Division is the best propagation method for your Boston fern (Nephrolepis exalta 'Bostoniensis'). Even if you don't want to produce more plants, sooner or later it will become necessary to divide your Boston ferns because they don't thrive when potbound, don't store water well and require as much as twice the normal watering to survive this condition. Divide Bostern fern during its active growing season before the end of June and your plant will thank you.
Examine the Boston fern and decide how many divisions you want to make. A large, healthy specimen can tolerate as many as four divisions.
Prepare a pot for each new division. Use containers the same size as what the fern currently occupies and fill the containers with the same potting mix.
Cut off all the Boston fern's older fronds and any that are dead, diseased or damaged. Remove them at soil level. Trim back the remaining fronds by about half their lengths.
Take the mother plant out of its pot. Use a clean serrated knife to cut the root ball vertically into halves. Cut those portions into halves if you want four divisions. Saw off 1 or 2 inches from the bottom of the root ball of each new division.
Plant the division no more than 1 inch below the rim of the new container. As you plant, press the soil firmly into place around the root ball to eliminate any air pockets.
Provide the same feeding, watering and lighting conditions you gave to the mother plant. As soon as you see new growth on the Boston fern division, congratulate yourself on a job well done.