... and for those who are wondering why, I pot up iris.
I do it for several reasons, mainly because I still need to prepare garden space for them, and potting them gives me time until that's accomplished, BUT the following is the more important reason that I pot iris.
In my locale, a disease as damaging as Soft Rot occurs in the fall and winter months, called Botrytis convoluta, or Gray Mold. It leaves the rhizome an odorless pile of mush by spring. If I planted them directly in the ground I usually have significant losses by spring of the new plants. Suttons was attacked by this pathogen and lost a lot of their newly planted 2018 intro stock this year. If I had known Mike was going to be bedeviled by this disease I'd have contacted him and given him the tools to combat it..... but oh well :(
Planted in pots with a steam sterilized potting mix, I can have the plant develop a root system and become established before planting them in the row, so it resists being infected by botrytis at least in the short term.
To maintain long term control I have to spray the clumps with fungicide every 14 days during our cold, foggy and cloudy periods. These cold, damp, gray periods can last for weeks in the Columbia Basin some years, and this stagnant weather pattern offers an ideal opportunity for the pathogen to take hold.
Because our diurnal highs and lows are greater in the winter then, lets say, Portland or Seattle, this causes the rhizomes to "flex" ie expand and contract as the temps warm and cool down. This "flexing" due to wide temp changes, results in the rhizome developing miniscule cracks.
These cracks allow the pathogen to invade and set up shop, therefore eventually destroying the rhizome. Susceptibility varies from one variety to another and isn't color or color pattern class dependent, although there seems to be a small correlation of botrytis susceptibility and cultivars from milder region, like central, southern CA, and Australia.
This is more an example of a location dependent cultural tweak/defensive cultural procedure, rather than a empiric growing requirement
