Thanks for the response. The owners who live there now arent the ones who built the deck so im not sure about their demeanor. If i did plant leyland cypruss, how far would they come into my yard? How wide do they grow?

What are the shrubs that appear to planted on the edge of their property? My first choice in your shoes would be to encourage THEM to plant the screen. They are likely to want it even more than you. They don't want to sit on a deck overlooking a jungle gym, yard materials, yapping dog, etc. If is quite likely that the shrubs already planted there are intended to provide them privacy. If so, you don't want to block sunlight that they need to thrive. You also don't want to waste money or precious space duplicating their screen. Consider yourself lucky that it's a deck, not a pool or a trailer or a junk pile, and that you may have saved yourself a bundle on a landscape divider that will benefit you both. They may even turn out to be nice neighbors, an amenity worth more than anything in my rather long experience..

Leylands would grow approx. 10 ft into your yard if you kept them full to the ground. However if you remove the limb to just below deck height they would barely encroach into your yard.

Leylands on the US East Coast avg 30' h x 10-15 ft wide.

"Leylands on the US East Coast avg 30' h x 10-15 ft wide."

Most likely because they die off from various fatal canker issues before they come anywhere close to maturity. Or they haven't been planted long enough to grow to their expected size. If in a good environment and kept healthy, these trees can live as long as 150 years. And will continue growing all that time. While a select few cultivars will have a slower growth rate or narrower spread than typical, it would be a bit foolish to assume the trees will get no larger than 30'x15'. 50'+ is common and often with a very wide basal canopy spread......25' or more is not uncommon. And since we have no idea where the OP is located it makes more sense to err on the side of larger, wider growth than it does on the much understated sizing quoted above.

btw, it is a pretty standard horticultural rule of thumb that the faster a tree grows, the larger it grows. And Leylands have a very fast growth rate.......3-6' a year after establishment.........so I wouldn't plan on a 30'x10' tree for very long :-))

As I mentioned, you can plan on 30' x 10' tree if you are on the east coast (disease affects those growing in shady conditions). However, rather than debate Leylands as screens. There are many other screening plants that accomplish the same thing....Holly, Juniper, Wax Myrtle, Chindo Viburnum, Ligustrum, Cryptomeria, Silverberry Eleagnus, Anise, etc.

https://plants.ces.ncsu.edu/plants/all/viburnum-awabuki-chindo/

"you can plan on 30' x 10' tree if you are on the east coast"

No. You. Can't. Period. Even local nursery sources quote larger sizes. But since we have no idea where the OP is located, it doesn't really make much sense to make any specific plant recommendations.

I do not agree with your assessment of Leylands on the East Coast. I have been a very successful designer & contractor here since the early 1980's & know the climate & plants for the east very well. I defer to you on growth habits of plants in the Pacific Northwest, but not on the east coast.

As for recommendations, there is no reason not to suggests plants, which will give Eric B a chance to look them up in order to see if they are suitable to his climate & sense of design.

Try making similar remarks on the Conifers forum. Or the Trees forum. A great many east coast gardeners, some extremely able and experienced, post routinely on both forums. And their assessments of leylands does not match yours. Nor does the size expectations quoted by most online retail sources for that area. There is nothing magical about the east coast that would limit growth.

It also important to remember that woody plants never stop growing at any predetermined size. They will continue to grow until they die. Not always at the same rate as when younger, but they will keep growing and enlarging in both height and spread.

Is it possible to know more about your own yard? Path of the sun, general climate? You already recognize that whatever you plant will take up space. It will also drop debris and create shade. Will you be happy with a big row of dense tree forms that cast dark shade, killing off the grass underneath? Think this through before you plant and live to regret the outcome. People don't use decks nearly as much as they think they will, if that's any consolation. Kitasei has a point (see above) -- much nicer to look at a nice (empty) deck than rusted cars on blocks, a giant RV, or the Mack truck I saw in a driveway, or a tangle of dead tree limbs -- all scenes from my dog-sitting walks over the holiday. That said, visualize Embothriums advice from his/her first post above, paragraph 3. You want a garden you can enjoy, not a defensive response to someone else's garden that ultimately makes you unhappy.

Gardengal I put my experience & knowledge up against any of them, period (to use your phrase). I am now done discussing this issue with you.

Thanks for all the suggestions. I live in S Carolina which is a humid subtropical climate. I'm not too sure about the path of the sun but my backyard does get plenty of sun.

We still don't know what are already planted along the line. Your yard is small so your objective is to plant the densest screen no taller than it needs to be - I'd guess 15 ft? Since you are in South Carolina, wouldn't large rhododendrons fit the bill?

Those are Cleyeras I planted but they aren't really growing as fast as I'd hoped.

So those should fill out exactly the area you want to screen -eventually. Be patient! You could add a small deciduous tree that would branch out above their future height thst would add to the screen effect in the meantime. You might add one in the right corner to screen the other house as well. Consider your screen underway and turn your focus to a gorgeous border in front of it that will draw your eye downward.

