Yes, a Bird's Nest Fern (Asplenium nidus) can be grown outdoors in parts of the USA, but its survival and prosperity are entirely dependent on replicating its preferred natural environment. This is not a fern for all climates, and understanding its native habitat is key to success.
To understand its outdoor potential, we must first look to its origins. The Bird's Nest Fern is an epiphytic plant, meaning it naturally grows on other structures like trees or rocks in the understory of tropical and subtropical rainforests. It is not a terrestrial plant that roots deeply in soil. Its core needs are defined by this habitat: consistently warm temperatures, very high humidity, bright but filtered (indirect) light, and excellent air circulation around its roots. It is highly sensitive to cold, direct sun, and dry air.
The most significant limiting factor for growing a Bird's Nest Fern outdoors year-round is temperature. It is only cold hardy in USDA Plant Hardiness Zones 10 through 12. This means it can only tolerate average annual minimum temperatures of 30°F (-1°C) to 60°F (16°C). In practice, even a brief dip near or below freezing will cause severe damage or kill the plant. Therefore, it can only be planted in the ground permanently in the most temperate regions of the USA, such as southern Florida, the very southern tips of Texas and California, and Hawaii.
For gardeners within the appropriate hardiness zones, or for those wishing to move potted ferns outside during the warm summer months, placement is critical. The plant must be situated in a location that mimics its native dappled sunlight. Deep shade will cause it to grow poorly, but direct, harsh afternoon sun will quickly scorch and yellow its delicate fronds. An ideal spot is under the high, filtered canopy of large trees like oaks or pines. It also thrives on a shaded north or east-facing patio or porch where it is protected from the intense midday and afternoon sun.
As an epiphyte, the Bird's Nest Fern requires a very well-draining, porous, and acidic growing medium. If planted in the ground, the native soil must be heavily amended with orchid bark, coco coir, leaf litter, and perlite to prevent waterlogging around the crown (the central rosette), which will lead to fatal rot. Watering should be consistent, keeping the medium lightly moist but never soggy. Humidity is paramount. Outdoor areas with natural humidity, often near water features or in densely planted gardens, are best. In drier climates, regular misting or grouping with other plants may be necessary to raise the local humidity level.
For the vast majority of the USA that experiences winter freezes, the Bird's Nest Fern can still enjoy the outdoors on a seasonal basis. It excels as a container plant. Once nighttime temperatures are consistently above 60°F (15°C) in the spring, the pot can be moved to a fully shaded outdoor location. This provides the plant with excellent air circulation and ideal light levels during the peak growing season. It must be brought back indoors well before the first autumn frost to protect it from the cold.
