Purple Dutch iris bloom in the spring and summer from rhizomes planted in the fall or spring. With blossoms that are smaller than bearded iris and larger than dwarf iris, Dutch iris flowers fit beautifully into a medium-sized bouquet. Foliage shows up in your garden three to four months before the plants actually bloom. The flowers last between one and two weeks, but each stem may produce more than one blossom at a time. Hardy in zones 5 through 9, purple Dutch iris will grow in your garden or in containers
Dig a 4- to 6-inch deep trench in a sunny location of your garden. Purple Dutch iris prefer full sun and well-drained soil, but you can also grow them in partial shade. If you plan to plant more than one iris, separate them 4 to 6 inches apart.
Create a 1- to 2-inch tall ridge with soil in the center of the trench. A soil ridge is a pile of soil that creates a divide in the trench. The ridge should be about 1-inch wide. The exact height of the ridge will vary based on the length of the rhizome. Place the Dutch iris rhizome on top of the ridge with the pointed side facing up. The top of the rhizome should be within 1 inch of ground level. Spread the roots on both sides of the ridge. This planting method will encourage the iris to spread in the same direction without fear of becoming crowded too soon.
Fill in the trenches around the roots with soil. Cover the top of the rhizome with soil. Water the newly planted rhizomes thoroughly. Dutch iris do not like wet feet, but need an average amount of watering through the growing season. Do not water the plant while it is dormant.
Fertilize the soil around the planted purple Dutch iris with bone meal and a low nitrogen fertilizer in the spring.
Cut the flowers as desired as they bloom; this will not hurt the plant. Leave the foliage intact after the blooms end. At summer's end, the foliage will yellow; remove the leaves at this time as the plant slips into dormancy.
Propagate purple Dutch iris one month after flowering if the clumps are becoming crowded. Remove the rhizomes with a garden fork and divide the clump into single rhizomes by hand. Replant the rhizomes.