Growing grass on top of river stone

Question

Im trying to grow grass on top of small stone rocks. If i remove 2 inches and replace it with top soil will the grass be healthy. See image

Thank you

Answer 1

Assuming you mean lawn grass, no, 2 inches isn't sufficient - you need a minimum topsoil depth of 4 inches, but preferably 6 inches for a healthy lawn. Further information here https://www.gardenguides.com/12284756-how-to-lay-topsoil-over-gravel.html

Answer 2

You can grow grass on a thin substrate but without soil depth the roots will be shallow and the grass will die in drought or severe condition unless you constantly upkeep it with extra watering, extra fertilizer, more mowing. Unlike most woody plants, grass doesn't have a taproot, so it has a fibrous wide root.