Re: Cult: Elongated Rhizomes

>  >. In some cases these rhizomes can get a foot or more long
>>  with no bloom and no increase and then for reasons unknown to me they will
>>  make six to eight increases on each side of the rhizome. There is so much
>>  we do not understand about the growth of tall bearded irises! Fred Kerr
>  > Rainbow Acres Near Sacramento, CA

If a rhizome doesn't bloom, it grows vegetatively for another year. 
Check those elongated rhizomes and you will see a constriction or 
narrow place that marks the end of each year's growth without bloom. 
When the last section gets large enough, it will bloom and the 
rhizome will branch normally.  However, if the rhizome gets long 
enough, the inhibitory hormone produced by the terminal bud will 
become too dilute to work by the time it reaches the "back" of the 
long rhizome.  The lateral buds will be released from inhibition and 
begin to grow.  I have found that long rhizomes are most often the 
result of overcrowding, poor soil, or not enough light, causing the 
rhizome to fail to accumulate enough reserve to bloom.

If you move such plants to better conditions, it's just as well to 
break or cut the rhizome at the most recent constriction (the one 
closest to the fan).  The additional length of rhizome seems not to 
do any good and could be a source of rot.  If the variety is a 
valuable one, bury the leafless section in good soil and it should 
produce several new increases.

A lot about iris growth can be understood if we remember that the 
rhizome is a stem, and behaves accordingly!
-- 

Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<wshear@email.hsc.edu>
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