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

You wanted to build within the next two years almost nine years ago - does a bit more time still matter now?

Yes, that shows you how planning goes... In 2017, unfortunately, I could not foresee that at the beginning of 2019 we would have a child on the way, with whom we did not want to start a new building project directly, and when we were finally ready, Corona came and almost destroyed the availability of building plots. Therefore, we are glad that, through a lot of luck, we have now gotten a plot of land.

maybe you overlooked such a special requirement (?)

No, definitely not. I have studied the development plan thoroughly—from the number of open spaces to eave height, roof shape and angle, to the right of the city to place nonprofit supply facilities in the middle of our property at any time—until we sell it. Totally insane, but believe me, there is nothing like that. However, I know that from other areas. There it sometimes states that within a 2m distance from the property boundary at least X plants from categories A, B, and C must be planted, but at least from two categories, etc. In our development plan, areas are also marked that must be planted—with even the trees drawn in. But not on our property.

If the building authority in your case actually has no legal basis to require this open space plan, then conversely, because its absence, they cannot refuse the approval—then they should first dare to do that.

I’m afraid they will. I have now studied the municipality’s statutes thoroughly as well. There is all sorts of things... from the setback area statute and the parking space statute to the core town redevelopment statute, statutes for preemptive rights, pigeon regulations, advertising system statute, and the poster ban ordinance. There is also a property maintenance ordinance, in which I would have most likely expected a regulation, but here it only regulates when and how to weed and remove moss or when and how to remove leaves or trim one’s hedge—but not that you have to have or plan one. From the other legislation, I am not aware of any obligation for us or any right for the city... I will call them very politely tomorrow, ask what requirements they have to avoid unnecessary ping-ponging, and then cheekily ask on what grounds the demand is based, so that I can orient myself somewhat to these requirements. Then I’m curious...

Also a kind of pavilion, also covered with ivy,

The eternal and deceptive weed.. I thought you didn’t want any work?

Well, I see it this way: everyone is annoyed by climate change and many have or will have a significant financial loss because of it.
But it’s always supposed to be the others who do better – while one exempts oneself from the duties.
It’s simply like this: straightening, sealing, and no deep root system make the damages become enormous in the first place.
Hopefully there will be a change now – I can live with something like this being included in insurance: whoever does not contribute their part will lose out and have to pay extra.
This doesn’t help you now, but it might open the eyes of one or another that much depends on us and our behavior, that something no longer remains what it should and must be – namely a ground on which nature has a higher value than we do ourselves.
Of course, it’s better if one expects such sensible and nature-oriented land use plans from oneself and does not doubt them.

The eternal and deceptive weed.. I thought you didn’t want any work?

I never said no work. But within a manageable scope. There is probably a difference between trimming some ivy and cutting a 60m hedge from inside and outside (so 120m) and having to haul the stuff away. For that, I had to buy a new car with a trailer hitch—and a trailer. But yes, that’s all true and yes, that doesn’t help me. We are leaving a gas heating system in a poorly insulated old building behind and (apparently eventually) moving into a passive house with a heat pump, photovoltaic and solar, designed to operate almost CO2-neutrally. Also, not a single tree was cut down on the property; only uncultivated farmland was developed. The flat roofs will be greened, and otherwise I have nothing against plants in the garden, front yard, or anywhere else. The wallbox is planned for the garage, the BEV is already available. Of course, more could be done—there always is. If it were up to me, we would have bought a property in Costa Rica, would feed ourselves from our own garden, and draw electricity generated from 100% renewable energy (hydroelectric power plants), while the government massively protects the forests and the military has been abolished. Then gardening makes sense, and nobody demands planting a tree in the garden that is regularly pruned with a chainsaw, whose fallen fruit ends up in the compost, and whose leaves are burned, while the forests around are cut down. But I am certainly not aiming for an ethical-moral discussion now.

I did not say I have no work. But within a manageable scope. There is probably a difference between trimming some ivy and cutting 60m of hedge from inside and outside (so 120m) and having to haul the stuff away. Then I would also have to buy a new car with a trailer hitch – and a trailer.

You have almost no work if you just let it grow. We've been doing that for 10 years. We have deliberately planted our bird protection hedge 3m away from the fence. In between and in front, lots of trees. This year, for the first time, I pruned 5 branches from a blackthorn because it was crowding the linden too much. It was shredded on the compost in 10 minutes. Usually, those who shout "no work" first plant a thuja hedge along the fence and lay out the "dead" turf.

BNatSchG §17 para. 4 sounds like the law you are looking for. But I am not an expert. Every construction is an intervention in nature and, as far as I know, the environmental office is always involved in granting the building permit. You can also specify bushes and flowers as planting. What, however, in my opinion, is not allowed is to specify nothing at all.

But it is not about front garden flowers, but about the root system of the respective trees.