I have two heirloom ferns. They were my grandmothers. My aunt cared for them after Grandma died in 1982 -- my aunt divided them regularly. Now my aunt is also gone and I have two of the ferns. They need to be divided. My cousin said that her mom basically cut them in half with a big knife and put them in new pots... Is that the best way? Is there a particular time of year that is better than others for doing this? Thanks for the help.