That's exciting that the asparagus is establishing so well.
You will want to cut and remove all of the dead ferns asap (including the ones you mulched with), and put them in the trash as they can harbor insect pests and diseases. 
For edible gardens sanitation and clean up of debris at the end of the season is recommended. 
It is best to cut and remove ferns after the first killing frost in fall. 

Here is our page on Growing Asparagus: 
https://extension.umd.edu/resource/growing-asparagus-home-garden/

We have pages for each of the commonly grown veggies in Maryland: 
https://extension.umd.edu/resources/#!/category/3/subcategory/828


Christine

Thank you so much!  I'm away from the garden and won't get to it until late next week (so another 8 or 9 days).  Will I have damaged anything by waiting a little longer?

Probably not. Just get to it when you can. Asparagus beetles are the main concern and you can learn about them at the link above.


Christine