While many plants are propagated by clippings taken from the leaves, ferns are instead propagated through taking clippings from the fleshy root, which is known as a rhizome. Root clippings are a more reliable way to propagate a fern than the other option, which is growing the plant from spores. Taking a rhizome clipping from an existing fern gives the parent fern more room to grow, while also producing a new plant
Dig up the fern with a trowel, taking care not to cut into the fern's thick root with the trowel.
Gently loosen the dirt from the root, brushing away most of the soil before proceeding.
Locate a protruding knob from the parent root. In a mature fern, there will be several small knots which may or may not be growing fronds on the top.
Cut away one of the protruding knots with a very sharp knife.
Replant the parent fern wherever it was. It will now be able to use the resources where it was planted instead of having to compete with itself.
Fill a pot with equal parts potting soil and peat moss.
Bury the rhizome in the pot about 1 inch deep. If there is a frond sprouting from the top of the rhizome, bury it so that the base of the plant sits level with the soil.