Plant & Flower Identification

Japanese Iris Vs Siberian Iris – How Are They Different?

When it comes to elegant and captivating iris flowers, the Japanese Iris and Siberian Iris are two distinct varieties that deserve special attention.

How are they different? Delve into the world of Japanese Iris vs Siberian Iris to explore their divergent traits, growth habits, and ideal cultivation conditions.

Whether you’re an avid gardener or admire these beautiful blooms, knowing their distinctions can help you choose the most suitable one.

What Are The Similarities Between Japanese Iris And Siberian Iris? 

japanese iris vs siberian iris


Japanese Iris and Siberian Iris are famous for their stunning and vibrant blooms. They have various colors, including shades of blue, purple, white, and pink.

The colorful flowers of both species have a similar shape, with three large outer petals known as falls and three smaller inner petals called standards.

These intricate and delicate floral structures make them visually appealing additions to any garden.


The two reach a similar height, ranging from 3 to 4 feet tall. This moderate height allows them to stand out among other plants without overpowering the landscape.

Their tall stature adds a unique element to any floral arrangement or garden bed.


Both types contain toxins that can be harmful if ingested. These toxins are primarily concentrated in the rhizomes of the plants.

Therefore, you should be cautious, especially if children or pets are nearby. It’s best to keep these plants out of reach and handle them carefully.


Regular fertilization can support the reblooming capabilities of these beautiful flowers.

In early spring, it is recommended to fertilize them with a low-nitrogen, phosphorus, and potassium-rich fertilizer, such as a 5-10-10 formula.

The frequency of fertilizing should be every four weeks during the spring and summer seasons.

It’s important to avoid fertilizing during the fall and winter months and ensure the fertilizer does not come into direct contact with the rhizomes.

What Are The Differences Between Japanese Iris Vs Siberian Iris?

bearded iris vs iris

Siberian irises are generally more colorful, larger in size and can adapt to wetter soils and a wide range of soil pH.

Their leaves will stay upright with a striking blueish cast under the light, while Japanese ones tend to flop over.


Japanese irises typically grow to a height of 24 to 30 inches with a width of about 24 inches.

These Iris plants are known for their moderate size, making them suitable for various garden settings. Their height and width contribute to their overall presence in the landscape.

Siberian irises are generally larger than Japanese ones, reaching a height of 24 to 36 inches with a similar width of 24 inches.


Japanese irises show a wide range of colors, including shades of blue, purple, white, and pink. These vibrant hues make them captivating and offer a diverse palette for garden design.

Siberian irises display more colors. In addition to blue, purple, white, and pink, they have yellow, red, and orange colors. In shifting light, their leaves may reveal a slight bluish-green cast.


The leaves of Japanese irises are sword-shaped and narrow, with tips that gracefully flop over. They possess a distinctive appearance with a prominent midrib vein.

Their leaves’ jade to Kelly green color further enhances their elegance and beauty.

Siberian irises also have sword-shaped, narrow leaves, but their tips maintain an upright position. The leaves exhibit similar characteristics to Japanese irises, with jade to Kelly green color.

However, the bluish cast in shifting light makes their foliage more attractive.


Japanese Iris leaves tend to flop over, gently creating a graceful and flowing habit. This habit adds a soft and artistic touch to the plant’s overall appearance, making it a delightful addition to gardens.

Siberian Iris leaves maintain a more upright posture, giving the plants a sturdier and more erect overall habit. The upright growth habit provides a sense of structure and strength.



Japanese and Siberian irises are planted by creating trenches and placing the rhizomes on a ridge.

However, the Japanese Iris prefers good drainage in the soil, while Siberian Iris is more tolerant of wet feet.

This difference in planting preferences reflects their varying needs for moisture and soil conditions.

Soil Condition

Both types of irises benefit from soil enriched with organic matter. Japanese Iris requires well-drained soil to avoid waterlogging, while Siberian Iris can tolerate wetter soil conditions.

Besides, the Japanese Iris thrives in slightly acidic soil (pH ranging from 5.5 to 6.5).

Meanwhile, Siberian Iris can adapt to a wider range of soil pH levels (6.0 to 7.0). It prefers slightly acidic to neutral soil, which helps them grow well in alkaline or acidic soils.

Light Requirement

Japanese Iris tends to produce more spectacular blooms under full sun conditions, while Siberian Iris can tolerate partial shade, although it may result in fewer blooms.

Besides, you should have them gain at least six hours of sunlight daily to promote healthy growth and abundant flowering.


Proper watering is crucial for both irises, but their specific requirements differ. Japanese Iris needs regular watering to maintain moist, but not soggy, soil.

On the other hand, Siberian Iris is more drought-tolerant once established and can withstand periods of dryness.

However, providing even moisture to both types will result in healthier and more vigorous growth.

