Boston fern, Nephrolepis exaltata, is one of the most popular ferns to grow as a houseplant indoors. Also known as sword fern, it is an ideal choice for an easy indoor garden.
What is Boston Fern?
Boston fern has been popular as a houseplant since Victorian times. It is native to the Americas but is grown indoors in many regions around the world.
It can also be grown outdoors year-round in USDA zones 9-11 and can be placed outside in summer while temperatures remain above 10-15 degrees Celsius.
The plant is named ‘Boston’ fern because it is said to have been discovered in a fern shipment sent from Philadelphia to Boston in the late 19th Century.
Where to Grow Boston Fern
If you would like to grow Boston fern indoors, the first thing to think about is where it should grow, and the growing conditions that it requires. Key things to think about are light, temperature and humidity, and the growing medium in which the ferns should be placed.
Boston fern should be grown in a location where it receives bright but indirect light. In too shaded a location indoors, these ferns can look a little sparse and weedy. In too sunny a spot, however, where they receive bright, direct sun during the hottest part of the day, they can get scorched.
A spot with an eastern aspect can be ideal since these ferns will enjoy receiving sun in the morning before being somewhat shaded from the sun in the afternoon.
Temperature & Humidity Requirements
Boston ferns naturally grow in relatively warm but not hot, and humid conditions. As when growing other plants indoors, your goal when growing these ferns should be to mimic their natural environment as closely as possible.
These ferns should ideally be grown at temperatures between around 18 and 24 degrees C. They are tolerant of temperatures outside this range to a degree, but will not like extremes, wide, dramatic, or sudden fluctuations.
Temperatures above 35 degrees and below freezing will definitely damage and can kill these plants. But temperatures above 25 and below 10 are strongly detrimental to these plants.
Another very important factor when deciding where to place your fern is humidity. These ferns love a very humid situation and will do best where a humidity of over 80 percent can be maintained.
This means that these ferns thrive in a humid location such as a well-used, bright bathroom, or perhaps a kitchen area close to a frequently used sink. However, when growing indoors, even these rooms are not always humid enough.
So to increase humidity group houseplants together, mist regularly, and place a pebble and water tray below your pots.
Soil/ Growing Medium
For this fern, a growing medium that is rich, fertile, and loamy is a must.
For environmental reasons, you should avoid peat-based compost. But you should choose a good quality peat-free alternative that offers the same moist yet free-draining and mildly acidic environment in which Boston ferns will thrive.
A soil-based peat-free potting mix with added grit for drainage could be ideal. You can make your own from 1 part loam, parts sharp sand, and 3 parts leaf mold.
Planting Boston Fern
Boston ferns can be propagated through the division of mature plants, or grown from spores. However, these plants are commonly purchased in pots from garden centers or plant nurseries, or from online retailers.
Purchased plants should be potted into a chosen container as soon as you get them home or they arrive. A glazed terracotta pot that retains water fairly effectively, but which has good drainage holes at the base to allow excess water to escape will be ideal.
The container that you choose should be large enough to accommodate the existing root system but not too much larger, as too large a container could make it more likely that waterlogging will take place and this can damage your fern.
Carefully place the fern into its new container, firm the growing medium gently around the edges of the existing roots, and water it in well.
Caring for Boston Fern
Boston ferns, when positioned correctly and given the right environmental conditions, are remarkably easy to care for and to grow. This no doubt accounts for their ongoing popularity with houseplant ‘parents’ around the world.
Boston ferns require consistent moisture throughout the year – but more in the summer and much less over the winter months.
Remember when watering that while these ferns like things moist, they also need the conditions to be free-draining and will not thrive in waterlogged conditions. So take care not to overwater and make sure that excess water is always able to drain away freely.
Boston ferns do not typically need feeding as long as they are growing in a reasonably rich and fertile growing medium.
However, when grown indoors in containers, especially if the growth seems poor, they may sometimes benefit from a half-strength organic liquid plant feed every month or so through the spring and summer months. But any feeding, if you choose to feed this fern, should cease before winter arrives.
Pruning is not required for Boston ferns but can be undertaken for aesthetic reasons. It is common to remove any dead fronds that naturally arise from around the edges of the plant, but should you wish you can also trim away other outer leaves as desired.
You should only repot Boston ferns once they become rootbound. And make sure that when you repot, you do so into a pot that is only slightly larger in size than the one that the plant is currently within. Make sure that you place the fern at the same depth that it was in its previous container.
As you repot a Boston fern, you might also consider lifting and dividing the plant to obtain new plants for your houseplant collection, or to avoid increasing pot size if the fern is already quite large. This is the easiest way to propagate Boston ferns.