Fern care 101. How to care for your ferns

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A guide to house-ferns

The soft, delicate appearance of fern brings a surge of green vitality to any place where you want a tropical touch. And, although ferns are not difficult to grow, most of them do need higher levels of humidity than humans consider comfortable. Indeed, once-popular ferns such as the maidenhairs ferns are seldom seen in homes and offices today because of their need for very moist air.

Maidenhairs ferns are seldom seen in homes and offices today because of their need for very moist air
Maidenhairs ferns are seldom seen in homes and offices today because of their need for very moist air

The ferns profiled in here are happy with moderate levels of humidity, which can be achieved by misting the plants once a day (or less frequently), double-potting them with sphagnum moss, or setting them on a tray of damp pebbles.

Sphagnum moss
Shiny green bog plants (sphagnum moss) in spring as a nature pattern.
Double-potting ferns with sphagnum moss
Double-potting ferns with sphagnum moss
Setting ferns on a tray of damp pebbles to increase level of humidity
Setting ferns on a tray of damp pebbles to increase level of humidity

These and other techniques for raising the humidity level around plants. Today’s roomy bathrooms are ideal spots for small ferns, which love to be bathed in steam each time you shower. You can also grow small ferns in a terrarium.

Roomy bathroom is the perfect spots for small ferns
Roomy bathroom is the perfect spots for small ferns
Small ferns can be grown in terrarium
Small ferns can be grown in terrarium

Exactly how attentive you must be to the matter of humidity depends on whether a fern has thin, feathery leaves or thick, leathery ones. The thinner the leaves, the more essential high humidity becomes. This is why holly ferns, bird’s nest ferns, and brake ferns often succeed in the same place that a feathery asparagus fern sheds into a withered mess.

Holly ferns
Holly ferns
Bird’s nest ferns
Bird’s nest ferns
Brake ferns
Brake ferns
Feathery asparagus fern
Feathery asparagus fern

Begin with an easy fern before moving on to the more demanding ones.

Putting Together a terrarium with Ferns – Garden Answer

Caring for fern

Ferns have shallow, fibrous roots that quickly fill the surface soil in containers. Pots should be as wide as they are deep. Clay pots darken a shade when they are well dampened, so they make good containers that double as moisture indicators. Ferns with attractive surface roots, such as squirrel’s foot ferns or hare’s foot ferns (or rabbit’s foot ferns), are ideal plants for moss-lined hanging baskets.

Squirrel’s foot ferns or hare’s foot ferns (or rabbit's foot ferns), are ideal plants for moss-lined hanging baskets.
Squirrel’s foot ferns or hare’s foot ferns (or rabbit’s foot ferns), are ideal plants for moss-lined hanging baskets.

Light requirement for ferns

The natural habitat of most ferns is the shady forest floor, though some grow in the crotches of tree limbs in damp forests or jungles. All grow best in moderate light and are easily burned by full sun. Indoors, near a north window, is the first place to try placing a fern in summer. In winter, move the plant to an east window if you have one. Offices lit by fluorescent lights are usually bright enough for ferns. If your office is dim, a fern placed on a pedestal, lit with an energy-saving fluorescent bulb, will become a dramatic focal point.

The natural habitat of most ferns is the shady forest floor
The natural habitat of most ferns is the shady forest floor

Some ferns, especially Boston ferns, respond well to being moved to a shady spot outdoors in the summer. In any season, do not move ferns more often than necessary, because they often react poorly to a change of location. If a fern is doing well where it is, limit its movement to rotating it a quarter turn every few days to make sure that all sides get exposed to directional light.

Temperature

Despite their tropical demeanor, most indoor ferns grow best in normal or cool room temperatures. A temperature difference of about 10°F/3°C between day and night is beneficial since this mimics the conditions they might enjoy in the wild. Slight chilling of ferns, to about 50°F/10°C, is much less stressful than overheating. Dry heat is a fern’s worst enemy.

Dry heat is a fern’s worst enemy
Dry heat is a fern’s worst enemy

Fertilizer for ferns

Ferns are not heavy feeders, but they do need a little plant food to support new growth. From mid-spring through summer, feed ferns with a balanced houseplant food mixed at half the rate given on the package. How often you feed a fern depends on the season, the species, and the age and vigor of the plant. Monthly feedings may be sufficient, but ferns that show strong seasonal growth in early summer will benefit from more frequent doses of fertilizer. Feed ferns less often in winter. Suspend feeding of ferns for a few weeks after dividing them, or after a repotting operation that involves pruning the roots. Resume feeding after a 6-week recovery period. This break gives new or damaged roots time to develop protective outer layers, which reduces the risk of chemical burning from fertilizer.

