How to Grow a Boston Fern (Sword Fern) Indoors or Outdoors
Boston ferns, the staple of the Victorian parlor, make excellent modern day houseplants. They lend a tropical air to your home without a lot of fuss or bother on your part.
What are Boston Ferns?
Boston ferns (Nephrolepis exaltata) are members of the sword ferns family that are native to tropical areas of the world. Sword ferns have upright fronds. Boston ferns have fronds that arch downwards. The original fern was discovered in a shipment of plants from Philadelphia to Boston in 1894, hence its name Boston fern.
The ferns are hardy in zones 9 – 11. North of zone 9, they are grown as houseplants. They are quite large when grown outdoors, growing to a height of 7 feet. Indoors, they only grow 2 to 3 feet tall. Boston ferns grow best in rich, well-drained soil. Outdoors they prefer full shade or partial shade, while indoors they do best in filtered sunlight. Like other ferns, they do not have flowers nor do they produce seeds. Instead, they reproduce by spores that grow on the undersides of the fronds that are released in the summer.
How to Grow Boston Ferns Outdoors
In growing zones where Boston Ferns are hardy and can be grown outdoors, choose a shady or semi-shady spot in your yard for them. Their natural habitat is very humid so be sure to choose a sheltered spot where they are less exposed to drying winds. They grow best in rich, well-drained humus soil. The plants need to be fertilized. Use a balanced slow release fertilizer to prevent over-fertilizing. Ferns that have been fed too much fertilizer will develop brown ends to their fronds.
In the landscape, Boston ferns are often planted in groups or around the base of shrubs or trees.
How to Grow Boston Ferns Indoors
Most of us grow our Boston ferns indoors, only putting them outdoors during the summer. Their preferred temperature range is 60⁰F - 75⁰F so refrain from moving your plant outdoors until the night time temperatures reach 60⁰F. In the fall, move it back indoors when the night temperatures start to fall below 60⁰F. Place them in a shady or semi-shady spot in your yard.
Indoors Boston ferns need filtered sunlight rather than the shade they prefer outdoors. An east facing window is ideal because the plants will only get morning sun. The rest of the day they will be in the shade. If you only have west or south facing windows, hang a sheer curtain in the window to cut down on the amount of sun your plant receives.
Humidity is also critical. Our homes are much dryer than their natural environment. Be sure to place your plant well away from heating and air conditioning ducts which will blow dry air on them. Bathrooms and kitchens, which are more humid than the other rooms of our homes, are great places for Boston ferns.
You should plan on providing extra humidity for your plant. You can mist it regularly. Or you can construct a humidity tray which is simply a gravel filled tray that is filled with water. The plant is placed on top of the gravel. As the water evaporates from the gravel, it provides humidity for the plant. You will need to refill your humidity tray regularly.
Use well-drained potting soil and keep it moist but not soggy. Soil that is too wet will cause root rot.
You will need to fertilize. A balanced slow release fertilizer is the easiest way to fertilize your plant. If you prefer liquid fertilizer, add it full-strength on a monthly basis. You can also dilute the fertilizer and apply it every other month instead. You will know if you are over-feeding your fern because it will start to develop brown tips on the ends of its fronds.
Thanks to their arching fronds, Boston ferns are stunning when displayed on pedestals or in hanging baskets.
How to Divide Boston Ferns
Boston ferns are propagated by division. Dividing them is easy. Simply lift the plant out of it pot. Using a sharp knife, cut the root ball into four pieces making sure that each piece has fronds. Then repot the divisions into separate pots.
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