Fern Turning Brown? (6 Solutions That Actually Work)


Fern turning brown

Ferns turning brown is one of the most common houseplant woes that I encounter. I feel your pain. I love ferns, but I fully acknowledge they can be fussy customers. My own fern had turned brown, so I made it my mission to find out why and how I could save it.

Under the tutelage of some expert growers, I can share with you all the tips and tricks to identify why your fern is turning brown and how you can save it…

The most common reasons fern leaves turn brown are low humidity and underwatering. Ferns prefer 40% humidity, whereas indoors, the humidity is typically around 10%, which causes the leaves to lose water and turn brown and crispy at the tips.

As I discovered there are several reasons that can contribute to your fern turning brown; I decided to summarize the most important points for you in the following table…

Causes:Reason Fern Leaves Turn Brown:
Low humidity.Indoor ferns are all tropical or sub-tropical plants that require a humidity of at least 30% with 40% or more being optimal. Low humidity indoors causes fern leaves to turn brown and crispy.
Underwatering.Ferns should be watered thoroughly and the soil should be consistently moist (but not saturated). Dry soil causes the leaves to turn brown.
Small pots.Smaller pots can dry too quickly after watering and cause the roots to become pot-bound, which can turn the leaves brown.
Too Much Sun.Ferns are native to living under woodland and forest canopy with only filtered light or full shade. Too much can turn the sensitive leaves brown.
High Temperatures.Ferns prefer relatively cool temperatures of between 65°F to 75°F during the day and 10 degrees cooler at night. High temperatures cause the soil and leaves to dry out and turn brown.
Outdoor ferns turning brown in Fall.Outdoor ferns turn brown in the Fall with a dying appearance due to Winter but grow new green leaves in the following Spring.

Keep reading to learn how to identify the cause of your fern turning brown and for my tips on how to save it…

1. Low Humidity (Increase the Humidity to 40%)

How to revive a dying fern
This is a photo of my fern leaves, which turned brown due to low humidity and underwatering.

I discovered that usually, the reason for indoor fern leaves turning brown is because of low humidity.

As we discussed, indoor ferns are native to tropical climates, and they are adapted to living in 40% humidity or more. The humidity indoors is usually too low at 10%, which causes the fern’s leaves to turn brown, dry out, and crispy.

Boston, Maidenhair, Asparagus, Staghorn, and Java ferns are the most common species of houseplant ferns, which are native to tropical regions where the humidity is typically between 40% and 70%.

So, the reason for brown leaves is usually because of this contrast in humidity as the low humidity saps moisture from the fern leaves, turning them brown and crispy as this is contrary to their preferred conditions.

I should highlight there are several factors can exacerbate low humidity in the home and turn ferns brown, such as:

  • Air conditioning. The air circulated by air conditioning not only creates an unfavorable air current but also dries the air and turns the fern leaf tips brown.
  • Forced air. Similar to air conditioning, forced air creates a current of dry air, which lowers humidity and increases the temperature (which also dries out the soil more quickly). Ferns prefer a temperature range of 65°F to 75°F, causing leaves to turn brown and crispy.
  • Sources of heat. Whether it’s forced air, central heating, or a fireplace, sources of heat create convection currents in the house, which causes dry air to circulate and dry out your fern plant.

My own fern gets hit with a double whammy of indoor heating in the winter and air conditioning in the summer. No wonder they turned brown!

However, even without these factors reducing humidity, the average humidity of your home is still likely to be far too low for your fern plant to tolerate.

How to Solve it:

I saved my fern with brown leaves by increasing the humidity by placing my houseplants nearer together to create a humid micro-climate, and located my fern in a more humid room (such as the bathroom),

You can also use a humidifier that can create the exact level of humidity that can prevent your fern from turning brown.

Humidifiers are always my recommendation to reliably save a dying indoor fern, as they can create the optimal humidity for your fern that replicates the fern’s natural environment. With some humidifiers you can precisely set the level of humidity and localize the mist it around your fern.