Ferns care: Watering

Water ferns lightly yet often. Overwatering can cause roots to rot, while underwatered ferns will not grow and may wilt. In summer, it’s a good practice to check ferns daily, though you may need to add water only every other day. In winter, check ferns twice a week. Keep a small pump spray bottle filled with water near your ferns, and mist them each time you check the soil’s moisture. Dribble a little water from the bottle into the containers whenever they seem dry. Room-temperature water is best for misting and watering ferns.

Keep a small pump spray bottle filled with water near your ferns, and mist them each time you check the soil’s moisture
Keep a small pump spray bottle filled with water near your ferns, and mist them each time you check the soil’s moisture

If a fern dries out too much, the peat moss in the soil mixture — combined with a tight mass of surface roots — may make it difficult to reestablish even moisture in the container. To rehydrate a very dry fern, fill a tub or sink with room-temperature water and submerge the pot to just over the rim. Hold the pot in the water for about 2 minutes, until bubbles stop floating to the surface. Remove the pot and allow it to drain until it stops dripping. Never leave a fern sitting in standing water for more than a few minutes.

Best Soil to plant fern

When planting ferns, amend packaged potting soil with peat moss. A half-and-half mixture of potting soil and pulverized peat moss is perfect for most ferns. Dry peat moss absorbs a lot of water, so it’s best to mix the potting soil and peat moss together in a pail and dampen it well before using the mixture to pot up a fern. Do not use potting soil that contains fertilizer. Fertilizer that dissolves too fast can burn delicate fern roots.

A half-and-half mixture of potting soil and pulverized peat moss is perfect for most ferns
A half-and-half mixture of potting soil and pulverized peat moss is perfect for most ferns

Repotting your ferns

Like most plants, ferns develop more new growth in summer than in winter, so spring is the best season to repot them. If you want to encourage a small fern to grow larger, move it to a slightly larger pot when the roots have filled the container. To control the size of large ferns, remove the plant from the container and use sharp scissors to prune off about a quarter of the roots. Then replant it in the same size container it grew in before. Except for big Boston ferns, there is seldom a need to use a pot more than 8 in/20 cm wide.

When repotting any fern, take a moment to check the health of the roots. Healthy fern roots have light brown to whitish growing tips. If the roots are black, they are dead. Trimming away dead roots will help protect the health of those that remain by limiting the number of fungi, which regard struggling roots as a delicious lunch.

Fern propagation

Some ferns, such as Boston ferns, multiply by sending out shallow roots, which develop buds that grow into new plants. These ferns can be propagated by division.

Some ferns, such as Boston ferns, multiply by sending out shallow roots, which develop buds that grow into new plants
Some ferns, such as Boston ferns, multiply by sending out shallow roots, which develop buds that grow into new plants

Use a sharp knife to cut away little plants that grow near the edge of the container, with roots attached; promptly pot them up, and then refill the hole left behind with a mixture of potting soil and peat moss. Alternatively, in spring when new fronds begin to unfurl, remove the entire plant from the pot and use a sturdy serrated knife to cut the root mass into two or three chunks. Also, cut back old fronds and discard them. Repot the divisions and be patient as they slowly recover from surgery.

Fern propagation
Fern propagation

Ferns that develop furry creeping rhizomes, such as Davallia and Polyodiumspecies, can be propagated by severing surface roots and planting them in a fresh container. Use a piece of wire or a bent-out paper clip to pin them securely on the surface of the potting mixture. To maintain high humidity while the rhizomes develop roots, enclose the container in a translucent plastic bag until tiny new fronds appear.

Most other ferns reproduce by sporulation, an ancient reproductive process that evolved 200 million years ago when Earth was a world of water. You will often see round to oblong brown spore cases arranged symmetrically on the undersides of fern fronds in spring and summer. These structures contain single-celled spores, which are the size of dust particles. Unlike seeds, spores contain no food reserves. If they fall onto a very moist medium, they divide into specialized cells that become eggs and sperm. A watery environment is needed for the sperm to unite with the eggs, but if fertilization is successful, the fertilized zygote grows into a new fern. Depending on the species, the transition from spore to a new plant may take weeks or months, so it is a difficult process to manage indoors. However, it may occur quite spontaneously in a humid terrarium. Should you see a greenish mass growing on the soil’s surface beneath a fern in your terrarium, it may be evidence of spores that have successfully reached their sexual stage. Continue to watch, but do not attempt to transplant baby ferns until the little fronds are at least 1–2 in/2.5–5 cm tall.

Final notes

Chemically speaking, ferns are delicate plants. Never use any type of leaf shine product on ferns, because they can cause severe damage. Ferns are sensitive to pesticides, too, so it’s best to control any pests by removing them by hand or by rinsing the plants in a gentle shower. Tobacco smoke can harm ferns, as can other chemical air pollutants. Ferns that show excellent health are a welcome indicator of clean, uncontaminated air.


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