what is a fast growing hedge and when can I plant it?

Myrica californica is one suggestion. How wide can these plants get? I also assume your 3m block wall might be an indication as to how high your hedge can grow.

I am going to wait and see what other think. A hedge plant that gets squashed against a wall might have problems with god knows what. Trellis with vines. Same problem. How to trim and maintain.
Ivy used to be the answer, but I view it as a noxious weed.

In CA. we had a more polite fellow called Ficus pumila, (repens). Do a search on it and see if it could survive your climate zone. I guess not. But some alternative might.

I will follow this post.

Griselinia?

A 15ft. wall to me sets up a place to produce colour and even fruit.
Wisteria bought now can be grown on frames in containers. Also many other climbing shrubs or fruit trees. I have said before do you want to look at another one of the 200 greens out there, which would have to be planted at least 6ft. away from the wall.
On the outside I would have Beech which you can buy now for about £1.50 each. I know most of these shrubs or trees are deciduous, but the maintenance is far less and all the leaves make god compost or mulch.

There's an evergreen Prunus - P.lusitanica - which has glossy green leaves on red stalks and has the bonus of cream flowers. There's a variegated form, too, which is quite attractive with cream markings on the leaves. You could consider this for your outside hedge. I suggest this because I have moved one successfully after it was a couple of years old.

I agree with Docbob - trellising the inside would give you so much scope for growing wonderful climbers! I would wait until the wall is up and then have some fun choosing colours and planting!

Escallonia is a good one, tightly knit glossy dark evergreen leaves and the bonus of white, pink or red flowers depending on the variety. It is reasonably fast growing and can be pruned vigorously to any sort of shape, and it is also easy to propagate by cuttings. It is also reasonably priced wherever you buy it from, good luck...........

Laurel is very fast growing and easy to maintain.

P.lusitanica would also be on my radar.I was going to suggest it, but then leaned towards a vine. An added bonus, the flowers smell like taco chips. It will grow wider than the Myrica, but its foliage does a better job in muffling street noise.

http://www.hedging.co.uk/acatalog/product_16932.html Good morning Jacal I would recommend Christmas box here is a link to the hedging or laurel stay clear Leylandi.

And Beech Hedging another favourite .