I agree with Wayne, a healthy Arborvitae hedge makes for a very good tall narrow dense screen. One can often obtain large specimens at a very good price, just be sure to get those that are well rooted in pots or have large burlaped root balls. Some places offer freshly dug specimens with severely amputated roots that are crammed into tiny pots, avoid those! I also like some of the upright junipers, though they are prone to thinning out if not exposed to long hours of sunshine, also junipers will be much higher priced than Arborvitae.

Unfortunately, Swedish aspen and many aspen species are doomed due to Bronze Leaf disease. The disease is now just making its way into my area and I'm seeing many formerly healthy Swedish aspen in severe decline. We might also have a major ecological disaster on our hands if our forests, which are brimming with trembling aspen do become severely affected.

We've had bronze leaf for years in Calgary. Doesn't seem to do much actually. The native aspens are highly resistant.

I'm seeing the first signs of infection upon many of the trembling aspen that surround my property, I guess time will tell to what extent the disease harms these trees.

They seem to shrug it off. We have many native trembling aspens in the neighbourhood as well and they will get it in a branch... and that's about it. The city marked the trees for further examination. This year there's been nothing.

SCAs however do get it much worse.

Took three years for mine to die....good luck!

I'm all surrounded by trembling aspen forest and it provides important protection from winds, so I'm very happy to hear that this species seems to shrug off bronze leaf disease. I have no Swedish or Tower poplars.

I'd go with spruce trees...[more reliable].. planted hundreds for wind brake, also into the bush and getting rid of messy short lived aspen....at least the ones growing near my veggies and fruit trees, aspen have unbelievable long root systems and have suckers come up miles away..taking moisture and nutrient.

Aspen and willows should be banned for home gardens in town.

Twros suggestion of junipers would be the most reliable tree, Mockorange is a native plant not that far away.

How are people on birch? I am wondering if the new stran of Dakota Pinnacle might be happy in the wet corner.

They would do well with the ground water, I just didn't think of them blocking out a view which they will do but will be sparse in winter.

Yes, spruce would also be a good choice, especially the upright narrow types, Canadian Tire often has pretty decent prices on those, though not so sure how they would handle that wet corner.

'Parkland Pillar' birch appears to be a nice one, though you're not gonna get the advantage of an evergreen screen.