Fife,
United Kingdom 
We have a variety of ferns which are more than 20 years old. The caudex of a number of them is now eight inches or more high and slightly wobbly. We have cut the leaves annually but never cut the caudex. Is it possible to cut the caudex to ground level to make the plant more stable without damaging its growth?
13 Mar, 2018
Do the fronds arise from the outer edges of the caudex or from the middle. If from the middle then I suspect you would do irreparable damage to the fern. if the fronds arise from the edges then it should be ok.
I also have some old ferns and I pull the old withered parts of the caudex away and draw soil up against it.
13 Mar, 2018