When is the best time to prune back the asparagas fronds that have been hanging out all summer? Should I mulch with compost after I prune?
Marion County Oregon asparagus
Thanks for your asparagus question. This Extension article has lots of information about asparagus and, although not specific to your question, it indicates:
"Do not harvest the spears the first spring of planting. They should be left to form "ferns," which provide food for the plant. The second spring after planting, a few shoots can be harvested, but only for a week or two. Leave the rest to feed developing roots. The third spring and thereafter, harvest spears until mid-June, then allow the fern to grow and keep the root crown healthy."
By now, though, the ferns have probably produced as much 'food' for the roots as they're going to, so they can be cut off and composted.
The article doesn't address it, but asparagus can and should be mulched, as with other perennial vegetables. Here's a link to a short article on that. Hope this is helpful for you.
I read the article which is a nice read for spring pruning, but I'm looking for information about pruning the ferns this fall to "winterize" my asparagus beds.
in your response you say that the ferns have probably produced as much "food" as they are going to. So I don't need to wait for the ferns to start to die back or anything like that? How close to ground level should they be pruned back to?
Pruning and winterizing are really unrelated. You prune to remove dead or unproductive tissue (which these ferns have become since they are done photosynthesizing). Winterizing means adding mulch to keep the roots protected over the winter. Pruning won't winterize; winterizing won't remove the ferns.
You don't have to wait any longer for the ferns to die back. Prune them now, about one inch from the ground. Then apply mulch around (atop) them. Asparagus plants don't like to compete with any other plants, so--regardless of the season--don't plant any other plants near or on top of the asparagus roots. Good luck!