Questions on Arum italicum

[Jaeda]

I've got seeds for this (couldn't resist - the Jack-in-the-pulpit-like form just hooked me) and from what I gather cold stratification and/or GA-3 can be of use in urging germination. I know that they can take up to a year or more to germinate. I know they shouldn't be disturbed for at least their first year of growth. I know that the recommended temperature for getting them to germinate is 15°c/59°F. But what I don't know is:

How much depth from the first 1-2 years of sowing (from sowing, say a year to germinate and a year to grow undisturbed) is needed for them? I don't know whether (because of other things in the works where these are to be placed outside) to go ahead with the container I have in mind for them, or if I need to get or make containment that is deeper than what I have on hand. So I need to know a minimum container-depth for the root systems. Does anyone know???

The plan - as it stands now - is to sow them in a windowsill-type pot/box and submerge that planter into the ground to rim level - because where I want to start them at may have to be trenched through during the "do not disturb time" in order to run new electrical wire underground (we're planning on moving our electricity meter out to the front of the property either near the perimeter fence on the inside or possibly just on the other side of the fence in order to insure that the turn-over of different meter-readers doesn't cause an issue because some of them aren't dog-friendly or dog-nice even if the 9-canine pack running here are the most loving creatures in the world [8 Rottweilers and 1 wolfdog look intimidating to an untrained eye]) AND the raised bed where I want the Arum italicum is destined to be trenched right down the center length-wise for the underground wire to connect to the existing connection right at that end of the house. Hence - I want to be able to provide the right location for these seeds-cum-plants, but I need to go the route of a container in order to insure that the roots/corms/seeds won't be disturbed if we tackle that project during that timeframe when they shouldn't be messed with in the soil.

But I can't find any info about root depth for this species! I don't want to stunt them with a container that is too shallow.

Help?

Jaeda