Expert: Long Island Gardener - 5/14/2007

Question
2 1/2 years ago in November I bought this home. I moved a bunch of dutch iris to the side of the house and just sat them on the ground. I was afraid they would die. To my surprise they bloomed beautifully the following spring. That year I planted them where I wanted them, not far from where they were. The following spring they didn't bloom. So, I thought they needed to be divided. So, I split them up into three groups and added some iris of another color. This year, they came up..............but no blooms on any of them!! I read some where that they could be too deep or that they may need to establish themselves. Any experts out there on dutch iris?

Answer
Dutch Iris are fickle, as so many beautiful things are.  Moisture is a problem.  Depth is a problem.  Temperatures are a problem.  Sun is a problem.

When you moved the clump of Dutch Iris -- hybrids of Iris xiphium, Iris tingitiana and Iris latifolia -- intially, they had already built the next year's bloom.  As long as the moisture and cold exposure were not damaging, the Iris were cooperative.

But in their new location, something was not right.  Yes, it could be the depth, as you pointed out.  The vagaries of Dutch Iris growing are spelled out very well in the website for Dr. Leonard Perry, a professor at University of Vermont, under 'Pests and Problems': 'bacterial soft rot and leaf spot, botrytis blight, fungal leaf spots and rusts, rhizome and crown rots, blue mold, mosaic virus, aphids, iris borer, thrips, nematodes, grubs...'

There's more on the Zanthan Gardens website (http://www.zanthan.com/gardens/gardenlog/archives/000138.html): 'xiphium bulbs grow naturally in hot, dry summer conditions and unless you can provide soil that is hot and dry in summer and not overly cold in winter, the bulbs should be lifted...'  and 'I. xiphium will grow best in a heavy soil with good drainage...They enjoy an alkaline soil.' (quoting garden author and Iris expert Graeme Grosvenor in Iris: Flower of the Rainbow)

He has a LOT of trouble with these.  Which is not unusual, and maybe even typical.  Most people who run out of patience with a certain plant don't keep a public record of their surrender.  It's the people who succeed who are typing out the details of their learning experience.

Rutgers University Extension Service
(http://aesop.rutgers.edu/~greenmachine/comm_fl_design/CUT_FLOWERANDGREENSID/CUTF...)
devotes a page to Dutch Iris packed with directions on how to make them happy.  In a nutshell:  Perfect drainage is a necessity, the ideal soil measuring a pH of 6.0 or higher.  If your soil is heavy clay, it should be lightened with aged mushroom compost or manure and sand plus topsoil.  Full sun is a non-negotiable requirement.

Where are you on planet Earth, Robin?  Colder than Zone 5?  Warmer than Zone 6?  Is that soil pure Clay?  Is that Iris plot under a tree?  Do you overplant with Grass, or annuals, or nothing?  All these contribute to the fate of Irish bulbs.  RSVP and we can discuss even better what may have gone wrong here.