How do I change a lawn to a flower bed?

I've just done the same thing recently. Unfortunately, you have to dig quite deep. Then you have to turn the grass over so none is showing. The lack of light then makes the grass die. Otherwise, as you have found out, it just grows back.

You may be able to buy a grass killer chemical of some sort, but I'm an organic gardener, so can't help you there I'm afraid.

You can buy black membrane from Builders merchants, which is very cheap. This, once laid down, allows water thro' but not light. This would be good if you wanted to lay shingle down for an informal path, as it would stop weeds growing thro'. Hope that helps. :-)

Well, we garden organically and Roundup since it is inactivated on contact with soil does not seem to us to be a problem in the same way as say insect killing sprays which persist. And sad to say, but if your grass is of the Couch type or Creeping fescue then you will never get rid of it by just digging it in. In fact with couch you actually increase the stuff by doing that. I have just created a new flower bed fom lawn. I sprayed the old grass with Roundup a couple of times and waited until everything in the area had died, then dug t over. I waited until everything grew aghain (from seeds mainly) used Round up again and then when the soil was reasonably clean began planting.
This is how we created our Veg beds 15 years ago and we are still alive!

The worst thing you can do with weeds is to dig them over. Good preparation will pay you but it means a lot of back-breaking work I'm afraid.

I've found Roundup to take so long to take effect that with a large area you begin to think you've missed patches! Weedol will also kill the roots but it has a faster knock down effect which I personally prefer.

Having tamed a disaster area or two myself, I've found the best and ultimately the quickest way for me was to generously Weedol everything on a wind-free day and repeat the next day if possible. (You can forget the spread rates on the packet, even at my most miserly I can usually only cover half the area they suggest). Then two weeks after spraying dig out turfs around 3-4 inches thick, turn them over so no green is showing. I've then covered the turfs with extra top soil because the turfs are often so thick with root that new plants can have a hard time establishing otherwise.

Then once you start planting your flowers you will need to be vigilent for any nasties returning. This is where a daily check with a weeding fork for twenty minutes becomes time well spent. I found it very satisfying, but maybe that says more about me than anything!

BTW Black sheets are good for paths or laid under existing shrubs which you don't wish to disturb too much, but don't plan to rely upon them on their own.

Thought Weedol left the ground unusable for 6 months after?

My first garden my husband just roto-tilled and never again ..... I pulled grass out forever... now I lift the sod off before roto-tilling, it is actually prety easy ... I reuse the sod in bare spots in other areas.... or compost it