To root grape cuttings:
1. Soak them in a jar of water for at least an hour so they are very turgid.
2. Create a good loose medium- could be sandy soil, but I like to use peat moss, perlite and sand.
3. Fill pots that are at least the same height as the cuttings and water well.
4. press cuttings in so that only the top bud peeks above the soil line.
Now, the golden standard is to have the pots in a cool room (cellar, barn, etc) and do the following and create a little bottom heat. I use a heat mat, but I used to simply take a shop light with a low watt incandescent bulb and place it below the pot. The pot can be set on a grate, cookie sheet, etc that will transfer the warmth. Clay pots are better, but plastic will work as long as the bulb doesn’t get too close to melt it. A cool top and a warm bottom really speeds up callusing and rooting.
Do you need to do the above method? No, but, it almost guarantees success. Whatever method, I always put one or two in a clear plastic cup, with the cutting against the side so I can view its progress.
If you use larger pots, you can just leave them there this year and transplant to their permanent location in the fall or next spring. If you transplant this spring, you want to time it so that you do so when a callus has formed, but no roots or stubby little ones, as the longer ones almost always break off in the transfer.
callus- this is a white proliferation of undifferentiated cells that form at the wound site at the bottom of the cutting. Roots may form in it, or a bit above.
make sure only the top bud peeks out of the soil, do not leave a long piece in the air, as it will likely dry out and kill the top bud, which is where it will grow from.
The callusing should happen by about 14 days.