The Victorians loved Boston ferns (Nephrolepisexaltata), and they’re still popular today, especially on Southern porches. Sometimes called sword ferns, Boston ferns reach two to three feet tall and wide and form green or bluish-green fronds that arch gracefully as they grow. Gardeners can enjoy Boston ferns on a porch, grow them outside in dappled shade, or pot them near a window that gets bright, indirect light. With the right care, these plants can thrive for years. Hint: The right amount of moisture in the air and soil are keys to success.
Boston Fern Care
Don’t let the name fool you. Boston ferns aren’t native to the northeastern United States. In their native—tropical regions, humid forests and swamps—they can reach seven feet tall. These perennials can overwinter outside in USDA Zones 10 to 12, but gardeners in cooler climates usually treat them as annuals or bring them indoors in the fall.
These ferns need fast-draining soil with a pH of 5 to 5.5 that’s rich in organic materials. If you’re growing your Boston fern in a container, make sure it has drainage holes, so water won’t stand around the roots and cause rotting.
Cool morning sun is ideal for Boston ferns. They need at least a couple of hours of bright, filtered or indirect light each day. Direct sun can burn them, but they won’t grow in total shade either.
Water regularly to keep their soil evenly moist, or when the top inch of soil feels dry. Outdoor plants often dry out faster than houseplants, so you may need to water in the morning and afternoon. Avoid letting your fern dry out, or it may not recover.
Most homes are too dry for Boston ferns. Give them more humidity by using a room humidifier, keeping their pots on top of pebbles in a tray filled with a little water (don’t let the pots touch the water), or misting often. Keep them away from drafts and vents.
Feed Boston ferns with a balanced houseplant fertilizer in spring and summer following the directions on your product.
To overwinter your fern, move it to a cool, dark place where the temperature doesn’t drop below 55 degrees F., such as a basement. Reduce watering to once a month. In the spring, cut off dead fronds and move the fern back outdoors.
Types of Boston Ferns
Some types of Boston ferns are easier to find than others, but they’re all easy to grow. Hardiness zones can vary, so check the plant tag if your fern will be outdoors when the temperatures drop.
This fern is the classic Boston fern. The light to medium green fronds can grow 4 feet long.
‘Florida Ruffle’ is also a medium-sized plant with feathery-looking leaflets.
‘Golden Boston’ has golden-green fronds and brightens shady nooks or garden spots.
‘Massii’ is darker green than ‘Bostoniensis’ and has a stronger cascading habit.
‘Rita’s Gold’ is compact, with chartreuse to golden fronds.
‘Roosevelt’ has lacy, frilly foliage and long, wide fronds.
A compact, ruffled fern, ‘Dallas’ doesn’t shed as much as other Boston ferns.
‘Teddy Junior’ is a relatively compact fern with light green foliage that is darker.
At less than 12-inches tall, ‘Lemon Buttons’ is perfect for terrariums.
‘Fluffy Ruffles’ is prized for its softly ruffled fronds.
‘Tiger Fern’ has attractive gold and green “striped” leaves.
How to Prune
Little pruning is needed, except to remove fronds that have lost their leaves or died. When you prune, don’t cut at the top. Cut the side fronds or trim around the plant to shape it. Prune in spring or summer, or when you’re repotting.
How to Propagate
You can propagate a Boston Fern by cutting or pulling a runner off the base of the plant. Don’t worry if you don’t get any roots; they’ll develop when you put the runner into a pot of potting mix. Water lightly and cover the pot with a clear plastic bag. Keep it in bright, indirect light where the temperatures are 60 to 70 degrees F. When you see new growth, take off the bag.
You can also divide a Boston fern. Let the plant dry out and then take it out of its pot. Cut the root ball into 1- to 2-inch sections. Clip the roots to 1 ½ to 2-inches long and pot up the sections in fresh potting soil. Keep them evenly moist in a warm, bright spot out of direct sun.
How to Pot or Repot
Spring is the best time to pot or repot a Boston fern. Use a pot with drainage holes that are a little bigger than the root ball. Slide the fern out of its original pot and put it in the new one. Add fresh potting mix to within one inch from the top. Firm down the soil and water thoroughly.
Boston ferns can be plagued by diseases like root rot and powdery mildew. To help prevent these, don’t overwater or let the soil stay soggy.
Dry, curled foliage is usually a sign that the humidity is too low.
Too much sun can scorch Boston ferns and turn the foliage tips brown.
If you spot pests like spider mites, mealybugs, scale, or fungus gnats, quarantine your Boston fern until you can eliminate them. Try knocking them off with a spray of water from your hose shower or spray them with horticultural or Neem oil. Spray weekly until they’re gone.
Too much fertilizer can cause frond tips and edges to turn brown. Flush the soil with lots of water and wait six months to feed again. Repot container-grown ferns in fresh potting mix.