The word on the street (I’ve always wanted to say that) is that the Dutch iris is a short-lived perennial. Tell that to Romano an incredible showy bloomer that we have in the garden which was planted in the late 1990s. I’ve led a life comparable to a house flipper so my personal experience on the longevity of perennials has been word of mouth or reference book to say the least, but it seems to me anything approaching 20 years would rate as awesome.
The Dutch iris has been relatively trouble free here in Savannah and our variety Telstar which is blooming now has cameras snapping. It has been in the ground three years is naturalizing wonderfully well. They are so beautiful and easy to grow I told Stan Gray of Gray’s Iris fame that in addition to all of the thousands of Louisiana irises he is planting we need every Dutch iris we can get our hands on.
That is when my eyes were opened to the complexity of this group. First off when I typed it in my favorite search engine it came back asking if I meant Dutch Irish? Holy ancestry! Then when I convinced the search engine to realize I was talking about plants I quickly came to realize this is the most famous florist iris for cut-flowers. Then I typed in Iris hollandica and Iris x hollandica the names on our tags, nope, even those are not officially recognized.
To cut to the chase, the Dutch iris a group originated in Spain, Morocco, Portugal and other Mediterranean countries with the Iris xiphium. The resulting hybrids with I. tingitana and I. latifolia and I. lusitanica have resulted in garden bulbs that will bloom with both rare beauty and structure.
The Dutch iris is a bulb versus a rhizome. Most references suggest a cold hardiness of Zones 6-9 but it’s not hard to see gardeners touting a return in zone 5 when a protective layer of mulch has been added. They need plenty of sun to bloom their best, though a little afternoon shade would be tolerated.
The soil should be fertile and very well drained. It stands to reason if I am raving about their beautiful blooms now, fall is the best time to plant. It is possible you may find container grown plants this spring in which case take advantage and get them established in your landscape.
Otherwise, you will want to plant bulbs 3-to-5 inches deep. Almost every reference suggests planting them 3-to-5 inches apart or up to 12 bulbs per square foot. In Savannah our plants are vigorous, reaching 36 inches so a wider spacing of 8-to-12 inches makes me a little more comfortable. Massing your planting will definitely give the best show. Leave the foliage until it dies after the bloom, much like you do a daffodil. This ensures sufficient energy for next year’s blooms.
If the dying foliage is problematic for your display, plan for their disguise. For instance, if you look at our blooming Telestar iris now, you see a blooming loropetulm, and the blue fruited mahonia. What you don’t see are the perennials that will come up screening the old iris foliage. One of my friends in Mississippi created quite a showy display with the exquisite Wedgwood Dutch iris, Louisiana phlox and daffodils. It’s really simple just plan for a rotation of color through the seasons.
In the garden, we have Louisiana irises, tall-bearded irises, spuria irises, psuedata irises, native irises and Japanese roof irises but I can tell you when the Dutch irises are blooming they will compete for camera time.