shaping grape vines
I bought a perlette green grape bare root this winter and it has sprouted 6 strong healthy stems in all directions (left, right, up). I want to achieve the same form as in this picture. Is it okay to cut off all the side stems and stake only one up or should I just stake it and allow all of the other stems to grow as well? I'm reluctant to cut them because they are so healthy. When is the best season to do this?