Grape Vines aren’t planted from seeds, they are planted from the shoots of other grapevines or better known as propagating grape vines.
Therefore, if you want to make a grapevine from scratch you need to show up to a vineyard when they are pruning. Depending on where you are located wineries will do pruning at different times. In northern climates, we typically don’t do our first pruning until after the cold snap. March or later is safe here. This is when a winery is cutting off 90% of the growth from the year before and this is the time to get your free grape vines. Wineries generally don’t object to people taking their cuttings and it is a very common request. Just ask and most will be happy to give them to you.
Take the following in consideration when looking for cuttings:
Disclaimer: I would only recommend using propagating as a technique for learning how grape vines grow. You will get a much higher success rate in the vineyard if you buy bare-root dormant grape vines from a nursery. They are experts in the mater and you are sure to have a nice healthy starting point for a grape vine.