I'm in zone 5, as well, and I always plant my tubers 3-4 inches under instead of the recommended six inches so my tubers have warmer soil in the spring to get a good start in. This has worked fine for me.

I bury tubers with small sprouts in a reverse cone of soil, allowing the sprout to 'breath," being sure the neck and head are covered to protect from roving insects. I reserve a pile of dirt & mulch next to the sprout hole, and fill it in as the plant grows.

Thanks for the response,CC. I've planted some as you have described but wasn't sure how to plant this one since the leaves extended down to almost touch the sprout end of the tuber. I'll only have a half inch of soil covering that end until it gets taller. I've had to build "mini-dams" around the shallower planted ones since our recent inches-per-hour rains have created miniature swimming pools. A few tubers have rotted, naturally my favorite ones. I have had to dig up some and replant after the soil dried a little. I don't think the tubers like being disturbed. lol

Better disturbed then rotted and gone! I've reactivated my grow lights, and am resuscitating some... stubborn... tubers that have started to rot or just aren't doing anything. I am amazed to see Woodland Meranda recuperating from surgery up to the neck! Three sprouts, with two destined for cuttings in a week... This is why I like to plant in pairs, but sometimes you only get one...

I'm impatient... I've got reserves for those holes, if those silly tubers given the chance don't shape up! (At least that's what I whisper to them when hubby can't overhear me! My addiction has to show restraint around the 'but its just a flower' crowd!)