Maybe you can get yews to grow there, in your climate area. If not then probably Thuja occidentalis.

These - and all other possible planting options - will, of course take years to develop. Nothing you plant will offer the immediacy of a completed fence installation.

General notes...you'll need to be prepared to provide supplemental water for a couple of years, if not more. This could be an installed irrigation system, or a hose and a sprinkler, or anything else.

How tall are you seeking? How problematic are deer? How patient are you?

Cephalotaxus is a possibility. As are a range of holly...thinking in particular the shrubby meserve hybrids and similar. Boxwood, thinking dee runk, green tower, something like that. Rhoddies are a possibilty.

Yews and arbs are the classic such plants.

Manhattan euonymus is perhaps the best broadleaf evergreen screen I've seen locally...which is somewhere on the border of 5b/6a, albeit coastal (somewhat).

Box blight is now present and spreading in North America.

How tall are you seeking? 10-15ft at the most

How problematic are deer? No problem with deers

How patient are you? Not very much lol

I'm also rethinkng about swapping and just placing the shrubs in between the forsythias as I think it would be too difficult to try and remove them (plus I like them). This is not a huge problem and I can live with it as is but it would be really nice to have some evergreens back there since trees and shrubs are leafless for half the year and I don't particularly fancy see the moving company's crap for that amount of time.

Have you seen what your forsythia look like when bare yet? If they are large and full they may be dense enough to provide a fairly good screen. Not as beautiful as a green screen, perhaps, but functional.

Yes I have that's why I want some evergreens back there.

A thick forsythia hedge is impenetrable, summer or winter. It takes up space, six feet or so, but so is anything else. However, that looks like a pathetic excuse for a thin strip of plants. Which brings up the question of what is going on with the forsythia, and will a different plant do better. They look like they have been kept cut back fairly hard. If you are doing that - stop it. If the neighbors have been doing it, then figure out what you can plant on your side that has nothing to do with the forsythia. Plan on giving it space to grow.

Maybe it's not clear from the pictures, but the forsythias are NOT thick nor have they been cut back by me or the neighbour.

If anyone can suggest some evergreens that do well in the shade, I would greatly appreciate it. They needn't grow fast or high (max 10-15ft is preferred). If such a plant does not exist, please also let me know.

To my eye, the current forsythia look stressed from lack of water based on the limp leaves. As Embo said at the beginning, any replacement will take years to make an effective screen, and as Mad_Gallica said, forsythia, even without leaves, when well grown do make an effective screen. I have forsythia that completely hides what is behind it even in winter. Your back neighbor is pruning since the cut stems are visible in the last photo.

You have good sized trees (you mention maple on another post) competing for water and light with the forsythia, and any replacement will also have that competition, slowing the development of their screening ability. Maples are notoriously difficult to establish other plants near since they have many surface roots.

I would start by mulching the forsythia well and putting a soaker hose back there and using it for a couple of seasons to see if you can get the forsythia to grow in more thickly since I think that is likely to be the biggest bang for the buck and the time involved. I honestly can't think of another plant that will grow as thickly in that much shade. Hemlock and yew are the two evergreen shrubs that will grow relatively well in shade, and yew is both deer candy (mine was about the only plant bothered by deer, and they stripped it to the branches year round) and slow growing IME. Hemlock (Tsuga canadensis) currently has an insect that is killing it, so I wouldn't suggest planting them, and they will end up as large trees that eventually will need to be removed which will be expensive. IME other evergreens grown in shade will be scraggly, including arborvitae. Broadleaved evergreens such as rhododendrons and Mountain Laurel/Kalmia need organic-rich, acid soil, and to the best of my knowledge, much of Ontario has near-neutral, clay soil. If your soil fits the organic and acid requirement and you are willing/able to water as needed, one of the broadleaved evergreens might work.

However, I believe that better care for your current shrubs will be more successful than replacement. Perhaps you can get the back neighbor to stop pruning to allow them to be thicker? They are most likely trying to keep weeds from growing underneath, but if you offer labor to spread a thick layer of mulch under the shrubs and an annual weeding or two, they might be willing to let them grow wider.

swapping???

it doesnt have to be one or the other immediately ....

you can plant some backbones ... and leaves these here while they grow up ... and then eventually remove them ...

not many things die in shade .. short of dark grotto shade ... BUT ... the reduced direct sun.. can impact vigor ... as in how fast they grow to height .. how it all works in your spot is left to you going for it ...

soooo ... dont clean it all out.. and have some instant gratification regrets.. when it take 5 to 10 years to fill back in ...

ergo ... do it in stages ...

your F look like mine in drought.. you must have had a rough summer like we did.. east of detroit ...

ken

Yes, nothing new is going to be dense and thriving where the existing planting is thin due to tough site conditions.

Thanks Smivies -happy to get input from someone in Ontario who knows how Forsythia grow here and agrees that they are not dense. Looking out my window right now, I can see the stuff in my neighbour's backyard. Thanks for other suggestions too.

This part of the backyard has been completely neglected by previous owners - in fact some of them dumped garbage like it was landfill! I've cleaned up the area on both sides of the fence now I"m trying to figure out what do with land on the other side of the fence (previous owner put up chain link fence almost 10 feet from property line argh!). There are a lot of dead trees - I think only the maple is alive but it's too costly to remove them (I already had to get 5 of them taken down). I should also mention that I don't water that part of the property - it is over 150ft from outside tap.

I will be taking ken_adrian's suggestion and leave the forsythia as is, and add some yews as Smivies suggested.

Here's a pic earlier this year

Those forsythia are thin due to the site conditions there in that spot, and not because of where the planting is located geographically. The same site where other shrubs - including yews - will also be affected by the light exposure and rooting environment, not produce the growth and appearance that they would in a more favorable situation. To get a significantly more substantial screen you will have to reduce the sources of shading to an adequate degree, take steps to ameliorate the seasonal drought. And address a possible less-than-optimal soil fertility that may also be present.