Why Is My Boston Fern Turning Yellow? (Causes+How To Fix)

Boston ferns are beautiful plants that thrive in indoor and outdoor gardens. Too often, though, they face challenges that make their leaves turn yellow.

The primary causes of yellow leaves in Boston fern are incorrect watering and low humidity. If your Boston fern turns yellow, check on the soil and make sure it’s moist but not soggy or dry. To fix the issue, increase the humidity around the plant and water the plant before the soil gets dry.

It is natural for the old leaves to turn yellow, but when more than a few leaves show yellowing simultaneously, it is likely to indicate a problem.

In this article, I will discuss the different problems that make your Boston fern yellow and suggest solutions to prevent the problem.

Why my Boston fern leaves are turning yellow?

It is normal for a few old leaves to turn yellow as they age and fall off.

However, if you notice a lot of leaves, including the younger ones, turning pale and yellow, it is time you evaluate the problem.

The yellowing of leaves is caused due to decreasing levels of chlorophyll.

A reduced level of chlorophyll will affect photosynthesis, further affecting the growth.

Multiple reasons lead to the yellowing of the leaves in Boston ferns.

If you do not cure it at the initial stage, this might lead to a serious problem and kill the plant.

Let us discuss the various reasons that lead to the yellowing of the Boston fern leaves.

Inappropriate watering

Boston ferns require evenly moist soil.

They cannot be too soggy or too dry.

A common issue with Boston fern care is an incorrect watering schedule. 

Either you overwater them, or you underwater them.

These reasons can cause the fronds to turn light green in the initial stages and then yellow and wilt.

Though they love moisture, if the soil becomes soggy and waterlogged for a long period, it will cause the leaves to turn yellow.

If not corrected, it can lead to diseases that kill the plant.

Similarly, underwatering can dehydrate your plant and affect its growth.

Due to this, the plant tends to lose its moisture content.

Therefore, you must choose suitable soil for your fern.

If the soil holds a lot of water and moisture, it will lead to root rot.

Also, watch the watering schedule.

Do not water until the top 2 inches of the soil is dry.

Always use pots with drainage holes to run out the extra water, and it does not stay in the pot.

Also read: How To Water Boston Fern? (How Often, How Much & More)

Fluctuating temperatures

Sometimes Boston ferns start turning yellow when there is a lot of fluctuation in the temperature.

They are native to tropical regions, so they cannot withstand extremely cold temperatures.

Low temperatures can cause the reduction of chemical reactions that the plant performs.

Similarly, though they come from tropical areas, they cannot tolerate a lot of heat.

Extremely hot summers can dehydrate the leaves and turn them yellow.

Ideally, the temperature should be between 60°F-75°F. 

Temperature higher or lower than this range can cause various problems, including yellow leaves.

Place the Boston fern in a position where the plant doesn’t face extreme high or extremely low temperature and is away from the cold vents, heater, air conditioners, and other appliances.

Fluctuation in temperature at these positions can dry up the leaves and make them yellow.

Humidity levels

Boston ferns thrive on humidity levels above 80%.

Any amount of low humidity can severely affect the health of this plant. 

They start to turn yellow if the humidity in the air is low for them.

Anything below 50% can severely affect the growth of ferns. 

Boston ferns are intolerant of low humidity.

It starts to dry out the leaves.

If the area of your ferns has a low humidity level in the air, it will make your ferns dehydrated.

Check for the signs of stress in your ferns.

Signs that your Boston fern is receiving less humidity are:

• Curling leaves
• Brown edges on leaves
• Yellow leaves
• Crispy foliage

Also read: Should I Mist My Boston Fern? (How Often+Pros & Cons)

Direct or low light

Boston ferns in nature grow under bigger trees in forests, so they stay protected from direct natural sunlight.

They don’t get exposed to the direct rays of the sun.

Therefore, you need to create a similar environment when growing Boston ferns indoors.

If your Boston fern receives direct sunlight, you will notice the fronds going yellow.

Eventually, they can also turn brown due to sunburn.

On the other hand, if the Boston fern doesn’t receive enough sunlight, it will turn yellow due to lack of light and reduced chlorophyll.

Also read: What Kind Of Lighting Does A Boston Fern Need?

Wrong use of fertilizer

Fertilizers fulfill the nutrient supply of indoor plants.

Although Boston ferns might not need a lot of fertilizers, they will need enough to get the nutrients they need.

Overfertilizing can cause yellowing of the leaves because it gets more nutrition than required.

Overfertilization also makes the plant weak and prone to pests and other diseases, leading to an unhealthy plant.

Some of the signs of overfertilization are:

• Yellow leaves
• Weak plant
• Wilting of leaves
• Stunted growth
• Dry plant

Underfertilization can also cause pale yellow leaves due to less nutrition.

You can fertilize with a balanced houseplant food. 20-10-20 NPK is ideal for a Boston fern.

You can add organic compost, pine bark, or perlite to the Boston ferns’ soil because they help keep the pH balance optimal for them.

Also read: Should I Fertilize My Boston Fern? (Ideal Fertilizer+When & How Much)

Transplant shock

Ferns need to be repotted when root bound or have undergone any root diseases.

They go through some stress after being transplanted.

This is natural, and you can’t prevent this, but to cause as minimal stress as possible, try to repot in the spring.

You must choose the right soil mix and a pot no more than 2 inches bigger than the existing pot.

After repotting, do not disturb the plant much.

Water only when the topsoil is dry. 

Keep it in a place where it gets bright but indirect sunlight and a lot of air circulation.

The plant needs to adjust to the new environment and thus look wilted and yellow for some time, but it will bounce back.

Pests

Boston ferns are susceptible to pests, including scale insects, mealy bugs, caterpillars, thrips, and spider mites.

