How to Care for Boston Ferns Outdoors
Boston ferns (Nephrolepis exaltata), sometimes called sword ferns, have bright green fronds that grow up to 3 feet long and 6 inches wide. The fronds have serrated edges and a rough texture. They are shade-lovers and grow best in soil that is very rich and lightly moist. Boston ferns are hardy in U.S. Department of Agriculture zones 8B through 11 and can be planted outdoors during any season. Frost will kill the foliage during winter, but new fronds emerge from the center of the plant once temperatures warm in spring.
Use a garden fork to loosen the soil 10 to 12 inches deep. Amend with 2 to 3 inches of organic compost.
Dig a hole the same depth and 2 to 3 inches wider than the fern's root system. Place the roots into the soil at the same level they were growing before. Backfill with the loosened soil and water until it is well-moistened, but not soggy.
Check the soil regularly and water whenever the top inch is dry.
Feed once each month, from spring until fall, with houseplant fertilizer.
Clip off damaged fronds as necessary.
Divide every two to three years in early spring.
Boston Ferns Like To Be Crowded?
Begin to think about repotting Boston fern when it completely fills the pot it's growing in. If offsets are growing from the drainage holes or over the sides of the pot, and roots crowd out the potting mix, repotting is overdue. It's better to repot frequently rather than moving the fern into too large a pot. Given free root run in an outdoor bed, Boston fern can grow quickly and become crowded. It spreads by sending out runners and can become invasive. You can contain its growth by installing metal or plastic edging around the garden bed. Water each plant thoroughly.
Boston ferns can be planted under trees and shrubs or used as a ground cover.