Dividing Iris

I have a couple large clumps of Japanese and Siberian Iris' that have been expanding in the back of a bed for several years. They seem to be doing OK, but are getting out of hand. How often should they be divided ? Is there a size or every so many years ? Some knowledge on this issue would be appreciated. Thanks

Under good conditions Japanese and siberians should be divided every 3-4 years. If you see them dying out in the middle, or the middle of the clump has no leaves coming up they need division. Or if the bloom becomes less they need division. If they are blooming well, and not dying out in the center they are OK for another year. Siberians can often go a little longer depending on the cultivar.

Newest info says not to replant Japanese where Japanese have been planted before, but I have so far not found that to be the case. I amend the planting hole well with compost and composted manure and replant and have had no problems.

Replant divisions of at least 3-4 fans and keep well watered for the full growing season after dividing.

Hey Robert, I have no clue. But Carla does and she showed me some things. Now is the time to plant them, and divide them and replant. They are tough critters. Or wait till after they bloom next spring, If you wait till after they bloom next year, just dig them up take a look at them then find the mother and divide, They are soaking in all the nutriments now

Well that answers my questions quite nicely. Thank you for the help.

You're certainly welcome.

We love pictures of Japanese and sibs here, by the way. Maybe come back with some pictures in spring.

I'll do that pollyk, I like Iris but they so far have not been very predominant in my garden. I've seen some incredible specimens in the Plant File and am drawn to the blueish ones so I suppose it is inevitable they will somehow find their way into the garden.