The Dutch iris plant (Iris xiphium) grows to heights between 15 and 24 feet with an equal spread at maturity. Healthy specimens produce grassy foliage that gives way to showy white, orange, purple, blue, yellow or rose-coloured flowers that bloom in spring. Grown from bulbs, the Dutch iris thrives when planted in USDA hardiness zones 6 through 9, where winter temperatures don't drop below -23.3 degrees Celsius. Gardeners who wish to plant Dutch iris in the backyard landscape can do so by burying bulbs in the early fall.
Prepare the soil for planting in late September or early October. Break up the soil using a garden fork and test the pH using a simple soil-testing kit from a garden centre. Dutch iris prefers soil with a pH between 5.0 and 7.5.
Raise the soil pH if it is below 5.0 using lime. For soil with a pH above 7.5, add peat moss. Mix in the required amendment according to label instructions.
Dig holes for the Dutch iris bulbs that measure four inches deep. Space the holes at least three inches apart. Deposit one Dutch iris bulb in the centre of each hole, pointed side up.
Water-in the Dutch iris bulbs after planting. Soak the soil to a one-inch depth, watering weekly until the first frost, using a garden hose. Discontinue watering in the winter.
Resume weekly watering in the spring when the bulbs sprout. Pinch off dead blooms as the Dutch irises grow to encourage further blooming. Snip the stems for bouquets as often as desired throughout the growing season.
Allow the Dutch iris bulbs to die back naturally in the fall. The foliage will go from green to yellow and finally to brown when the dieback process is over. Cut the foliage to the soil line using a lawnmower or pruning tool. The Dutch iris bulbs will re-emerge in spring.
Dutch irises also grow well in pots. Plant five bulbs in an eight-inch pot filled with organic potting soil or seven bulbs in a 10-inch pot. Dutch iris bulb spacing in pots should always be at least three inches with the bulbs planted at a depth of two inches. Set the pots in a sunny location, keeping the soil moist at all times.
Do not remove the Dutch iris foliage before the dieback process is complete. During dieback, the leaves soak up energy from the sun and transfer it to the bulb. Removing the foliage before it turns brown may cause the bulb to yield fewer blooms in the spring.