Avoid weeds on excavated areas

With thistles, I would do it before filling - once the seeds start flying, it's hardly possible to get rid of them again.

Thank you so far, I am currently just looking at tarps and have found a silo tarp that is also roughly the right size and lightproof. I think I will order it and lay it out once the ground has dried a bit.

I would dig out thistle.
Cover with a tarp or use chemicals or leave weeds so short that they do not set seed.
Some weeds you only spread properly by tilling, e.g. [Giersch].

It makes sense to apply chemistry after the topsoil. It can also be sown right away. Whether you want to do that is something you have to decide. Or just cover with a tarp for 1-2 weeks. You will always have weeds. Frequent mowing and uprooting. In the current state, it doesn’t really help. The light germinators will all be covered later anyway.

It makes sense to use chemicals after the topsoil. You can also sow immediately. Whether you want to do that is something you have to decide.
Or just cover it with a tarp for 1-2 weeks. You will always have weeds. Frequent mowing and digging out.
In the current state, it doesn’t really help. The light germinators are all covered later.

It helps insofar as it prevents this year’s harvest from spreading on the property and later being blown back onto the area. Especially with thistles, you should prevent seed dispersal. But I am also a burned child here – our landscape gardener assured us that 30 cm of fresh topsoil is enough to prevent wild growth from coming back. Everything came back.

But the stuff definitely did not germinate through the 30cm but was either in the humus or simply ended up there again.