I love to use humidifiers, and I have great results doing so. The cool thing is you can just set it up and forget about it.

However, another method I have tried is to place your fern on a saucer of water filled with pebbles so that the fern’s pot sits on the pebbles above the water line.

The evaporation from the saucer contributes to a more humid environment throughout the day to counteract dry air.

I must emphasize the importance of keeping the pot above the waterline, which allows excess water to drain freely, as ferns require the soil to be consistently moist but not boggy, as saturated soil can cause root rot.

I personally prefer to use a humidifier as I have found the water pebble tray method less effective.

Misting the fern everyday can also help, however, typically I advise to not do this as if the fern’s leaves are damp from too much misting with a spray bottle, then this can result in foliar disease which is why I recommend placing your fern near to other plants, on a saucer with water and using a humidifier.

Once you have created a more humid environment for your fern, then the higher humidity should prevent more leaves from turning brown.

When I have addressed the humidity problem, I use a sharp pair of pruners or scissors to cut away any dry, brown, crispy leaf blades and leaflets back to healthy growth as the brown growth does not regenerate.

Pruning your fern does stimulate new healthy green growth, and as long as the humidity is consistently at least 30% (ideally 40% for most species), then the fern should stay a healthy green.

A higher relative humidity is the most important factor for the health of your fern.

It was not until the following spring before my fern looked healthy again.

(To learn more, read my article, how to revive a dying fern).

2. Underwatering (Soil Should be Consistently Moist)

Often, the reason for fern leaves turning brown at the tips is because of underwatering. Ferns prefer the soil around the roots to be consistently and evenly moist. If the soil dries out between bouts of watering, then the leaves turn brown, crispy, and dried out because of a lack of moisture.

To understand why our ferns turn brown, it can help if we understand how they grow naturally…

Ferns are all woodland or forest plants that grow in soil that is rich in organic matter, usually composed of leaf mold.

Your ferns have adapted to growing in soil that retains lots of moisture yet has a porous structure that allows excess water to drain away from the roots (preventing root rot).

If you do not water often enough or water too lightly and the soil dries out, then I find brown leaf tips are one of the first signs of stress. However, drought stress can also manifest in the fern browning from the bottom of the plant.

How to Solve it:

You need to water your ferns as often as required so that the soil is evenly and consistently moist. Exactly how often you have to water ferns depends on your climate, the species of fern, and the size of the plant (the larger ferns have more leaves and more surface area from which to lose water).

To test the soil and monitor the moisture levels in the soil, I feel the weight of my fern’s pot by lifting it as it should feel heavy after watering, then gradually lighter as the roots of the fern uptake the moisture in the following days, or if the fern is outdoors you can test the soil to a fingers depth to detect the level of moisture and determine when your fern needs watering.

Always water your fern with a generous soak rather than a light watering.

Water thoroughly so that excess water drains through the drainage holes in the base of the pot.

This ensures that the fern’s soil is consistently and evenly moist around the roots so that they can effectively draw up moisture to transport to the leaves to prevent them from turning brown.

If you water too lightly then then soil the surface of the soil becomes moist and the water does not reach the fern’s roots where it is required.

3. Small Pots Dry out Too Quickly Cause Brown Leaves

This happened to my potted fern. My fern grew rather large after 3 or 4 years (after I used fertilizer) and became too large for its pot. Its extensive root system drew up all the available moisture in its pot super quick, which caused the leaves to turn brown due to drought stress.

I learned that naturally, fern roots have a tenancy to grow wider rather than deeper, so if your fern is in a narrow pot, the roots can become pot-bound much quicker. I find ferns become pot bound before my other houseplants, which is why I think this is such a common problem.

Ferns grow well in pots that are proportionately wide as they are deep or even in somewhat wider, shallow pots, as this can accommodate their shallow, wide root system.

How to Solve it:

Typically, ferns require repotting every 1-2 years, so check periodically to see if the roots are pot-bound by removing some of the topsoil and repotting your fern to a pot that is at least an inch wider in diameter.