A pest infestation can cause the fronds to turn light greenish-yellow in color.

These pests prefer moist, humid places to thrive, and ferns are a perfect place for them.

Even though they hate humidity and brightness, spider mites commonly attack Boston ferns and weave webs in the fronds.

This makes the fern look yellow and gives a speckled look.

Inspect your plant carefully for an infestation.

Examine carefully to watch for these pests because they are not easily visible.

If you see yellowing of the leaves, check the undersides of the leaves. 

Though several chemical pesticides are on the market, since pesticides easily damage ferns, it is better to use natural remedies to reduce the infestation.

It is recommended to use organic pesticides like Neem oil.

Fungal growth

Fungal attacks are common in high humidity areas because the moisture and weather conditions are perfect for fungus development.

If you overwater your Boston fern without checking the soil, it can also lead to root rot.

In such a situation, you should check the roots for any disease.

If the roots are mushy and brown or black, root rot might be the reason behind the yellowing of the leaves.

You must:

• Prune the decaying roots and repot.
• Reduce the watering.
• Check the pot for drainage holes.
• Change the soil if it holds excess water.

If the roots are tangled and growing in a circular motion, the reason for yellowing is a rootbound plant.

In this case, you will need to report the plant in a pot at least 2 inches bigger than the current one.

How to fix yellow leaves on Boston fern?

We discussed the various reasons that lead to the yellowing of the leaves of Boston ferns.

Here are some remedies that you must follow if you want to prevent the yellowing of your plant and give it healthy life.

Proper watering

Watering is one of the most basic routines for any plant.

However, too little or too much can harm your Boston fern. 

Boston ferns love moisture, but you must not overwater and make the soil soggy.

This can lead to yellowing and root rot in the plant, killing your plant. 

• Before you water, always check the moisture in the soil. Dip your finger, and if the soil sticks to your finger, do not water. You can also use the moisture meter for this.
• Use pots with drainage holes. 
• Change the watering schedule with the seasons. 
• Do not keep your fern thirsty and dehydrated, making it weak and wilted.

Controlling humidity

Boston ferns thrive in about 80% humidity in nature, but anything less than 50% will be seriously harmful to your Boston fern.

Low humidity will make the plant dehydrated and yellow. 

Regular misting is a good ad simple way to give the leaves some water and also helps to keep them clean.

• Use humidifiers to increase humidity around plants.
• You can also use pebble trays are another great way to increase humidity for Boston ferns. Place a few pebbles on a tray, fill the tray with water until the pebbles are half-drowned, and put the plant pot on the pebbles. As the water evaporates, it will raise the moisture around the Boston fern.
• You can also group the plants to increase the moisture in the place.
• Keep the Boston fern away from AC and heaters and vents as they can dry up the plant.
• Shifting your Boston fern to high humid areas like the kitchen, bathroom, and laundry rooms is also a great way to give humidity, provided these areas have good light and air circulation. 

Repotting

Boston ferns take time to get accustomed to the new condition generally takes some time. 

• Give the plant time to adjust by not disturbing and fidgeting with the plant too much.
• Make sure the pot is not too big and has drainage holes for the water to pass away.
• Keep the fern in an area with good light and air away from direct sunlight.
• Do not repot except in spring and early summer, and do not fertilize for a month after repotting. 

Fix the lighting

Light plays a crucial role, so make sure the plant is not in an area with low light or direct sunlight. 

Ferns cannot tolerate direct sunlight, which scorches and burns the leaves.

If you want to give it direct sun, the early morning sunlight is fine but keep it away from the afternoon sunlight.

If your home does not have sufficient light for your ferns, you can invest in artificial lights.

Pests

These nasty bugs are nightmares for every plant owner.

Let us quickly learn about some organic ideas to repel those bugs. 

Neem oil: It is a great anti-bacterial organic pesticide.

It removes all kinds of bugs and pests from plants without harming the plant like many chemical pesticides.

• Mix Neem oil with water.
• Add the mix into a spray bottle.
• Spray it all over the affected areas, and do not wash it.

This spray kills all the pests, which you can wash with plant cold water. 

Keep repeating it 2-3 times every week until your fern is clear of pests. 

Alcohol spray: Mix 2 cups of isopropyl alcohol with a quarter of the water and spray it on all the infected parts of your Boston fern.

It will remove all the pests. 

Soapy water: Add a few tablespoons of mild soap or shampoo to a gallon of water and spray it on the plant.

Keep it for a few hours, and then wash the plat thoroughly with clean water.

It will remove all the bugs and give your plant a fresh look.

Don’t use this too frequently as that can harm the plant.

Garlic: Many plant owners use this technique where they peel some garlic cloves and dig them inside the soil of the infested plant.

The strong smell repels bugs.

Using proper fertilizers

Overfertilizing can be equally harmful to your plants and result in root burn, leaf burn, and yellowing of leaves.

Boston ferns are light feeders, so you can feed them with 20:10:20 NPK in the growing season.

Do not fertilize on dry soil as that can burn the roots.

How do you prevent Boston ferns from turning yellow?

Let us quickly discuss some ways to stop the yellowing of the Boston fern leaves:

• Keep the fern away from direct sunlight. Keep it in a shaded place but receives good indirect light and air.
• Do not keep it in a dark or low-lit place.
• Trim the old, decayed parts so that the plant can put its energy into pushing new growth.
• Do not overwater your fern. Check the soil before watering.
• Your ferns need humidity. If you live in dry air, use artificial ways like a humidifier to increase humidity.
• Use distilled water instead of tap water for watering.

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Reference: University of Florida, The University of Arkansas Division, Texas A&M University System, The University of Georgia, University of New Hampshire, Wikipedia, The Royal Horticultural Society.