I'm in a suburb in southern Ontario. We decided to buy a house that backs
onto conservation to get a little more privacy than the standard lot would
offer. Everything was great until our next door neigbour decides to
install
a patio door and 2nd floor deck off the back of their house with a full
view
of our back yard!!! (which wouldn't be so bad if they had a better past
time
than watching us swim).

SNIP

Obviously a row of trees is in order here -- shrubs just won't cut the
mustard. I'm not familiar with the climate in Ontario and you do not go
into detail about the property or soil, so it's tough to make a
recommendation, but there are a number of fast growing trees that are also
cold hardy. Something to be aware of however -- fast growing trees are
typically not without their problems.

Russian Olive grows well but tends to become invasive (billions of berries
that the birdies love) and they get pretty ratty. Junipers are tired and
overused, Elders invite pests. Laurel is a nice option and it's evergreen
however it's also poisonous if ingested (bad for kids, bad for pets). Pea
Shrub suffers the same issue as other shrubs -- only get to around 15 feet,
quickly become ratty, difficult to maintain and not very attractive.
Buckthorn is nice but again, it's a shrub plus it's perennial.

Several of the species you noted are viewed as invasive and in some cases
downright noxious. Something else to consider is the impact what you plant
will have on your pool -- you don't want anything that will over shade the
pool area or it will always be chilly when going for a dip. Just
something to think about.

Someone recently suggested Royal Paulownia (Paulownia Tomentosa) to me as a
viable option for some trees of interest and I'll be looking at those here
soon. Some folks hate 'em for their seeds and/or invasive nature while
others love them -- pretty standard response there.

Local ordinance requires that a fence be not more than 6' tall. Does this
apply to privacy fences or open fences? If only the former, then install
what amounts to a 10' lattice fence and cover it with vines.

If a fence is a fence is a fence by local codes (not always the case mind
you) then look at how you can actually combine solutions to achieve the
desired effects. For example....

1) Build a 15' tall pergola that separates your property from your
neighbors' property. Make it's width about the same as your pool (i.e., the
area to be blocked). Add various vines such as wisteria, clematis, and
honeysuckle to the pergola to cover it and make it an attractive landscape
addition. (As an added plus, this gives you a small sitting area.)

2) On either side of the pergola, add a 6' tall fence, per code. Tie it
into the pergola by giving them a common wall (i.e., the back of the pergola
matches the rest of the fencing or all are made from the same material, and
so forth). This adds privacy all the way across.

3) Plant a series of trees along the privacy fence area that will grow and
shield the remaining area from view. This further lends interest to your
landscape. Some species grow very wide -- might be your best bet.

The bonus about this design is that it not only gives you immediate privacy
but can really enhance the property. By rights, even your neighbors can
enjoy it if this is done properly -- there will be a nice privacy fence to
keep their side private, plus the pergola will have several beautiful
flowers and wonderful fragrances for them to enjoy while sipping tea on
their deck.

Oh well -- enough rambling. It's 2am and I gotta get some sleep. :P Hope
this helps some!

James