Burdock Root

Does anyone have experience with preparing burdock root? After six years of fighting what I called the weed from H...,
I I.D.'d the plant as burdock. A little web research turned up a few recipes, but not a lot of helpful harvest information (when, would be good) or preparation information. I did prepare some in a stir-fry with carrots and it was good but some of the roots were so fibrous all that could be done was to spit them out. So, clearly some that I thought were okay were too large or old or something.

If you can't kill 'em, eat 'em.