During the winter when the plant isn’t growing, you can reduce watering, but your fern should never be allowed to completely dry out. Make sure to maintain a balance of elements for best results—as is true for most plants, growing ferns is all about moderation and a sober approach that doesn’t overemphasize any one element.
The Boston fern needs bright indirect light when grown indoors (outdoors, it prefers denser shade). Some species of the Nephrolepis genus can be trained to handle almost full sun, but most species, including the N. extensis ‘Bostoniensis’ cultivar, prefer filtered, dappled light.
Boston ferns need a loamy, rich, organic mixture as a potting soil. Make sure the drainage is good to avoid rotting the roots, which will be evident if the plant is beginning to lose leaves or appears waterlogged. It’s a good idea to choose a soil that contains some organic material.
It is important to keep the root ball moist at all times. If your Boston fern is sitting in a somewhat dry area (instead of humid), mist with water frequently to keep moist.
Temperature and Humidity
These ferns can survive the occasional blast of cold, down to 50 degrees Fahrenheit or even slightly colder for a few hours. However, they really thrive between 60 and 75 degrees. Boston fern grown indoors prefers humidity no lower than 80 percent; in environments drier than this, it should be frequently misted.
During the growing season, feed the fern with liquid or slow-release pellets. If you’re not happy with the fern’s progress, it won’t hurt to slightly increase the fertilizer within reasonable limits.