Deer can be expected to browse Thuja occidentalis from their head level to the ground, producing a dumb looking effect. Supposedly yew is also quite on the menu although I don't see it being hit noticeably around here - but such things do vary regionally.

If the cypress next door is not showing disease or pest problems maybe just plant some more in the gap, shear as needed to control size - it produces an excellent close surface when kept barbered.

It occurred to me that the only portion of this planting that I will view regularly is what grows above the fence, so some deer browse in the lower portions won't be to much of a concern. A lot of wind comes through this portion of the yard from the bay, and my neighbor has had issues with her leylands tipping, so I'd be hesitant to plant more of them, although keeping them at a shorter height may mitigate the issue. Are green giants a variety of Thuja occidentalis? I thought a hybrid of some sort and perhaps less attractive to deer?

Ken, I will try to take pictures tomorrow showing more of the layout. These would be planted on town property, which brings up a good point, width is an issue. I'd rather not have something growing outwards into the street.

My neighbor and I have very deep yards, and she has planted this hedge all along the backyard portion of our shared property line. I was not happy when I learned of her plans, but there was not much I could do. I keep it sheared at the property line, which isn't as much work as you'd think, since I suspect it grows more towards her sunnier side and upwards. Those green posts you see support some wire fencing to keep the deer out. Now that privacy is also an issue, we plan to install the stockade fence. Yes, that would be at about the same height, but since my yard slopes downwards, from a higher vantage point, you would easily see over fence into the lot beyond.

Are there any Thuja that grow slower than Green Giants, but also fast enough to create the desired effect in the not too distant future? Or other tree types entirely? As I mentioned, I'm more concerned with what's above the 6' mark, so a pine tree or something similar could also work.

I appreciate the brainstorming!

-Chris

Dimensions of 12 x 15 sounds like a shrub. Just food for thought. In your zone 7 you have lots more options than I’m familiar with, but I would consider broad leaved evergreen shrubs as well.

Hollies or other various broad leaved evergreens would be better for this purpose.

This is the same view but pulled back. You can see my neighbor's Leyland hedge along the left. And our chicken house and veggie garden. It puts the gap I'd like to fill in better perspective.

A holly or other kind of large shrub would be great. Any particular species or cultivars I should consider?

In my opinion on LI zone 7 you should grow one of the showier Eurasian hollies like the Highclere: https://www.houzz.com/discussions/6053297/some-midwinter-pics or Koehne; or perhaps more readily obtainable and smaller, one of the various meserve hollies like 'Honey Maid' which seems to be marketed in the northeast: https://www.pridescorner.com/plant-name/Ilex-X-Honey-Maid-Holly

You should be prepared to prune young hollies thoughtfully for a few years to make sure they take on the optimal form: https://www.houzz.com/discussions/4977109/we-agree-some-cutting-grown-trees-need-aggressive-waterspout-control

Hollies are more expensive than conifers for screening, but are a better long term investment in my opinion because their size can truly be controlled in the long term, and you can even "start over" by cutting them to their trunks if that became necessary for some reason. Other than driving to McLean Nursery in Baltimore I don't really know where to tell you to buy more upscale BLE plant material like such hollies, other than Hicks nursery which once had a reputation as the best on LI for that sort of thing. Looks like this poster found some at HD: https://www.houzz.com/discussions/5145600/broadleaf-flowering-evergreens-for-casual-hedge (see last post; whole thread might be informative for you)

Also in fairness legacy plants like Hollies (and other BLEs) are forever plants. They are slower growing than 'conifer screens'. If I were planning to flip this house in a few years, just put in whatever junk some teenager at HD or Lowes tells you to buy LOL. 99.999% of buyers won't care about the difference. (maybe 99.997% on Long Island haha. It is a slightly more horticulturally active part of the country.) At least use a better one like 'Green Giant' or a Cryptomeria. But the fact you're actually asking here implies you maybe wanted better advice.

This could even be a job for something like Magnolia 'Kay Parris' that you could probably find in a large size, somewhere in the NYC area. For a price ;-)

How about one of the evergreen viburnums?

Yes those can be good too but I think, as a group, they are a little behind the hollies in reliably sizing up to form a dense screen. Would be interested to see if NOVA Dave agrees with me. Still I do collect them when something catches my eye. I have tried and failed with the somewhat legendary "Laurustinus". Just a little too cold in the colder winters here. I keep meaning to plant a 'Dawn' but never get around to it. McLean Nurseries focuses on hollies - surely the biggest selection in the country these days, since they've become plantae non grata in the PNW - but once in a while he has something else bordering on super rare. Last time I was there I bought a Viburnum henryi - a plant I've almost never seen for sale even mail order. Will be growing it next to my 'James G. Esson' and assessing it! There are probably other thread on here about best choices for hedging in the coastal northeast. The Prague Viburnum comes to mind as being known for hardiness.

English holly is the weedy species here and not any of the others. Yet still remains prevalent in the occupied landscape. With independent outlets here stocking a variety of other kinds. And even a small assortment of English holly cultivars.

Some great suggestions. Thanks all. I guess it will come down to what I can find locally.

And what you like the look of when you find it.