The most common reasons for fern leaves turning brown are because of 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.
The Most Common Reasons for Ferns Turning Brown:
|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 why your fern is turning brown and how to implement the solutions to save your fern with brown, dying, crispy, dried-out leaves…
1. Low Humidity (Increase the Humidity to 40%)
Usually, the reason for indoor fern leaves turning brown is because of low humidity. 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, dried 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% to 70%.
The reason for brown leaves is usually because of this contrast in humidity as the low humidity saps moisture from the ferns leaves turning them brown and crispy as this is contrary to their preferred conditions.
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, increases the temperature (which also dries out the soil more quickly and Ferns prefer a temperature range of 65°F to 75°F and 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.
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:
To save a fern with brown leaves increase the humidity by placing your houseplants nearer together to create a humid micro-climate or locate your fern in a more humid room, such as the bathroom, and use a humidifier that can create the exact level of humidity that can prevent your fern 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.
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.
However, 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.
Misting the fern everyday can also help, however 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.
Use a sharp pair of pruner 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.
(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.
Ferns are all woodland or forest plants that grow in soil that is rich in organic matter, usually composed of leaf mold.
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 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:
Water 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 you can feel the weight of the 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
Fern leaves can turn brown if their pot is too small and the roots are pot-bound. Small pots dry out much quicker as they contain less soil, therefore they can hold less moisture. Small pots dry out too quickly from the fern’s roots to draw up moisture which results in brown leaves.
If a fern has been in the pot for too long then the roots can exhaust the potting soil of nutrients and the root system can grow so extensive and require more water than the soil can hold.
It is also important to note 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.
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 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.
Use 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.
Whilst ferns are ale to grow in a wide range of pots, they 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 are 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, the fern has more access to the moisture and nutrients it requires to prevent the leaves from turning brown and dying back.
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)
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 they are very sensitive to direct sunlight which can dry out the soil and leaves too quickly causing them to turn brown.
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 a 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.
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.
Snip off any brown leaves or leaflets of your fern if they do not recover, to help stimulate new healthy green growth.
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.
This is because 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.
High temperatures are most often a problem in the cold Winter months when indoor heating is turned on and temperatures in the evening can increase substantially. These large temperature fluctuations cause the fern stress.
High temperatures increase the rate at which a fern transpires (loses moisture) from the leaves and increase the rate of evaporation from the soil. It is also at odds with its natural conditions to experience temperature fluctuations and high temperatures in the evening when it typically gets cooler in its native forest habitat.
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 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 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)
The reason outdoor ferns turn brown with a dying appearance is because of Winter temperatures, dry soil, or too much sun. Ferns require moist soil composed of lots of organic matter to retain moisture and prefer shade or filtered light.
Fern leaves turn brown and should be pruned back in Winter. 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. This tidies up the appearance of the fern and allows you to cover the fern’s rhizomes (which are underground) with a 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.
- 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 dried 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 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.