I recommend using new potting soil as this provides more nutrients and can hold more moisture than older soil, which may be more decomposed and less able to retain moisture. I personally use miracle grow houseplant compost with great results.

Pro tip: Whilst ferns are ale to grow in a wide range of pots, mine tend to grow better in unglazed clay pots as clay is a porous material that allows the soil to dry out more evenly which creates the optimal balance for ferns (ferns grow in soil that is moist, but not saturated).

A pot that dries out more evenly is far less likely to cause problems relating to root rot, which is more likely to occur in impermeable plastic pots. Also, ensure that the pot has drainage holes in the base to allow excess water to escape after watering.

With a larger pot, the soil can retain more moisture around the roots, and the fern has more access to the moisture and nutrients it requires to prevent the leaves from turning brown and dying back.

As we discussed, just Cut back any brown, crispy, dying leaves with a sharp pair of pruners back to healthy growth (as the individual brown, dying leaves do not regenerate) to help stimulate new green, healthy leaf growth.

4. Too Much Sun (Ferns Grow in Full Shade)

This is a classic mistake I think we have all made with a houseplant at some point!

Ferns grow naturally under a woodland canopy with filtered light or full shade. If the fern is located in too much sun, then this causes the leaves to lose water at a quicker rate, then the roots can draw up moisture, which causes the leaves to turn brown and crispy with a dying appearance.

All ferns are specially adapted to growing in woodland or forest canopy with full shade or some filtered light.

This means your ferns are very sensitive to direct sunlight, which can dry out the soil and leaves too quickly, causing them to turn brown.

I would also keep in mind that too much sunlight is also likely to decrease the humidity and increase the temperature around your fern to an unfavorably high-temperature range, which can all contribute to the fern turning brown and dying back.

How to Solve it:

Always locate your fern in an area with either filtered light or in the shade to keep the fern alive.

Ferns are naturally adapted to the shade, which makes them very versatile houseplants and suited to shadier gardens, so either move your fern to a shadier spot in the garden or a shadier spot in the house.

Almost all indoor ferns that are commercially popular originate from tropical regions, so whilst moving your fern out of direct sunlight is a good start, to save your fern, it is important to:

  • Increase the humidity around the fern, ideally with a plant humidifier and…
  • Water the fern as often as required to keep the soil moist but not saturated.

I have personally had a lot of success growing ferns in my bathroom. The frosted glass creates beautiful filtered light, whilst the natural humidity of the bathroom is appreciated by the leaves.

These are the most effective strategies for saving your fern as it is most likely dehydrated and suffering from a lack of humidity from too much sun.

As I have stated, just snip off any brown leaves or leaflets of your fern if they do not recover to help stimulate new healthy green growth, and I assure you your fern will look good in no time!

5. High Temperatures Cause Fern Leaves to Turn Brown

Indoor ferns turn brown if the temperature is more than 80°F for an extended period.

Ferns prefer a cooler temperature range of 65°F to 75°F. In higher temperatures, the fern can lose more moisture from the leaves; then, it can draw up at the roots, which causes the fern to turn brown with a dying appearance.

Whilst Indoor, houseplant ferns are native to tropical areas, they have quite specific temperature requirements that are slightly on the cool side. Typically, ferns prefer a temperature range of 65°F to 75°F during the day and around 10 degrees cooler at night.

Let’s think why our homes may become too hot for ferns…well if we have the heating come on in the Winter, then the temperature is likely going to increase at night when the fern is expecting it to cool down…

Ferns tend to live in shaded and protected areas of woodland or forest habitat and rarely have direct sunlight which means the temperature is usually relatively cool.

Room temperature is most often defined as 68°F (20°C). However, this can vary greatly depending on your climate and the specific room.

All these factors result in the fern leaves turning brown as a sign of stress. The leaves can also turn dried out and crispy and drop off.

