Mulching Boarders

I hope this is not a silly question.
I plan to put a good deep mulch on my boarders in the Autumn. I have loads of my own Garden Compost to use.
This year I had lots of weeds come through which I have dug out and cleaned the soil up. Experts say approx 4 to 6 inches of mulch is best. But will it stop my perennials coming through and what about things that self seed like poppies, nigella and such like.
I would appreciate assistance / advice.

 

The RHS advises a mulching depth of 2-3 inches. 4-6 inches would be too much unless you were protecting dahlia tubers and the like over winter.

 

Mulch will stop the self-seeders from coming up/swamp the seedlings if they're already up. However if you've had your self-seeding plants for a while there'll probably be seeds in the compost (and weed seeds) unless your heap gets very hot and is turned enough that all parts of it get hot enough to kill seeds. Those will germinate if they're on/near the surface of the mulch. I must have put some seeding sticky willy in my compost last year because the area that I mulched in February has produced loads of it. All went back in the compost bin (hopefully before it got to the seeding stage).