In a bucket or large planting pot, combine equal parts peat moss and potting soil. Dry peat moss is sometimes a challenge to moisten, so stir the mixture as you add water. Mix enough to fill two pots if you'll be dividing the foxtail fern.
Fill the new pots halfway with the moist soil mix.
Slide the foxtail fern out of its pot and lay it on the work surface. Divide it with a pruning saw by slicing it into smaller plants, each with its own roots.
Plant the foxtail fern or ferns at the same depth as they have been growing. You may need to add more soil to the pot to get the foxtail to the proper depth. Fill around the root ball with soil until the pot is full to within 1 inch of the rim.
Water the ferns slowly so the soil and root balls absorb the water. Stop watering when water runs from the bottom of the pot.
Set the foxtail fern in a spot with bright but filtered sunshine.