[Alice]

We have Iris germanica growing at the drip line of olive trees and Quercus ilex. The sources I have consulted say that the rhizomes should be lifted every 3-4 years and divided, otherwise flowering will be reduced. I don't really want to disturb the tree roots too much. Any advice?

[david glen]

Don't worry. Irises resist bombs and hatchets. Wait until you see the place gets a bit  crowded. Mine's roots  are quite visible and I can see when they need to be moved.

If yours are too crowded , then dig some of them up,  chop the rhyzomes vertically into their anatomically separate pieces ( an egg slicer is not the idea  here !) and transplant around  the same place and further afield . Finally you'll be throwing them away. They are the only plant that I don't care for in any way and they grow anywhere dry and neglected.

Start now before the rains. 

[Alice]

Thank you, David.
It was more the tree roots I was worried about but it is good to know that I can be quite ruthless with the Iris rhizomes.
I wonder if yours grow so well because you dislike them..?!
(Actually, it occurred to me that perhaps I misunderstood your "I don't care for" and that you meant instead that you don't give much attention to them.)

[david glen]

Alice

You see how misunderstandings can cause a war?  I meant to say that I don't mollycoddle them. 

My irises were lifted from very shallow soil . They shouldn't affect your trees' roots. In fact I tore mine up by hand in summer, so there was barely any disturbance to what's below.

They are very tough  but I suppose they are best manhandled when dormant, so start movin¡g them now.

David

[Alice]

Thanks David, I will.
We just got to Paros yesterday and everything is bone dry.