We have a cardboard fern in the ground for the past ten years or so. Lately, we have notieced the fern limbs are turning yellow. Can you tell us what to do for it?

Welcome to ATP.

Can you perhaps add a picture and a little more info?

Do you fertilize it? Has the environment around it been altered? (more or less sun. water , colder than usual temps, etc)

This link has lots of info on the Zamia furfuracea cardboard palm which may also be of use to you.

http://www.florida-palm-trees....

Is it getting more sun? less water?

By Cardboard Fern do you mean Cardboard Palm (Zamia furfuracea) ? This plant is drought tolerant once established so the yellowing leaves could be caused by all the rain of late.