By Bernard
Cambridgeshire,
United Kingdom 
I'm currently struggling to break up a large clump of irises that I believe have been growing in the same place for about 25 years and the clump is virtually a solid lump of virtual concrete. My aim is to separate individual plants and replant about 3" apart to form a new clump having dug the area over and incorporated plenty of compost. . A point of interest is that the flowers are the usual colour and quite small but rather than the rhizome which my other irises have, these plants have what appear to be small bulbs at their base and presumably need to be planted normally.
Does the small flower size and the root type give any clue to their identity?
The main thing I wanted to check with you is whether it would be a good idea to cut the leaves down to a feww inches to relieve the load on the roots while they establish themselves?
16 Sep, 2011
Answers
My theory is the clumps were not split into small enough divisions, when i split sibirica clump into small divisions of what looked like 4-6 plants they flowered the following year.
16 Sep, 2011
Why not try soaking the irises really well first - you may find this easier.
16 Sep, 2011
Fingers crossed, I separated them out into individual plants - just have to wait and see. Does nobody have any thoughts on the shortening leaves idea?
17 Sep, 2011
Your irises may be a Siberica variety. I split a large clump - with great difficulty- three summers ago and the bad news is, that although I thought this would help them to have more space, they did not flower at all the following year and only flowered a little bit this year. Another member on this site (Bulbaholic) reported the same problem. I hope this does not happen with yours. Perhaps it was just the particular varieties we had.
16 Sep, 2011