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

May I ask what kind of hedges you have there?

It is probably less about what kind, and more about how. We have given our hedge 6m of space to the front and back. Most bushes don't get much wider. My husband deals with new shoots using the lawnmower. The result is that we have never had to trim the hedge. Otherwise, we have common native varieties like blackthorn, hawthorn, crabapple, wild roses, serviceberry, privet, dogwood, hazel, viburnum, and a few others.

That seems to be heading in that direction, yes. However, I don’t see how that has anything to do with our building permit.

Again: Your building permit automatically means an intervention in nature. In these cases, an examination of admissibility by the environmental office is always required. But they can’t review anything if you don’t say what you plan to do in your garden. That’s why there is the above §, to force you to make a statement. However, no one says you have to plant trees. Basically, a balance is usually prepared. Your plans are evaluated in total and compared to the current state. For a positive decision, your score should be higher than that of the existing greenery. You might achieve this equally with a flower meadow as with a forest. To what extent the colleague on site now has further specific requirements, you can only inquire. It is quite possible that a nightjar lives next door. Then you’re really in for some fun.

But for that, it would be good to have guidelines... But there are none. Neither does the development plan say anything about it, nor any statute or anything else. That means if the authority takes a stand on it, they will always say: too little, wrong choice, in the wrong place...

I see it more from the perspective that because there are no guidelines, the office wants to know what you intend to do.

Again: Your building application automatically means an intervention in nature. In such cases, an examination of admissibility by the environmental office is always necessary. But they cannot assess anything if you do not say what you intend to do in your garden.

For the individual construction project, I have not heard of this yet; I only know it as the involvement of the TöB in the preparation of the development plan. And there are also cases of exemption.

I have not heard of this for an individual construction project; I only know it as the participation of the public authorities in the preparation of the development plan. And there are also exemptions.

I do not know of any construction project where a copy of the documents is not automatically sent to the environmental office. At most, in simplified procedures where the builder explicitly adheres to the specifications of the development plan. But in that case, the environmental office’s approval has practically already been obtained beforehand.

Whoever has 3,000m² of land might be able to let the hedge and the trees grow wild.
On 600m² that's not possible; you have to cut them, and annually at that.

There’s no fooling yourself, it’s work.
Which is why I fundamentally don’t understand what you want with a detached single-family house with a garden in view of retirement, without the means to hire a gardener.
Or are you only in your mid-30s? Why then think about your 80-year-old self?

For the individual construction project I have not heard of that yet, I only know it as the involvement of the TöB in the preparation of the development plan. And there are also exemptions.

As I described, it was a significant component for us 3 years ago, which was strictly necessary to obtain the building permit. According to the building authority clerk, our building plan could not have been approved without the OK from this nature conservation office (or whatever it is called depending on the federal state). There was no letting it pass, that was a hurdle.