In terms of removing the existing trees, I'll likely just cut them down and hack the roots a little under ground level and then leave them.
Where does one buy such hedges in Switzerland or Zürich. As I have never planted anything in my life, any advice on how I should do it?
Most cantons and communities define the height allowed at the border, or at a set back. Some define the type of planting allowed or forbidden.
Some communities require the bordering neighbor's permission to plant on the border, and some even require it if you plant set back on your own property.
Be aware that some communities allow for a 5year objection period, so getting your neighbors on your side now could save a lot of work and expense later.
But assuming that you have already done that:
Do you want an eveegreen hedge or a deciduous one? Do you want the hedge for privacy, or as a border, or something else?
Why you want the hedge would determine what you should plant.
What kind of sun? What kind of soil?
What is your budget per meter?
These will be things to consider.
For good value for money, look at Landi. The one in my area has a good garden selection, and the staff are pretty good about advising wrt local growing conditions.
Also look at Hornbach, you can find some good deals on healthy plants there too.
End of season Coop B/H will have some good sales...but IME you do need to be able to recognize what is and isn't a healthy plant.
For the border where i need to block the mutt's view i have planted a rather boring Thuja hedge. Thuja are sometimes tricky, in the wrong amount of light or heat or wrong soil they can die quickly. But they are a quick growing plant, hence why you see them so often as a border.
For the rest of the garden I have 'usable' hedges: a stand of blackberries, another of raspberries, a row of blueberries. These are planted against a fence (the mutts, again), so the fact that they lose their leaves or need to be cut back in winter does not matter.
There are so many possibilities for a hedge, it all depends on what you want.
Why not spend some time looking at garden catalogs, then go browse around a large garden center to get a feel for what is available.
Good luck... And remember: good soil prep is as important as the planting itself.
ETA:
Also ask at a local garden center if the plants you are considering are more susceptible to disease at the moment. For instance, boxwood is a popular plant for a low-growing hedge, you see if often around here. It's usually a sturdy plant but about three years ago a boxwood blight hit, most of us lost our bushes. Some 10 years ago firebrand hit our area, many fruit trees (these too are sometimes planted as hedges) and cottoneaster (planted often as a rock wall border) were lost. Cottoneaster is now banned in our area, btw.
We ended up getting some lebensbaum (cypress)from a place around the Bodensee. Prices are lower and transport is a bit higher. (We're in Winterthur). I guess those are Thuja.
Here is the place we used
https://www.heckenpflanzen-schweiz.ch/
But these guys might be good as well
http://www.pflanzenzentrum-bodensee....ecken-zentrum/
We have a Terrasse and needed a privacy screen. Our plants are in big pots. They came with the roots in burlap and wrapped in wire. We remove the wire and burlap and planted the trees. Some places might deliver them in pots instead of root balls.
We paid chf 30 per tree plus chf 160 for delivery. The trees we looked at in jumbo, for example were twice, three times as much and chf
120 to deliver.
Since I planted in pots, not much advice there.
Funny thing about terraces. My neighbors have trees of 2m or more all over the place. We're going to keep ours trimmed to 2m. I guess excessive height is a problem but 2m seems ok.
Definitely one to avoid because of this and the blight.
These grow more slowly (Buy bigger to begin with) and only need a trim twice a year. They grow really dense and are very, very robust.
They also look great when cut:
My next hedge is going to be Yew.
Simple ways to prevent this are...
1. When you cut the tree, immediately apply weed killer with a paint brush to the freshly cut surface.
2. Or, cut a slit or drill a hole in the exposed stump and hammer in a piece of copper pipe or copper coins.
I've used both methods and they both work.
Youtube is your saviour
Whenever I've hit a gardening issue I wasn't familiar with, I watch a handful of youtube videos on the subject. My favourite gardening youtube channel is an Aussie one called 'Gregthegardener'. Besides having a funny, no nonsense approach, I've always found his advice very useful.
If you're planting a new hedge, you really want the roots of the new hedging plants thriving in good soil with plenty of compost rather than in tired, thin soil full of dead wood.
You'll need to get the roots out and enrich the solid before planting new hedging as they make the soil very acidic ( or alkaline I can't remember which now) and it's difficult for other things to grow near them.
If I were you I'd plant a mixed hedge alternatiing photinia red robin and viburnum tinus. They are both evergreen but add some colour and don't need a lot if maintenance. Laurel needs regular trimming to keep it in good shape.
The prices seem very reasonable for what I am looking for - Carpinus betulus - Hainbuche hedge.
Normally I just give it a try to unknown shops, but here is a bit different as the shipping fee is probably quite high, therefore it doesn't make sense to order a small trial order first and then the rest of the hedges when I am convinced of their quality.
So if you have any feedback about this shop I'd be thankful for any info.