Boston fern (Nephrolepsis exaltata), also known as sword fern, is an evergreen plant grown for its large, ornamental fronds, compact growth habit and ease of cultivation indoors. The plant typically reaches about 5 feet high when grown in a container, creating a bold display of foliage. Boston fern, native to Florida, requires a warm, humid climate to thrive. Gardeners in the United States usually treat the fern as a houseplant to more easily replicate its natural environment and provide optimal growing conditions.
Keep Boston fern in a location that receives four to six hours of bright, indirect sunlight each day. Maintain a consistent temperature of 60 to 70 degrees F at all times. Do not expose ferns to temperatures below 50 or above 75, or permanent damage could occur.
Mist one to two times per day with a spray bottle filled with lukewarm water to keep the foliage dust free and increase the relative humidity around the plant. Use distilled or rain water if possible; Boston fern fronds are sensitive to the impurities in tap water.
Water Boston fern once every seven to 10 days, allowing the soil to dry slightly between each application. Apply lukewarm water directly to the soil to avoid shocking the plant. Apply until water seeps from the bottom of the container, then remove any excess to prevent rotting.
Feed once every four to six weeks during spring, summer and fall using an all-purpose 10-10-10 NPK fertilizer. Apply at 1/4 the rate recommended by the manufacturer's instructions to prevent overfertilization. Water the fern lightly after applying to prevent injuring the roots.
Prune Boston fern once per year during late winter just before active growth resumes. Remove all damaged, diseased or overgrown fronds by severing them at soil level. New growth will replace the removed fronds shortly after.
Re-pot Boston fern once every two to three years, or whenever the plant becomes crowded in its current container. Increase the size of the new container by at least 4 inches in diameter to allow plenty of room for new root growth. Use a well-drained, moist, fertile potting soil as the growing medium.