Jane, the key thing here is that celandine has a short and precise season of growth, from midwinter to May, then it disappears in summer when roots are dormant.
Therefore summer mulches do not kill it because it’s not trying to grow.
Even now it’s getting late to mulch though still worth it – cardboard and a thin layer of compost to weight it down.Then remulch after Christmas as soon as you see new celandine, which will be weaker.
You could plant asparagus crowns in this bed but would not then be able to mulch 100%, so if you have another bed for asparagus, I would plant in that.
