I know there is much discussion and varied opinions regarding how many hours to have seedlings and cuttings under grow lights before planting out. There may very well be other drawbacks to my light to dark ratio, but I have always had my grow lights set for 12 hours on and 12 off. If the cuttings have been around and rooted for a bit before I plant them out, they always have small tubers already forming that I can feel as I pull them out of their trays to plant. The only time I have gotten roots only from cuttings were ones that other people made. I have always gotten at least a small tuber clump from every cutting, with leaf node cuttings producing the smallest clumps.
Is it my light ratio while the cuttings are rooting? Is it magic and happenstance? Not sure. Since I always get tubers, I'll just keep doing what I do.
I have experienced that burying more nodes, whether it be by planting more deeply or by covering a stalk definitely works and those tubers are perfect with easy to find eyes. Usually 3 tubers per node. Heck - tubers will form even if the stalks are merely laying on the ground and not buried. I discovered this when a windstorm nearly took out my pompon patch. I didn't have them planted tightly enough to hold each other up with the corral method and several stalks of several cultivars just lay on the ground from August 'til frost and all of them had nice tubers on the stalks!
