I am reworking my veggie garden to the sqaure foot method.. already have one box completed... 4x15.. with more boxes to add.

But here's the question, I have a fairly new asparagus bed.. this will be the third summer, I would love to incorporate them in the raised bed method.. do I need to dig them up? can I put boards around the area and slowly add soil as the asparagus grows or do I need to raise the crown/ root ball? I'm afraid if I have to dig it will set them back.

Thanks