Spent the day getting my new grape cuttings on the heat mat. As soon as they arrive, I start them soaking to rehydrate the wood. Juicy wood supports good callus which is what forms the new roots. This morning I mixed up perlite with a bit of peat potting mix then dipped the cuttings into rooting hormone and stuck them in the two inch pots. Then they all went on a heat mat at 85 degrees.
I've tried a slightly different method on each batch of cuttings, and I think either I'm getting better, or the refinements in the techniques are helping. I used all my six inch pots on the osage oranges, so I'm using a shorter pot, but it should heat better. In a week, I'll start checking the bottoms of the grapes for callus, and when it forms, I'll move the cuttings into gallon pots to finish developing roots.
I could plant the callused cutting directly into a prepared bed, and I've done that in the past, but our soil is so cool (and so hard, and so alkaline, and so many critters are out there) that I think the grape gets a better start growing out in loose potting mix.
My favorite reference for grapes is The Grape Grower--A Guide to Organic Viticulture, by Lon Rombough, which I heartily endorse--it's clear, and truly comprehensive. I have always ordered my cuttings from Mr. Rombough. Sadly, he passed away last winter, but his family was able to supply my grapes.