On Feb 5, 10:48*am, mike wrote:
On Feb 5, 8:58*am, gardengal wrote:

On Feb 4, 11:59*am, mike wrote:

edit: *I might even try 2 foot *spacing on center.

I might rethink that :-) 'Green Giants' are hybrids and only
tangentially related to standard arborvitae (Thuja occidentalis).
Their typical spread is more closely related to Thuja plicata (one of
the parents) and can reach 25' - they are not by habit columnar and
narrow in profile, but rather more of a 'Christmas tree' shape - more
or less conical and broad at the bottom and with a tapering tip. Too
close a spacing will result in heavy shading and die out of lateral
branching and you could end up with a very spotty looking privacy
screen. Recommended spacing for a dense screen is 5-6' o.c.,
otherwise, 10-12'.



I understand, but don't all hedges have lateral branch die-off due to
adjacent neighbor shading?

Not necessarily - hedges are contructed from a variety of plants, some
of which are far more suited to this procedure than others.


Also, from what I've read, they can be trimmed to any shape (i.e.
rectangular) even if they would tend to be a tall cone if left alone.

If you are willing to put forth the effort to keep them trimmed/
sheared and within bounds, yes. The issue is that Green Giants are
very fast growing (3-5' per year) trees that grow to a pretty
substantial size - 50-60' with a 25' spread. That's one heck of a lot
of trimming....like at least 3 times a year.

Many selections of common arborvitae - Thuja occidentalis - are very
narrow and columnar in form and make much better hedging candidates.
One of the most popular and widely used is 'Smaragd', aka Emerald
Green. This can be spaced quite closely, only gets to be about three
feet wide and 15' tall. And these plants generally produce multiple
leaders, so topping or leveling off the tops at a specific height is
very appropriate. Green Giants typically produce a single leader, so
topping is much more of an issue, causes health issues for the plants
and generally results in a rather short life span.

As to "parroting" back spacing recommendations, as a landscape
professional, these are plants I've grown and worked with on a number
of landscape projects, so I am pretty darn familiar with them, their
growth habits and the habits of both the parent species. And spacing
recommendations one finds from nurseries and growers, extension fact
sheets, even books are usually provided for good reason. These trees
are far more similar to Leyland cypress than they are to common
arborviate - big, very fast growing trees. 'Screening' is also quite
different from 'hedging' - screening implies allowing the tree to
growth to its natural form and size with minimal pruning. Hedging
refers to maintaining the plants in a formalized shape and at a
specified hight and reguires frequent and ongoing maintenance. Both
Green Giants and Leylands are good screening plants but not very good
hedging plants, simply by virtue of their growth rate, habit and size.

But you've apparently made up your mind despite the advice
given......which by the way, you ASKED for. If you don't like it,
ignore it. Go ahead and spend the money and effort, space as you wish
and be prepared to be busy with the ladder and electric pruning
shears. And plan on replacing your 'hedge' in 10 years, probably less.