Growing and caring for Ferns as houseplants, the complete guide
When I imagine ferns, I see big, bushy, and beautiful baskets of Boston ferns adorning the porches of homes during the summer. Either hanging from the porch ceilings or resting upon pedestals. Always a lovely sight. Yes, I tried this approach. However, it wasn’t until a year ago that I first brought a fern from the outdoors to the indoors. Further, it is only in the past three years that I developed an interest in ferns as houseplants. My interest peaked when I noticed an unusual plant growing in my daughter’s apartment. It was a Bird’s Nest fern.
In this post, I share the complete guide to growing and caring for ferns as houseplants. While there are wonderful varieties of ferns for use in the outdoor landscape, this post will focus on growing ferns as indoor houseplants.
Estimated reading time: 12 minutes
Background of ferns
Ferns are one of the oldest species of vascular plants dating back millions of years. In addition, they are second only to flowering plants as the most diverse. Ferns are unique in that they do not form seeds or flowers, instead reproducing via spores. These spores are usually found on the underside of leaves (fronds). Have you ever noticed small dark dots on the underside of fern leaves? These are the spores. However, most gardeners propagate ferns via root divisions as opposed to spores (see the section below on propagation).
When choosing a fern, choose based upon the needs of the plant and the conditions in your home. Always inspect plants before you purchase. Check the top and underside of the leaves. Look for any insects or diseases that may be present.
Characteristics of ferns
The leaves of a fern are called a frond. These fronds are attached to rhizomes (horizontal underground stem) via a stalk called a stipe. What I really love about ferns is when the frond develops a bud. These buds develop in the center of the plant and slowly unfurl and develop into a full-grown leaf. For me, it’s simply a fascinating process to watch.
Caring for your Fern
In this section, I will review the most important care aspects: light, soil, water, fertilizer, transplanting propagating, and potential problems.
Light
While ferns grown outside do well in shade, when ferns are brought indoors, they prefer moderate indirect sunlight. Direct sun exposure can burn their leaves turning them brown. For south and west-facing windows, place ferns a few feet from the window. Direct sunlight from an east-facing window is best. In addition, fern like a daytime temperature between 65 and 75 degrees. In the evening, 10 degrees cooler is best.
Soil
Ferns are not too fussy about soil. A general-purpose indoor potting soil can be used that contains a good amount of organic matter such as peat moss. I like adding between 25-30% perlite to indoor potting soil. This helps with drainage and moisture retention. If you purchase soil, ensure that it is pest-free when you open (should smell earthy), otherwise, return. To understand the soil composition, check the ‘ingredients’ on the back of the soil package. Some potting soils have slow-release fertilizer and/or water retention crystals. This is important for both watering and fertilization considerations.
Water
Before we get to watering, let’s discuss containers because there is a correlation. It is important to plant your fern in a container that has drainage holes and a removable bottom saucer. Clay containers will dry out quicker than plastic due to the porous nature of the clay. Containers should be large enough to accommodate the roots and have an extra inch all around for growth. As with most plants, watering practices are the key to healthy plants.
Many varieties of ferns require a lot of moisture, especially during the growing season. Ferns should be watered when the soil is dry. The question is how to determine when to water. There are two practices I recommend. First, look at the soil. Dry soil becomes lighter in color and may pull away from the sides of the container. Second, stick your finger approximately 2-inches into the soil. If the soil looks and feels dry, then water. Here are a few other watering considerations:
Use lukewarm or room temperature tap water. Rainwater can also be used. Water that has been treated by a water softener should not be used because it contains high amounts of salt.
Water during the day as opposed to at night to ensure that any water on the leaves has time to evaporate.
When watering, water thoroughly. Allow water to run into the saucer and then dump what remains in the saucer after a few minutes.
Houseplants have a period when growth slows. For me in USDA gardening zone 6a, that occurs during the fall and winter. When growth slows, water plants less.
Humidity
High humidity is a key need of most ferns as they do best with 40-50 percent humidity. Here are a few ways to provide your fern with the necessary humidity.
Spritz the plant regularly. While there is some concern that water on the leaves could lead to disease, I have not found this to be the case. I usually spritz a few times per week and just 3-4 spritzes. Also, where you home is located will dictate whether extra humidity is necessary. At our home near the beach in Florida, the humidity is so high that conditions are perfect for fern growing indoors.
Purchase an in-home humidifier. If you home is dry, this will benefit both you and the plant.
Double pot the plant. Place your potted fern inside a larger container. Next, line the space between the two containers with sphagnum moss and then moisten the sphagnum moss.
Place a layer of stone pebbles or gravel in the saucer and then place the container on top of these pebbles/gravel. Keep the pebbles/gravel wet with water but not above the height of the pebbles/gravel. Also, it’s important to periodically (once every three months) clean the pebbles/gravel to avoid algae buildup.
Lastly, grouping plants together will increase humidity. Just ensure that there is sufficient air circulation.
