The problem I have with growing slips with the jar of water thing is that I can't get enough slips ready at once to do anything with. I need about 15 for the row.
This year I'm going to put a big trellis down the middle of that row and train the vines up and along it. That will release a lot of otherwise vine-covered square footage for growing something else... like watermelon or running squash that will cover it with vines.
