Cant really comment on varieties in your zone cause Im in zone 9. I grow Quinalt, All Star, Sequoia and Ozark Beauty here with okay results. For bigger berries space 12 inches apart so 16 plants should fit into 4x4 box. Any closer than 12 inches they start to compete for food and that results in smaller fruit. I removed the flowers and runners off of mine the first year but most people here try to plant in Nov or so and pull up the plants after harvest in the spring. It kinda sucks devoting a bed to them year round for 2 weeks of berries. Im going to pull mine this spring and make way for tomatoes and squash.

s, It all depends on your soil wetting pattern. Try 18" emitter spacing with two t-tape lines. If the wetting pattern is not reaching the whole plot add more lines and stagger the 18" emitter spacing. Trial and error is a good thing. aloha

Kerry, Valiant grape normally should be hardy in your zone, but I guess the problem is because it's growing in a pot above ground, the roots might get too cold. I have a few plants in similar situations and for winter I just dig a hole in the garden or a flower bed, sink the pot in the ground up to the rim (hopefully it's not too heavy to handle) and then fill in around the pot with loose soil, trying to leave no air pockets. If the vine is growing up a trellis you might have to carefully take down first. It might not hurt to mulch with leaves or straw and then when it snows to mound snow over that as well. This will be my first winter with my valiant grape. Mine is growing in the ground so I may just remove from the trellis and lay on the ground, so it can benefit from snowcover. Glen

I will be planting some here in NJ in another week. They transplant best when daytime temperatures are in the 60's here. They will survive a light frost if not blossoming.