How to Solve it:

Locate your indoor fern in a room with a temperature range of 65°F to 75°F. Typically, the best room for indoor ferns is the bathroom due to its naturally higher humidity and typically cooler or perhaps more consistent temperatures than other rooms of the house.

Ferns prefer a room temperature at night that is around 10 degrees cooler than the day temperature, so the main thing we need to remember is to avoid placing your ferns near any sources of heat or in the air current of forced air.

I must reemphasize the importance of maintaining a humidity of around 40% and watering your fern so that the soil is moist for it to recover from any kind of stress that has turned the leaves brown.

Cut back any brown foliage, as it does not typically recover. Pruning the brown leaves stimulates the growth of new, healthy green leaves.

6. Outdoor Fern Turning Brown (Transplant the Fern)

Outdoor fern turning brown in the Fall.
This is my outdoor fern turning brown in the Fall.

Outdoor ferns turn brown with a dying appearance because of Winter temperatures, dry soil, or too much sun. Ferns require moist soil with lots of organic matter to retain moisture and prefer shade or filtered light.

I should highlight first and foremost that fern leaves turn brown and should be pruned back in Winter, so I can assure you that this does not mean the fern is dying; it is just the typical cycle of outdoor ferns throughout the year.

Ferns also do not tolerate being planted in dry, sandy soil that drains too quickly or in full sunlight, which dries out the fern, turning the leaves brown and crispy.

How to Solve it:

Prune back the leaves at the end of Fall as they start to turn brown as they can no longer photosynthesize.

I always do this as one of my last gardening jobs of the year as this tidies up the appearance of the fern and allows me to cover the fern’s rhizomes (which are underground) with compost mulch to help insulate them over Winter and the fern should grow back healthy the following Spring.

If the soil is sandy and dries out too quickly after watering or rainfall the transplant your fern to and amend the planting area with lots of compost, leaf mold or well rotted manure.

These three materials retain lots of moisture yet have a porous structure that allows excess water to drain away from the roots to prevent root rot.

Always plant ferns in areas of shade or some filtered light, as they cannot tolerate too much direct sunlight. Either transplant the fern to a shadier location or create shade using other plants or shrubs.

Key Takeaways:

  • Fern leaves turn brown because of low humidity and underwatering. Ferns are tropical plants that need humid conditions. The humidity indoors is often too low, which saps moisture from the leaves, causing them to turn brown, crispy, and dry out with a dying appearance.
  • The tips of ferns turn brown due to underwatering. Ferns require the soil to be consistently moist but not saturated. If the soil dries out between bouts of watering, the fern’s leaves turn brown and crispy at the tips due to a lack of moisture around the roots.
  • Smaller pots dry out more quickly. Ferns need consistently moist soil, so if the potting soil dries out, the leaves turn brown and crispy with a dying appearance. Ferns’s root systems tend to be wide and shallow, so the roots quickly become pot-bound in small pots, which can cause the leaves to turn brown.
  • Fern leaves turn brown in too much direct sunlight. Ferns are adapted to living under a woodland canopy with filtered light or full shade. In full sun, the sensitive leaves turn brown and crispy with a dying appearance.
  • Indoor ferns can turn brown if the temperature exceeds 80°F for a long time. Ferns prefer cooler temperatures of 65°F to 75°F. In high temperatures, the fern leaves lose too much moisture, and the soil dries out too quickly for the roots to draw up moisture, which turns the leaves brown and crispy with a dying appearance.
  • Outdoor ferns turn brown with a dying appearance naturally in the Fall before Winter. The fern grows new green leaves the following Spring. Outdoor ferns can also turn brown if the soil is too dry or they are in too much sun. Outdoor ferns require moist soil and shade to prevent the leaves from turning brown.
  • To save ferns with brown leaves, use a humidifier to increase the humidity, water as often as required to keep the coil consistently moist, avoid draughts and indoor heating, place the fern in an area of indirect light, ensure a temperature range of 65°F to 75°F and snip back brown leaves to stimulate the growth of new green leaves.

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