Iris japonica is very common in cultivation in USA, it is the most commonly cultivated crested iris in the UK.

It is hardy to between USDA Zone 7 to Zone 10.
It is also hardy to European Zone H3.
It is very easy to grow in a Mediterranean climate in sheltered positions.

Within the UK, it is hardy in Devon and Cornwall, and some other parts of southern UK.
It prefers the protection of a sheltered sunny wall.
Some cultivars of Iris japonica are more hardy than others.
However, an extremely cold winter (or late frosts) may adversely affect the flowering of this species, and the foliage becomes tatty, or browned.

It should be grown in well-drained soils, but moist soils are preferred.

It can tolerate neutral or acidic soils (PH levels between  6.5 – 7.8).,
though prefers slightly acidic soils (including peat banks).
It is not tolerant of salty water.

It has average water needs during the growing season, wet or damp conditions during the winter may cause the root to rot.
It can tolerate positions between full sun and partial shade, but prefers partial shade.

It can be grown in a mixed flower border, as a ground cover plant and can be also grown in containers in sheltered positions.

In frost prone areas, it can be grown in a cool greenhouse.
The plants are rested in summer (after the spring flowering), and then started again in the late autumn.
If it cannot be grown in a cool house, it should be given a sheltered position, with shrubs where it is protected from the morning sun.

The stems and dead leaves should be removed after flowering to keep the plant tidy and help it, for next years growth.

It does not have any serious disease or insect problems, but pests (such as Thrips, slugs and snails), occasionally damage plants by feeding on the flowers or foliage.
Aphid Aulacorthum magnoliae can be found on the plant.
It can be susceptible to attack by Japanese Beetle.
Iris japonica is very common in cultivation in USA, it is the most commonly cultivated crested iris in the UK.
It is hardy to between USDA Zone 7 to Zone 10. It is also hardy to European Zone H3. It is very easy to grow in a Mediterranean climate in sheltered positions.
Within the UK, it is hardy in Devon and Cornwall, and some other parts of southern UK. It prefers the protection of a sheltered sunny wall. Some cultivars of Iris japonica are more hardy than others. However, an extremely cold winter (or late frosts) may adversely affect the flowering of this species, and the foliage becomes tatty, or browned.
It should be grown in well-drained soils, but moist soils are preferred.
It can tolerate neutral or acidic soils (PH levels between  6.5 – 7.8)., though prefers slightly acidic soils (including peat banks). It is not tolerant of salty water.
It has average water needs during the growing season, wet or damp conditions during the winter may cause the root to rot. It can tolerate positions between full sun and partial shade, but prefers partial shade.
It can be grown in a mixed flower border, as a ground cover plant and can be also grown in containers in sheltered positions.
In frost prone areas, it can be grown in a cool greenhouse. The plants are rested in summer (after the spring flowering), and then started again in the late autumn. If it cannot be grown in a cool house, it should be given a sheltered position, with shrubs where it is protected from the morning sun.
The stems and dead leaves should be removed after flowering to keep the plant tidy and help it, for next years growth.
It does not have any serious disease or insect problems, but pests (such as Thrips, slugs and snails), occasionally damage plants by feeding on the flowers or foliage. Aphid Aulacorthum magnoliae can be found on the plant. It can be susceptible to attack by Japanese Beetle.
Iris japonica