We trellis one sweet potato vine every year because that is the one we pluck leaves from for greens. The others we let grow as they will and bury a node about every three nodes.
Once that buried node puts out
roots, I cut it free of the parent, this sets the new plant into tuber mode so we get more sweet potatoes at harvest time (for us that is November).
Through experimentation I found that this method works far better than leaving a vine whole and just covering nodes with soil.
Once you cut the newly rooting plant from the parent vine, the parent vine doesn't give up tuber making energy to the newly rooted part you snipped free. You have created two slips from one using this method.
I have a buddy that lives in Australia and he grows sweets all year long. By using the root a vine node and cut it free, he got normal tuber growth from all his vines two years ago.
Prior to that he would just bury a node here and there but he would only get a couple of good sized sweets per buried node. Now he gets 5-6 extra large sweets per buried node using this method.
He and I did the experiment at the same time of year and we both got near equal results so we have switched to the new method of cutting the new rooted vine free from the parent.
We grow our initial plants in tubs because of a vole problem. As the vines grow I leave about two feet of parent vine before I bury any nodes for new plant generation.
In last years season I managed to create 5 new plants per vine, and we still have some sweet potatoes to eat.
Redhawk