We recently moved into an apartment with a garden, and there are some tall trees in our neighbor's garden that cast a lot of shadow in our yard (and one also causes a lot of allergy problems).
Almost our entire garden is surrounded with (what I think are) cypress trees. We keep them trimmed at about 180 cm. I have a love-hate relationship with them. On the one hand, it's nice to see the green all year-round and to have the privacy they create. But on the other hand, they also get full of very visible spider webs very quickly and do make the ground very acidic.
Anyways, I think you should definitely talk to your neighbor. You and your garden shouldn't have to suffer just because they want more privacy. You deserve to enjoy your yard, too.
Maybe you could call your Gemeinde to ask them what would happen if you decline your neighbors' plans?
Good luck!
Our UK garden was surrounded by a paddock. When the neighbour sold the land for house building- a bungalow was built quite close to our boundary, which consisted of 4 to 5 m tall mixed trees, lilac, mexican orange blossom, forsythia, elderberry, hazel, beech, etc. The people who bought the bungalow immediately began to complain about the hedge and made request for it to be cut, again and again. When I stated that the hedge was there before the houses were built, when they first came to see it, when they came to see it again, when they signed the contract, when they moved in ... their reply was 'but that was the only one we could afford, it was much cheaper than the others' - doh, I wonder why. We sold 5 years ago- and the hedge is still there- it is indeed protected by law as it is a very old mixed hedge.
http://v2.suedostschweiz.ch/epaper/p..._01_2014-08-28
A dispute about permission for an entryway overhang has gone on over twenty years , outliving both the original parties, and is being waged still by the widow and the next generation. The dispute has escalated beyond the overhang to include flower planters, privacy fence, a garden gate - and is making it's way up to the Bundesgericht. The cost over the years has been ca 100K.
In my humble opinion: When faced with this kind of thing, do what you can to come to a compromise that both of you can live with. Few things are worth 20+ years of neighborhood warfare.
Here we have the boundary rule...... for every 2cm of extra height over 1,5m one must forfeit 1cm from boundary. So we forfeited 30cm of land to go up 60cm.
When we have the money to build a solid wall of 1,5m - on boundary, bricks being 30cm deep, on our side of wall we`ll mount a strip of bamboo fencing to cover the extra 60cm. Thereby cutting out having their weeds growing on "our" 30cm of land, and keeping the height within regulations.
(We really do not like having to see our neighbors - (they`re the "ones from Hell" of previous threads of mine - when I win the lottery I`ll buy their house and demolish it).