Things You'll Need
5-10-10 ratio fertilizer
Dutch iris is a name given to several hybrid varieties of Spanish iris, or Iris xiphium, which are grown for their ornate, bicolored flowers and graceful foliage. Like all species of irises, Dutch irises require thinning every few years to provide the bulbs with new soil and enough room to grow. The bulbs are easy to dig up and transplant in late summer following their blooming period, but you must wait until after the plants have lost their leaves for the season before moving them.
Transplant Dutch irises in late summer, once the foliage dries out completely and turns yellowish brown. Allow the foliage to dry out completely since the bulbs need to acquire as much nutrition as possible in order to bloom the following year.
Measure out 2 inches from the base of each Dutch iris plant. Dig 5 inches deep around the base of the dried foliage using a garden trowel.
Lift the Dutch iris bulbs from the ground. Pull off and discard the dry leaves. Store the bulbs until autumn, or transplant them immediately into the garden.
Transplant the Dutch iris bulbs into a new bed with the same conditions as the original bed. Space the bulbs 3 to 6 inches apart. Plant them to a depth of 4 to 5 inches.
Allow the bulbs to rest for the remainder of the growing season without watering or fertilizing them.
Watch for sprouting the following spring around mid-April. Feed the Dutch iris plants with 5-10-10 ratio fertilizer once the leaves grow to 3 inches in height.
Do not transplant Dutch iris plants when the leaves are green or the plants are blooming.