How close is too close when spacing privacy trees (green giant arborvitae) and what do I risk?

[JayArbor]

I planted 30 trees in October. 8 feet on center and 5 feet between rows. This left 6.5 foot diagonals. The effective head on spacing looks like every 4 feet.



The pictures are at bad angles to see the spacing but the goal was a compromise to get faster screening and be healthy into maturity. But I really thought 40 foot maturity... now I'm reading more about 50-60. I am in NY so I imagine the shorter seasons might limit the future height? They do get basically full sun outside of sunrise and sunset. This row runs E->W. It is windy to the north so not sure if that could further limit the growth?

I do need a tall SCREEN. Ideally grown together up to 25 feet so can block neighbor's house on a hill (deck and windows) that is 35+ to roof.

At 40 feet, I felt confident I could prune them narrow over the years so they were 20-25% width to height. So that's 8-10 feet of width and gives me a screen without too much crowding.

At 50-60 feet though... that's another 20 feet and they will need to be wider and could crowd.

What is the risk at that point?

Should I consider transplanting this fall? Or is a few more feet not worth the shock if they are doing well? I would likely move to 10 feet on center (maybe 12) but they'd gain only 1 or 2 feet diagonal and 2 or 4 feet between rows. Does that even make a difference? I guess you have to draw the line somewhere on what's too crowded.

What are the downsides I'm facing if I'm too close? And do you think I did plant them too close?

Of course the fact that I might not even live to see them at 60 feet (I'm in my mid 30s) should be a consideration. But want to leave the trees to serve the future generations!

What do you guys think?

 

[TNTreeHugger]

I think I'm totally confused about what your wanting to do...but you want a privacy screen at least 35' in height to block your neighbors house?
I have a row of Green Giants, planted very small, about 1' and spaced, idk, maybe 8' on center. While the lower part of the trees are touching, there are gaps between them at the top.
I think you should have gone with Emerald Green or Dark Green arbs and planted them closer together. Those are a columnar shape. The Green Giant is more like a Christmas tree shape, and thicker at the bottom.
These are about eight years old...

These are some emeralds I planted about five years ago, now they are taller than the porch roof and have grown together nicely to form a wind block.

 

[CR888]

When planting screen trees I think about how big they will be when close too or fully grown. So you need to know what their size will be at maturity.

 

[TNTreeHugger]

A cedar might be a better choice for what you want...
https://www.mortonarb.org/trees-plants/tree-plant-descriptions/eastern-red-cedar

 

[BC WetCoast]

We plant arborvitaes root ball to root ball to give instant screen.
A 40' tree to prune to shape is tough if you don't have bucket truck access. You can get 20' orchard ladders, but standing at the top of one is sketchy to say the least. Then trying to reach 20' above that with a pole pruner, sounds easy but isn't.
Do you really need a 35' screen? You might be better off getting deciduous trees that are leafy in the summer, underplanting some cedars to get the low screen. The trees would lose their leaves in the winter, but do you need the screen when you are primarily indoors?