I just layed mine horizontally a 1/2 to 1/4 inch below woodsy humus rich soil. They've increased significantly. When I see them in the woods the rhizome is almost on top of the soil.

Thanks!

I agree. They don't need to be planted very deep at all. If conditions are moist, just layering a little mulch over them (with the emerging leaf exposed) is probably sufficient. If there is a noticeable root 'below' the thick rhizome, I would make sure that it is buried into actual soil.

In the woods they naturally grow with those dried string nodes you described being under the leaf litter. The green fans grow upwards and the flowers bloom about this time of year (depending how far north or south you are).

They will send down roots into the soil. Those roots tend to be fragile. The rhizomes tend to grow horizontally right at the soil level. The rhizomes are the dried string nodes you described.

Here is a link that might be useful: Detailed info and photos for Iris cristata.