Building authority requires open space design plan for single-family house - experiences?

If the authority wants such a plan, it wouldn't be wise to start a big discussion about it. Because even if you end up being right, it will definitely cost you time and nerves. If you google such plans, you will find that something like this could be created with PowerPoint in the same style. And if you then take all the requirements regarding the number of trees to be planted, etc. into account, the authority will surely be satisfied. It also definitely doesn't hurt to deal with the basic design of the garden in the early phase. And if later during implementation you move the trees a few meters or design the path differently, no one will hold it against you.

But it's not about front yard flowers, but about the root system of the respective trees.

What don't you like? It is simply the case that the root system of trees is important for water retention. The sponge principle protects against flooding. As long as you don't build your little house in a Bavarian old town, it is relatively irrelevant (also for the land use plan) whether geraniums or tulips adorn your front yard.

I will give them a friendly call tomorrow, ask what requirements they have to avoid unnecessary back-and-forth, and then cheekily ask on what basis the demand is founded, so I can orient myself a bit by these guidelines. Then I’m curious...

"For safety’s sake, I would like to read it right away in the legal basis" ...

If you google such plans, you will find that something like this could be created with the same look using PowerPoint.

In any case, I would beat them at their own game by including in the plan or its legend: "Planting with selection from the species list according to point 4.7.11 of development plan 815 with ecologically indicated crop rotation." That means you put areas with tree and flower patterns into the drawing and then this bureaucratic fine print into the legend. That already gives the caseworkers wet panties just by reading it and leaves you free to put in other greenery with a rolled justification (outside the breeding season of the stone dormouse, of course).

You have almost no work at all if you just let it grow. We've been doing it that way for 10 years.

May I ask what kind of hedges you have there? I’m not very knowledgeable about botany, but in our current garden the hedge is really overgrowing. This year it was extreme. The branches hung over a meter into the garden and grew over our heads. I was glad I didn’t have to do it myself; I would have had to drive to the shredding yard probably 5 or 6 times. And that’s maybe a maximum of 25m from here. Also, when the trees from the public open spaces protruded so much into our garden that we could no longer open our sunshade, I was told by the city that this year everything is growing so much that they are completely overloaded. I could understand that. But I was given permission to remove the affected branches myself.

BNatSchG §17 Abs. 4 sounds like the law you are looking for.

That seems at least to go in that direction, yes. But to what extent that has anything to do with our building application is not clear to me.

And if you then take all requirements regarding the number of trees to be planted etc. into account in it, the authority will certainly be satisfied.

But for that it would be good to have requirements... which there are not. Neither is there anything about that in the development plan nor in any statute or anything else. That means if the authority wants to, they just always say: too few, wrong selection, in the wrong place...

"To be on the safe side, I would like to read it directly in the legal basis" …

Yes, I will probably do that, thanks. Today I refrained from calling again. I spoke with our architect, who also sees no legal basis for the demand and describes the submission as voluntary but recommends just going along with it to speed up the processing, without worrying because of the missing basis. He thinks the authority probably just wants to more easily evaluate the remaining open space (floor area ratio). And a plan is a plan and not a specification sheet... Whether that is true...?

In any case, I would immediately beat them at their own game with the plan.

That sounds good at first, thanks.

Then you are pretty free, but you can use other development plans in the area as a reference. These will include things like "1 native deciduous tree/fruit tree per every 200m² of property area" and things like "living fences." If you then add these basics and justifications as suggested by 11ant, you will have a plan that will very likely be approved.

He thinks the authority is probably only concerned with being able to more easily assess the remaining open space (floor space index). And a plan is a plan and not a specification sheet... Whether that is true...?

That the area is properly planned and not gradually stuffed with a mishmash of procedure-free monstrosities is probably rightly suspected by the architect as the desired pacifier. But the plan could be considered part of the building application and thus certainly obligate corresponding implementation. Hence my suggestion with the "wishy-washy in the manner of the authority," against which they can hardly object.