Deadheading & Trimming

Siberian Iris does not really require deadheading and generally does not need regular trimming. Meanwhile, like butterfly bushes, the Japanese iris benefits from deadheading.

It will promote continuous blooming and may require selective trimming to maintain a neat appearance.

However, regularly removing faded flowers will encourage the development of new flower buds. Avoid cutting back all the foliage, as this Iris relies on healthy leaves to capture sunlight for photosynthesis.

What Are The Pests And Diseases Of Siberian Iris Vs Japanese Iris? 

siberian iris vs japanese iris

Leaf Spot 

Leaf spot is a fungal disease that causes circular spots on the leaves of irises. I notice that both the Japanese Iris and Siberian Iris can be susceptible to leaf spots.

The spots initially appear yellow and turn tan or brown with a red halo in my iris garden. While leaf spot does not usually cause the death of irises, it can weaken the plants over time.

Control measures for leaf spot include:

  • Promptly removing all infected leaves.
  • Avoiding overhead watering, which can facilitate the spread of the disease.
  • Providing adequate spacing between plants promotes air circulation and faster drying of leaves.

Soft Rot

Soft rot is a bacterial disease caused by Erwinia Carotovora. It primarily affects the rhizome and lower leaf sheath, causing them to rot and turn black and mushy.

A foul smell often accompanies the presence of soft rot. The bacteria enter the rhizome through wounds in the plant.

I apply these preventive measures against soft rot:

  • Planting the rhizomes at the correct depth ensures they are barely covered with soil.
  • Avoiding excessive moisture around the rhizome.
  • Discarding severely affected rhizomes and planting irises in a different location.
  • Allowing the soil to dry out before replanting irises in the same area.

Iris Borers

Iris borers are the larvae of moths that lay eggs in old plant debris during the fall. The larvae tunnel into the leaves and the rhizomes, causing extensive damage.

Additionally, their entry points provide opportunities for soft rot to develop.

Control measures for iris borers include:

  • Removing and destroying old leaves, plants, and foliage in the fall to eliminate overwintering sites for the eggs.
  • Applying a pyrethrin-based pesticide when the leaves are around five to six inches long targets the hatching larvae.


What Are The Differences Between Dutch Iris Vs Siberian Iris?

AspectDutch IrisSiberian Iris
AppearanceLarge, showy flowers with blue, purple, yellow, and white colorsSmaller, elegant, violet, blue, red, white, purple, or orange flowers.
Plant SizeAround 18-24 inches tallReach a height of 24-36 inches
Leaf ShapeNarrow, sword-shaped leavesLong, slender leaves with a grass-like appearance
Growing ConditionsDutch iris prefers well-draining soil and full sun to partial shadeTolerates a wider range of soil conditions and can thrive in moist or even acidic, neutral, and boggy soil.
Flowering TimeBooms in late spring to mid-summer or maybe later if you plant Dutch Iris in spring.Blooms in early to mid-summer

What Are The Differences Between Dutch Iris Vs Bearded Iris?

AspectDutch IrisBearded Irises
AppearanceLarge, showy flowersVarious colorsBroad, ruffled petalsFuzzy “beard” on petals
Bloom TimeBooms in late spring to mid – summerLate spring
Leaf ShapeNarrow, sword-shapedBroad, upright petals and leaves
Plant Size18-24 inches28-40 inches
FragranceNot strongly fragrantOften has a strong fragrance
RhizomeBulbous root structureThick, fleshy rhizome

Blue Flag Iris Vs Siberian Iris – How Are They Different?

AspectBlue Flag IrisSiberian Iris
AppearanceMedium to large flowersViolet-blue to purple petalsMedium-sized flowersVarious colors, including blue, purple, white, and yellow
Growing conditionThrives near water bodiesTolerant of boggy conditions
USDA ZoneZones 3-9Zones 2-9
FragranceMildly fragrantNot strongly fragrant
Leaf ShapeSword-shaped, erect leavesNarrow, sword-shaped leaves
Natural HabitatNative to AmericaNative to Europe and Asia
Pests and DiseasesLeaf spotIris borersLeaf spotSoft RotIris Borers 
AdaptabilityCan tolerate some droughtCan tolerate drought and excessive moisture


In conclusion, the Japanese Iris vs Siberian Iris are two distinct species that offer unique characteristics and qualities.

Understanding these different kinds of Irises can help gardeners choose the most suitable iris variety for their growing conditions and preferences.

Whether it’s the elegance of the Japanese Iris or the adaptability of the Siberian Iris, both species contribute to the beauty and diversity of the iris family.

Samuel Mark

Hello I am Samuel. Samuel's Garden is a garden blog where I share my experiences in garden caring and tree growth. Hope you enjoy it!

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