Why Your Boston Fern is Turning Brown

Wondering why your Boston fern is turning brown? Look no further! Discover the leading causes for your browning fern and how to bring it back to life.
boston fern
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Brown spots on Boston ferns may just be spores, a normal part of the fern’s reproductive process. Don’t panic!

Over-fertilization can lead to brown, brittle fronds. Be mindful of how often you fertilize and test your soil before doing so.

Proper watering and humidity levels are crucial for maintaining healthy Boston ferns. Find the right balance and don’t forget to check humidity levels!

The Boston fern is a beloved houseplant, known for its stunning green fronds that bring texture and vibrancy to your living space. They’re a type of evergreen fern that are native to several regions, including Florida, West Indies, Mexico, Central America, South America, Polynesia, and Africa. Boston ferns can grow up to 3 feet in both height and width because of their upright and spreading growth habit. When in their native environment, they can even reach a towering height of up to 7 feet.

Although, there are times your Boston fern may look lackluster. Seeing brown fronds can be alarming, but there’s no need to panic. A good starting point to ease your worries is to determine the potential cause of the discoloration.

Boston Fern Spores
Close-up of fern spores

It’s important to know that not all brown spots on Boston ferns are a cause for concern. The brown spots on your Boston fern may be spores, which is a normal and natural way for the fern to reproduce. You can find the sori, or spore sacs, in lines on the underside of each leaf. The sori are small and round structures that can appear brown or black. Once mature, the spores will fall to the soil and develop into reproductive structures. The presence of spores is a positive sign that your Boston fern is healthy and growing.

The older leaves near the base of your Boston fern may become discolored and turn brown or black as new growth emerges. If you want to your fern’s fresh appearance, you can simply cut away any discolored leaves.

Over-Fertilizing
Tips of fern fronds turning brown.

Brown, brittle fronds can be a sign of over-fertilization. Excess soluble salts and fertilizers can cause plant damage, such as wilting, yellowing, browning, and stunted growth. Over-fertilized ferns become weak making them more prone to diseases and insect infestation, especially from sap-feeding insects. Boston ferns need nutrient-rich soil or regular fertilization with liquid or slow-release houseplant fertilizer every four to six weeks during their active growth period.

Boston ferns experience dormancy during winter, and excessive fertilizer can harm their roots and leaves. Reduce fertilizer during this period to prevent root burn and accommodate their slower growth. Cold temperatures also slow down their metabolic process, hindering their ability to absorb nutrients from the fertilizer. It’s always a good idea to test your soil before fertilizing. The ideal soil for Boston ferns is fast-draining and has a pH level of 5 to 5.5.

It’s best to give the roots of newly potted plants time to establish before applying fertilizer. Newly potted Boston ferns require a warm and humid environment, and it takes approximately two to three weeks of regular watering for their roots to establish.

Watering
Fern in a basket being watered with spray bottle.

Boston ferns need watering once a week, but this may vary depending on pot size, humidity, and temperature. Typically, you should water potted plants until water drains from the bottom.

You can check if your fern needs watering by inserting your finger an inch into the soil and feeling for dryness. Watering your Boston ferns in the morning is an excellent practice that allows the leaves to dry before the sun evaporates everything. If your ferns are under-watered, the once lush green fronds will gradually turn brown and become crispy to the touch. On the other hand, over-watering may lead to root decay, causing the fronds to turn brown and yellow.

The key is to strike a delicate balance between moist soil and proper drainage. Leaving your Boston fern in stagnant, un-drained water can cause root rot and fungal problems. Keep in mind the environment can impact your fern’s watering needs. Bostons fern may struggle to absorb nutrients if it’s in a low-lit area, as the soil stays damp longer. Combating prolonged dampness is easy as watering less frequently to promote better drainage.
Humidity

Variety of dry fern fronds

A lack of moisture in the air can have a detrimental impact on many tropical indoor plants, including Boston ferns. When Boston ferns are suffering from a lack of humidity, they will appear dry and brown around the edges of their fronds. The fronds may also begin to curl and wilt before falling off entirely. Low humidity levels in a home are about 10 to 15 percent. The best humidity levels for Boston ferns are between 40 and 50 percent, but they can tolerate levels as low as 30 percent. Watch for signs of low humidity and address the issue right away to prevent further damage and help your fern bounce back.

There are many ways to save your stunning Boston fern fronds from dry air, like creating a micro-environment by grouping plants together, or placing a humidifier nearby. Another easy fix is to put a tray with a mixture of pebbles and at least ¼ inch water near your Boston fern. As the water evaporates from the pebbles, the air around your fern will become more humid.
Lighting

A fern hanging in the sunlight.

Boston ferns require a minimum of two hours of indirect sunlight to stay healthy. Boston ferns prefer bright, indirect light and can be sensitive to direct sunlight or too little light. Exposure to intense lighting or direct sunlight can scorch the Boston fern’s fronds, turning them brown. Ferns that aren’t receiving enough light can also turn brown from stress. During the summer, Boston ferns prefer bright but indirect light. However, in the winter, they can tolerate lower light levels.

Place your Boston fern in an area that receives at least two hours of filtered sunlight during early morning or late afternoon. A sunroom, a screened-porch, or an area close to a window with sheer curtains are a few examples of spaces that receive filtered sunlight.
It’s Not Easy Being Green

No more brown Boston ferns for you, my friend! You’re all set to add those green beauties to your home décor. Remember to share this article with your fellow plant lovers and let them in on the secrets. If you have any questions, just ask, and don’t be shy, spill the tea in the comments below on your own tricks for keeping your ferns looking fresh.

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