Hello!
The "bulbs" are probably next season's fronds still curled at the crown.
I grow the native Dryopteris here, and they handle the cold weather just fine.
In a container, they might be a little more sensitive, but I wouldn't think it a serious issue.
I wouldn't cover them with heavy bark mulch, but a layer of natural leaf-litter should be fine.

Josh

Hi Josh, So, these are actually next season's fronds. That is very interesting. They are above the soil line, should I be adding more soil to cover them?

Hello!
To be honest, I've never worked with Dryopteris normalis specifically.
However, with my other ferns, next year's fronds are all bunched together in the crown
with their wooly, golden-brown coverings. I always keep the crown of my ferns above soil-level,
although I will push some leaves against the base during winter.

Can you take a picture of the crown of your fern?

Here are some pics to compare - this is a Woodwardia (Chainfern).
These fronds have already started opening, as can be seen, but they are much tighter
during the Winter (pics taken in March).

{{gwi:615081}}

{{gwi:615102}}

Josh

Another couple pics...

First, a pic of the leaf-litter that I leave around the fern crown during the winter months:

{{gwi:599267}}


And a better pic of the fronds still curled tight against the crown:

{{gwi:599271}}



Josh

Josh, these photos of your ferns are lovely. Yep..this is exactly what I was referring to. I've been busy with hallowe'en and birthdays this past week, maybe tomorrow I can take a pic of my ferns. I'll put some leaves around mine too for the winter. Thank you for helping me with this.