Fertilization
Ferns have modest fertilization needs. Always read and follow the directions on any fertilizer you purchase. Here are a few considerations when choosing a fertilizer:
Every fertilizer will have a series of numbers such as 5-5-5 or 3-2-1 on the label. These numbers indicate the percentage of nitrogen, phosphorus, and potassium (N-P-K) contained within the fertilizer. I use a diluted fish emulsion fertilizer (3-2-1) which comes as a liquid concentrate. Diluted means using half the recommended amount. During the growing season, I fertilize every three to four weeks.
Fertilizers can take the form of either liquid, granular, or slow release.
Like watering requirements, fertilizer requirements decrease when plant growth slows from late fall through early spring. During the active growing season, fertilize monthly with a half strength fertilizer. From September through April, withhold fertilizer.
A newly purchased potted fern may already have fertilizer in the soil. Because this is difficult to know when purchasing, one option is to transplant into your own mixture. Let the plant acclimate to its new environment for a week before transplanting. Remember to check the ingredients on the soil you purchase. Today, many commercial soil mixes contain slow-release fertilizers within the mix. If fertilizer is already included within the mix, then you don’t need to add any incremental fertilizer.
Transplanting
Because ferns like lots of space, transplant your fern every one to two years. Transplant yearly during the first three years and then every other year. When transplanting, only go up one size in a container. For example, if your plant is in a 6-inch diameter container, the next size should be an 8-inch container. For indoor ferns, transplanting can occur in any season.
Here are the steps I follow when transplanting:
Prepare a new container with soil. Start by filling the container with a layer of gravel. Next, fill one-third full of moistened soil. If the potting soil does not contain fertilizer, add a pelleted slow-release fertilizer to the soil (follow directions on the fertilizer label). Set aside.
Water the plant in its original container and then gently remove from the container. Grab the base of the plant and turn the container upside down to release the plant from the container.
Remove as much of the soil from the roots of the fern. If the plant is pot bound, this may be difficult. Just be gentle and keep working around the roots. Eventually the soil will release. It’s best to work over a container that catches the old soil.
Check the roots for any dead pieces and remove.
Set the fern plant into the new container.
Add potting soil evenly around the plant until the soil is one inch from the top of the container. Gently compress the soil around the base of the fern as it is added.
Water the plant.
Place the transplanted fern back in its location.
It may take a few days for the leaves to perk back up, that’s normal.
Propagation
Ferns are propagated via root division, and this is best done during transplanting. Here is the process:
Follow the directions above for transplanting. Remove the plant from its original container.
Using a sharp knife, cut the root ball either in half or in quarters.
Pull each half or quarter apart and plant in a new container (following directions under transplanting).
Water thoroughly
During the first few weeks, create a humid environment by misting every day.
Common Problems
While there can be a few common problems with fern plants, these problems are usually not extensive:
Root rot from too frequent watering. If this occurs, the fern plant may need to be separated and the roots that are good transplanted.
Tips of the leaves turning brown from one of the following possible causes. The brown tips can be trimmed with a pair of scissors.
not enough water (check watering guidelines above)
too much fluoride in the water or fertilizer (switch to rainwater or distilled water and/or check the ingredients in the fertilizer)
too much soluble salts in the water (switch to rainwater or distilled water)
Small brown scale insects or mealy bugs. Dip a cotton swab in alcohol and wipe off.
My favorite varieties of indoor fern plants
Bird’s Nest Fern (Asplenium nidus)
This is a slow-growing epiphytic fern that can be grown outdoors in USDA garden zones 10-11. Epiphytic refers to a plant that grows on another plant and takes its nutrients directly from the air and rain, also called an air plant. However, these are also beautiful plants to grow indoors. Its leaves are light green and crinkled. While it prefers a bright area in the home, it can also tolerate lower light conditions. I love to watch as the leaves unfurl as they grow from the center of the plant. If you look closely at the center of the picture above, you will see one new leaf that is almost fully unfurled.
These plants like their soil evenly moist and benefit from humidity. To add humidity to a plant, put some small pebbles in the saucer under the plant and add water. Set the container on top of the pebbles. Ok, maybe the bird’s nest fern requires a bit more care, but still a great indoor plant to consider.
Boston Fern(Nephrolepis)
Boston ferns first became popular in Victorian times and are still popular today. Perfect in hanging baskets due to their delicate sword-like fronds that arch downward. The fronds on these ferns can grow up to 3 feet long and 6 inches wide depending upon the variety. Boston ferns must be kept moist with high humidity, or the leaves can turn brown and drop. A north-facing window will provide the ideal light for these ferns.
Sometimes, Boston ferns will develop what looks like fuzzy strands growing from the soil. These are called stolon and can be used to propagate new plants. However, an easier and quicker method to a more mature Boston fern is by root division (see Propagation above). If you don’t like the look of these strands, then can either be cut at the base of the soil or pulled out.
Silver Ribbon Fern (Pteris ensiformis)
How lovely is this fern? The stunning silvery-green fronds are just beautiful. The more bright but indirect sunlight these plants receive, the more intense will be the color of the fronds. As with most ferns, keep the soil moist and aim for high humidity. Silver Ribbon can grow up to 2.5 feet tall.
There you have it, the complete guide to growing and caring for ferns as houseplants. As with most plants, the key to success is good light, good soil, and proper watering and fertilization. I hope your fern plants bring you as much joy as mine bring me.
