That depends in part on the height they can grow to, and the varieties. Common wisdom on here and other sites has different varieties set about 5 feet apart, and plants of the same variety about 3 feet apart. That assumes they are growing up lines to a trellis or something like that which lets them grow to 16-18 feet or so. Most folks rig up some sort of poles with lines attached, tall trellis, or so on. If they are growing on a 6 foot wood or chain link fence, then the horizontal spread will be much greater, so the number of plants must be less. The one I've seen on an arbor by a fence probably has at least 8 feet in width of the crown, maybe more. Mine are growing up lines to the railing of the deck, 1&1/2 stories up, and the lines are angled out to add some length, and to spread them out in the sun.