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Re: CULT: Transplanting Irises

  • Subject: Re: CULT: Transplanting Irises
  • From: Paul Tyerman <ptyerman@ozemail.com.au>
  • Date: Fri, 01 Jun 2001 21:42:22 +1000

> The highest increase rate and the strongest growth plus bloom I have 
> ever seen has come from late May-early June division and reset--
> without the butch haircut.

There is a change taking place in the horticultural community regarding
root pruning and associated foliage pruning (not just irises, but
anything).  It was always said that if the roots were trimmed by 1/3 then
the foliage should be trimmed back by 1/3 to balance the loss of roots.

They're now finally realising that this isn't the way to work.  By trimming
the foliage as well as the roots you're giving two shocks to the plant from
which it has to recover.  Removal of the foliage removes feeding potential,
plus removel af roots does the same thing.  By removing both you're
affecting the plant that much more.

As far as I knwo the reason for trimming back the fan is to stop the newly
planted rhizome from toppling over.  This is generally the case in shipped
plants because it helps conserve space, plus the roots are removed so it
had no means to stabilise itself in the ground.  I have found that plants
are definitely happier i their root damage is minimised, and the foliage is
left intact.  If you lift hte rhizome carefully and replant with a good
splay of roots, covering them firmly, then there shouldn't be much in the
way of movement.

I was also told when I first started with irises that you must be extremely
careful with iris roots as they do not regrow if the root tip is broken
off.  I was told that they do no branch and they they would have to start
growing a new root to replace it.  If you have been told this it is a LOAD
OF CRAP!!!!!  I have tested this specifically to find out and if a root is
broken it will branch and more roots will emerge from the side of the
existing root.  I originally treated them with extreme care as I was afraid
of hurting them...... they will survive just fine on their own.

Basically, if you're lifting and dividing your own iris.... lift them with
as many roots as possible.  Replant them with the roots splayed out on
either side of the rhizome and firm the soil over them.  Don't mess with
the leaves as they allow for extra food to be produced, or alternatively if
the plant is suffering it will withdraw the nutrients from the leaf back
into itself.... so the leaves act as a sort of storage buffer.

I've always been told that the best time to divide irises is when they are
in flower (or just after) before they head into their growth cycle.  This
makes a lot of sense as it will minimise root damage as the new roots start
as the new side-shoots develop.

That's pretty much a summary of what I've been able to come up with.



Paul Tyerman
Canberra, Australia.  USDA equivalent - Zone 8

Growing.... Galanthus, Erythroniums, Fritillarias, Lilium, Aroids, Irises
plus just about anything else that doesn't move!!!!!


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