Dividing large rhizomes

I have just noticed that the rhizomes of my middle height irises seem to grow differently than the TB's. They grow fans all the way around the center rhizome in a circle. Should I cut them off the center rhizome, or divide the big center rhizome in half (or quarters) with the outside fans still attached to the rhizome?

How large of a rhizome is needed to bloom next year? The more rhizome the more bloom, right? I am thinking that as long as there is no rot I should leave most of the old rhizome attached to the growing rhizome?

If I am seeing overcrowding and falling stalks due to rot in some clumps, should I just dig and divide them right away rather than wait till July or so?

Is there a book on irises that answers all of these type of questions that anyone can recommend?
Thank you,
Sharon

WOI (World of Iris), available from AIS for $25 US or so will answer everything. It is my iris Bible.
edited to add
You can also look on http://www.abe.com for a book by Molly Price. only $1 or so. Old but good.

inanda



This message was edited Jun 4, 2006 10:01 AM

Thanks, Inanda,
I didn't find it at amazon, but they had a different one from AIS. I suppose I will look up their website and see if it is for sale there...
Do you grow irises in zone 2b? Are there only certain ones that will grow there? Which ones are your best growers/favorites?
Sharon

I don't know that 32 page AIS boook but sure it will be fine.

Favourite iris - whatever is in bloom at the time. Am in love with siberians and Louisiana iris mainly. Have no luck with arils, probably because I don't look after them properly.

We grow most of the different types of iris up here. This year has been quite spectacular. TBs are now winding down and siberians are starting to bloom now.
inanda