris from the ground and use a sharp, clean knife to separate the rhizomes, ensuring each section has at least one fan of leaves and healthy roots. These divisions should then be replanted at the same depth they were growing at previously, and spaced about 12 to 24 inches (30 to 60 cm) apart to allow for growth. Water the new divisions well to help establish them. This method helps to rejuvenate older clumps that may have become too crowded, resulting in poor flowering, and is an easy way to increase the number of irises in your garden.