James Scott wrote:
What is the best time of year to split a large bed of irises in zone 5

Northhawke


In any zone:

For bulb iris (sometimes called "Dutch" iris), divide when the foliage
dies.

For rhizome iris (e.g., bearded iris), check with a LOCAL nursery and
ask them when they will have bearded iris for sale as bare root
rhizomes. (This must be a "real" nursery, not a lumber yard or hardware
store -- not Home Depot.) Go back at that time to verify they really
are available. That's the time to divide them. Work on one clump at a
time, replanting the same day they are dug.

See my http://www.rossde.com/garden/garden_divide_iris.html.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening pages at http://www.rossde.com/garden/