Loic, I'm hesitant to say this (again) because it annoys some to hear
it, but I have problems with the big robust (sappy) rhizomes that many
others seem to like. They don't adapt to my growing conditions well at
all. I bought a batch like that last year, and I think all but one of
them died - more susceptible to freeze/thaw/rot damage over the winter.
The only blooms they produced were on small increases, most of which
did not survive past bloom season. If I buy from that grower again (and
I may, just as an experiment), I may store them indoors in cool place in
a paper bag until the following March after the worst of our freezes
(usually), then pot them up outdoors.
One CA grower who used to send sappy rhizomes has quit watering in the
summer (at least the ones I get) and they seem to survive here <much>
better than previously.
>From the photos you posted, it does look like the smaller rhizomes had
a bit too much moisture or too little air circulation for the length of
time they had to be closed up for shipping. But I wouldn't object to
the size for my growing conditions, as long as that is blooming size.
My two cents.
east TN USA zone 7
wondering if it's suddenly going to go from months of 95oF to 20oF any
day now...no rebloom other than IMM & Belvi Q, & they are done for now.