Based on the look of your lawn, Eric. B, I'd suspect you're not being generous with extra water for the Cleyeras. It makes a huge difference in plant growth rate and I know for a fact that Cleyeras will kick some a$$ in that deptartment if they get it. They could probably screen the foundation area of the deck in a couple of years. If that's not fast enough, you could trade out for something that provides more height. I would not use Leylands though, because they they would soon overwhelm with much more height than necessary. You'll need something taller than Cleyera in order to cover the "lean-to" shelter that sits atop the deck. I think the standard Arborvitae would be an easy way to take care of that portion.

The "deck" looks all the world like an above-ground pool. There would not be any other reason to raise its level way above the first floor of the house. Are we sure it's not that. (Still, it doesn't change the screening needs.)

Not to stir the pot, but have you checked with your local code enforcement to see if the deck was done by permit, and if it adhered to all setback and height requirements? If not, the issue might be resolved (in my town, at least) by having the town contact the neighbor about the violation, and require them to seek a zoning variation or remove it. THAT would be your opportunity to magnanimously accept relief in the form of a landscape screen. Nice screen, nice price (their cost or perhaps at least shared), nice neighbor (you saved their deck!)... Worth a call to town IMHO.. If Yard is right in his suspicions that it is a pool, well in that case I would go for the leylands. A triple row. I am buffered by six acres but there is nothing I can't stand more than the sound of happy children shrieking and splashing when i am hot!

Last time I'm going to mentions Leylands in the MidAtlantic/Southeast. The 59 footer at William & Mary, which is down the street from my home, is an extremely rare exception. Leylands in this area average 30ft high x 15 ft high. That tree is very old & atypical of the average Leyland population. The area does not have a marine climate & is subject to temperature swings & extremely high humidity, not conducive to champion size leylands. As noted in the link: "Comments: The tree is healthy and sound. It is protected from harm in this location. New Virginia state champ."

And a 72 footer in Longwood Gardens, PA.

A 50 year old stand in Richmond on left side of road.

I realize you are desperate to be correct, but you need to remember that I said the average, not champion, size Leyland is 30ft x 15 ft. I have planted these trees in Virginia for the last 30 years for clients & have seen what they do. You can always find exceptions if you scour the internet, but that does not give you the real picture of their growth habits here.

They can also be limbed up from the ground which would make them suitable for the space even in old age. Sheering in perpetuity is not needed. I guess we are going to have to agree to disagree.

I also mentioned Holly, Juniper, Wax Myrtle, Chindo Viburnum, Ligustrum, Cryptomeria, Silverberry Eleagnus, Anise, etc. as substitutes. All are well suited for South Carolina.

Thanks. For the leyland i should plant about 10 feet in would you say?

Eric, just follow the diagram & you will be happy with the result.

I think that they have such a high deck because of the slope of the property. If they hadn't built a deck, they'd have no place to even have a table, it's a high slope.

To the OP, rather than plant a tall fortress of trees that will take space in your yard's depth, maybe you could do something closer to the area of your backyard where you spend the most time? Maybe a nice trellis with an evergreen vine or even decorative panels to surround your seating area? You'd be able to get away with a shorter and narrower screen if you situate it close to the area where you spend the most time. As someone else mentioned above, people rarely spend as much time on the deck as they think that they will when it's built. Possibly most of your time, you would have privacy in your yard.

What about a trellis or arbor with a fast growing vine?

RE: Leylands... we just cut down at some expense a single row of Leylands. They were planted 19 years ago, 2 feet each, single row. Eastern TN. I had them topped 12 times. I repeat, 12 times. You should not top Leylands, but they were getting out of hand. Also had them cut back in the front 12 times as they were encroaching on our small yard.

Below is the fellow who cut them down, his wife was 5' 5" same height as myself. As you can see, even topping them 12 times over a 19 year period, they reached 22' easily - they would have been much taller. These were not healthy growers, grew in clay soil, never fertilized, and did have the canker disease, and trimming/topping them made the weak.

ETA: I planted mine 15 feet apart to allow for 'breathing room' between. Due to the incredibly fast growth and overcrowding, several died.

We are replacing them with slower growers, and not Leylands.

Of course.

Didn't read all the way through the thread, but whatever you choose (Have home on Cape Cod and our Leylands are HUGE and our Hollys are amazing, but a couple Leylands in the shade did die of disease) just make sure you plant well back from the property line so that the final diameter of the tree is within the bounds of your property. Any branches that extend over onto their property they will have the right to trim, as long as they don't kill the tree, but generally speaking trees and property lines make lousy neighbors and can rapidly descend into litigation. 20 years ago In a former life ran a mediation/arbitration firm for a real estate bar association and we used to joke that there must have been a simultaneous sale on arborvitae and chainsaws at home depot as we would end up with a ton of the exact aforementioned cases . In the legal realm, real estate is second only to divorce in emotion. Lesson of the day.... good tropical hardwood fences make good neighbors!