The tallest grass to grow in Britain is Miscanthus x giganteus. But that only grows to about 12 feet in rich soil. Mine reaches about 10 feet. Trouble is that it has to be cut down in Spring so until it grows you have nothing to look at. Also the stems will not rot easily. We either take them to the Recycling place or burn them. Bit of a nuisance really.

I think you have posed quite a conundrum. You say that you want some sort of screening at the end of the garden but not enough to take the light out of the garden and you want it to run along about 100ft. Any hedging which would be fast-growing could end up being unmanageable. I would suggest that something like Juniper 'Skyrocket' planted in a line with space in between would be my solution.

You could look at Taxus baccata 'fastigiata' which will eventually reach the height you want and more - starts out quite narrow,but like all plants, will get somewhat wider as it matures and gets taller.

How about building a frame & then put a variety of climbers & plants that will trail down?
With netting you could mix tall climbers that trail down with smaller plants that climb up to mix, all colours & flowering seasons could be an option!

Along the same lines I was thinking of trellis with flowering cllimbers.

15 to 20 feet tall is a heck of a height for a decorative screen of climbers. There would be a major stability/safety issue with anything that high. Also the shadow cast by it would extend a long way.

I agree with Owdboggy on this - that sort of height for a fence or trellis isn't really viable, especially once its laden with the weight of various climbers.

Oops - forgot there was a height requirement.

Perhaps you could think about building some kind of platform or wide wall across the area to give a bit more height and investing in huge tubs to stand on it to contain the bamboo that you would really like to have and which certainly would look attractive and let the light through?
Probably a daft idea, but I'm full of those!

Thank you all for your good advice. As usual you have come up with some good ideas that I had not thought about. There is a fish farm at the bottom of the garden and some of it looks lovely but the area we overlook is quite industrial and could do with plants to hide it. Wish me luck Cecelia

Let us know what you decide in the end, Cecelia, and good luck!

I am wondering why you need something so high? Unless the Industrial site has buildings very close to you I think you could get away with something less high. In Edinburgh near the Botanic gardens one householder has built a screen from eucalyptus trees. He has threaded the branches through from tree to tree so that it is not wide but could be as high as you wish. The trees are 4' apart and on the border between the boundary with the next house and his drive. When I saw it first I thought it was a row of lime trees, Tilia cordata, but it was evergreen (grey) so I took a closer look. The tilia is a native tree and can be seen bordering fields etc. When it is pleached it looks great. Pleaching is where the tree branches are interwoven.

I need the height because our garden is very steeply sloped and the fish farm is at the bottom. If we had a normal 6 foot fence we would just be looking over the top of it. I thought about putting up a normal fence and planting 3 prunus chanticleer trees in front of the fence. They would help hide the fish farm in summer but not so much in winter when the leaves fall. I will have a look at eucalyptus trees to see if that would work. Thank you for the advice I will keep thinking about the all the different ideas.

You could ask your local council if they would allow an 8' high fence because of the unique circumstances. Have a look at this web site
https://www.jacksons-fencing.co.uk/fencing/family/hit-and-miss-family
It shows variations of a hit and miss fence which acts as a wind break but affords both sides privacy and both sides look equally attractive. It allows light through between the offsets.

Certainly Eucalyptus grow very tall very quickly and aren’t too dense. If your site is very windy, you will need to stake them though because. They are terrible tumblers having a long tap root and not much in terms of wind resistance when immature. I found This out the hard way! I’m wondering about some ofthe larger Acers...Acerrufinerve springs to mind. Its a beautiful snake-bark maple and grows 8-12m. I’m also reminded of the beautiful Hoheria sextylosa I had in my first garden. A beautiful evergreen to 8m that grows fast and is smothered by white flowers from top to bottom in July. It needs shelter though. This is a tricky issue for sure, and Ithink you are wise to keep away from Bamboo. But I think some good and suitable trees are the way forward. I’d recommend you speak to the owner at Bluebell arboretum. He is extremely knowledgeable and helpful...or your local tree nursery. Good luck.

Yes I will contact Bluebell arboretum and have a look at the plants you have suggested. I don't think its something I can make a quick decision about without making a huge mistake. I am really pleased with all the good ideas I have been offered and the helpfulness of the people who have responded with advice. Thank you all very much. Hopefully it will be resolved by this time next year and I can enjoy the garden. Cecelia