I would suggest that you plant a few different types of trees in a more random pattern than several of the same type tree in a formal row.

For example, assuming there is room for large trees and bushes, you could plant any combination tulip tree, bald cypress, dawn redwood, colorado blue spruce red maple, and then mix in your choices of bushy woody plants like forsythia, hazelnut, weigela, and smaller trees like american arborvitae, eastern redbud, dogwood, cryptomeria japonica, apple trees, whatever.

But if you just want a formal row, find the best cultivar of thuja green giant like everyone else does :-)

I generally don't like rows of the same type of tree since they are easily ruined by disease or if you lose one for any reason, it really messes up the row

A very common question on this board. Do a search to find the many discussions.

Dan

I'd suggest columnar European hornbeam, Carpinus betulus 'Fastigiata' (or preferrably 'Frans Fontaine', if you can find it - maintains a much narrower profile even into maturity). This is one tree that looks extremely handsome when planted as an allee or in a single species row and is remarkably trouble-free across the country.

FWIW, Thuja 'Green Giant' is NOT a columnar tree, although rather fast growing :-) Can develop a quite wide spread of 15-20' or more.

Rob, if your spot is anything but dry try to sneak in a Dawn Redwood or two. Open grown you can get a bit of a spread. Planted close together and they are as columnar as most normal trees.

These are about 100 foot tall from what I've read. Not very wide.

{{gwi:353686}}

My backyard abuts a main road. Several times in the last few years, cars drove into my fence causing major damage to it.
I asked the town to if I could install a guard rail, or place boulders in front of my fence for protection, they of course disallowed it, however, they suggested that I plant a row of trees to act as a natural guard rail. I need something fast growing that will grow to have a single straight thick trunk like Maple, Oak, Sycamore, etc, etc., but can be planted closely.
I would consider planting thuja Green Giants, or other conifer, but I believe that they would have several trunks. I don't care if they are deciduous or coniferous evergreens. I checked several nurseries for Hybrid Poplar, but none sell them. In fact one nurseryman told me what a disaster Poplars can be.

The reason I want to plant the trees is to act as a "natural guard rail"