Since all ferns are nonflowering foliage plants, lush growth is desirable. A fertilizer that encourages lushness is one in which there is a higher proportion of nitrogen than of phosphate and potash ( high acid, such as for rhododendrons). It is also best to use a liquid type. But all doses should normally be only at half strength. Full strength applications of nitrogen-rich fertilizers can cause root burn in many ferns (esecially if bottom watering).

Feeding frequency depends on the type of mixture in which the plant is potted. An actively growing fern in a soiless, peat-based potting mixture will do best if fed every two weeks. For a fern in a soil-based mixture monthly feedings are enough because ther are natural nutrients in the soil. During periods of slow growth, intervals between feedings should be longer, and fully resting plants should not be fed at all.

There are foliar fertilizers available and occasional spritzes is advisable. These need not be at regular intervals. From time to time simple add some foliar feed to the water used for spritzing your ferns.