Ferns are one of the oldest forms of plant life. There are over 10,000 known species of fern, some of which are deciduous and some that are evergreen. Fern leaves are called fronds, and they house the reproductive spores that ferns produce instead of seeds. Deciduous ferns lose their leaves in winter and tend to look ratty over the season when some of them die back but don't fall off. Evergreen ferns are vibrant year-round but they can benefit from cleanups to remove damage and dead fronds. Timing is important when pruning ferns so new fiddleheads (immature ferns) are not disturbed and spores are able to disperse.
Timing is Everything
Pruning of ferns needs to occur after the spores on fruiting fronds have matured and released. Trim them when they are dormant, which is during winter. They can also be pruned in very early spring. Many ferns do not object to pruning at any time of the year. The hardy ferns such as sword fern can be pruned once a year if necessary, just about any time, since they are continuously growing.
As a rule, ferns don't really need pruning. Ferns in nature are generally self-cleaning and will release old fronds as they die. In the garden, occasional removal of dead fronds will improve the appearance of the plant, but it is strictly cosmetic. Where the plants are large and very old, severe pruning can take place to the crown. All the fronds can be removed in late winter or before the first new fiddleheads appear. Prune the stems away from the crown in a circular pattern so you are left with a little dome. This is not only attractive, but it prevents accidental damage to the newest growth which appears at the center of the plant.
Deciduous ferns don't necessarily drop all their fronds when temperatures plummet. They do experience dieback and many of the fronds will fall off or turn brown. From a cosmetic standpoint, it is best to get these dead fronds out of the plant. You will also increase light and room for new leaflets. Many people prune the deciduous ferns in fall so they are ready for the spring, but the old fronds provide protection for the crown. It is best to leave them, unattractive though they may be, until spring.
Pruning Indoor Ferns
Boston, staghorn and maidenhair are some of the common ferns used as houseplants. These plants do not need pruning but they do need cleaning. The difference is that pruning increases the health of a plant and is done for many reasons, while cleaning is just routine maintenance. As with outdoor ferns you may choose to remove dead fronds. These should be cut with very sharp scissors or pruning shears and taken back 1/4 to 1/2 inch above the crown. The only time you would ever need to prune out all the fronds is when you are faced with a monumental pest problem. In this case, fertilize one week before the big haircut and then remove all the fronds.