Would asparagus adjust to a border of mulch and compost?
I would like to build a border around my asparagus that is 12 to 18″ high and then immediately, or gradually fill it in with mulch and compost. Will the asparagus adjust to this, or will I need to replant it all?
As you probably know, asparagus planting depth is important to the health of the plant and the quality of the harvest (including a link from the TX A&M Extension for reference); if you’ve been growing it, the crowns are probably already under a decent amount of soil. While your established crowns would definitely adjust to some amount of increased soil depth, I’ve been unable to locate any Cooperative Extension resources giving a workable number of increased depth that would be tolerated. Your best case scenario would probably involve gradually increasing the depth to see how the plants do season by season, and your harvest would probably eventually be fewer, but stouter stems. The worst case scenario would be smothering the plants to the point that the shoots are weakened from the exerted effort to push through too deep soil, or having the crowns rot. Twelve inches *might* be ok if it’s loose and porous and you have vigorous plants, but 18 inches of soil on top of your existing depth worries me.
So, my summed up reply is maybe, but I’m nervous about it and would advise you to go slowly and monitor the plants as you go along.