Boston Fern Temperature and Humidity Tolerances Indoors

In my experience, Boston ferns grow best indoors, where ambient temperatures remain between 60 and 75 degrees F. They thrive in humidity levels of 60 to 70% (or more). It’s easy to provide these conditions by avoiding dry or cold areas. Small plant humidifiers can help to provide sufficient supplemental moisture for those in particularly dry climates. This guide will take you through everything you need to know about Boston Fern plants’ ideal temperature and humidity ranges. 

Boston Fern Temperature and Humidity Tolerances Indoors

Native Temperature and Humidity Ranges Boston Ferns Receive

Boston ferns (Nephrolepis exaltata) are native to some parts of the U.S., including the southernmost parts of Florida. The plant is exposed to very humid conditions year-round in that area and other subtropical parts of the Pacific Islands and South America. It’s also kept above freezing throughout the year and doesn’t have to deal with cold damage to its roots or foliage. 

Like many types of ferns, the Boston fern is also an understory plant, living below the mature trees of the forest. The plant prefers indirect light inside the home instead of direct sunlight from a window. It’s pretty easy to replicate these conditions in most indoor environments with extra care. 

For a specific temperature range, Boston ferns usually experience temperatures as low as the 40s and as high as the low 90s. They prefer the center of this temperature range rather than the extremes. It’s native to parts of the U.S. with a USDA climate zone of 9 and above, so it can handle brief exposure to temperatures near freezing. 

Humidity levels range from 60% and up to 90%. The lower end of this range is definitely achievable within the home environment.

Signs Your Boston Fern is Exposed to the Wrong Temperature and Humidity

When a Boston fern gets too warm, it tends to lose its vigor and go limp or wilting. The plant should recover within a day or two once it’s returned to a cooler and more controlled environment. 

Boston ferns that are exposed to temperatures below freezing will suffer more pronounced damage. Many outer fronds can die off or display signs of yellowing from the exposure. If you manage to get the plant indoors before it is too severely exposed, it may grow back from the remaining foliage. 

More subtle signs of incorrect temperature and humidity exposure include brown, curled tips. These may continue even when you water the plant’s soil more evenly. You’ll also want to watch out for common Boston fern pests and diseases, which often thrive when plants are grown in less-than-ideal conditions.

Ideal Temperature and Humidity Considerations

A Boston fern in a wicker plant pot on a wooden table indoors

Boston ferns are sometimes kept outdoors. However, it’s harder to maintain a specific temperature range for them in an exposed environment. 

When kept indoors, it’s easier to maintain a specific temperature that helps this houseplant thrive. Unlike more sensitive houseplants, Boston ferns can handle a wide range of temperatures without suffering from damage. They must be kept above 40 degrees F and below 85 degrees F as much as possible. They can handle temporary dips above and below this temperature range, but never below 32 degrees F or much above 95 F. 60 to 70 degrees F is the ideal temperature range for this plant.

Regarding humidity, these ferns prefer a range between 60% and 90%. It’s harder to achieve a high level of humidity inside the home, but these plants will do well at just 60% to 70%. 

They don’t need to be dripping with moisture just to stay lush and green. However, adding a humidifier or misting the plant regularly will prevent brown edges and other signs of low humidity.

You can’t guess at the temperatures and humidity level around your houseplants and expect them to thrive, especially the Boston fern. A high-quality digital thermometer with a hygrometer function will allow you to track both. Look for a model with a history feature to determine if your plant experienced a sudden dip in either temperature or humidity any time recently. 

Avoid windows with direct sun exposure that can dry out the Boston fern and cause sunburn. West and south-facing windows are likely too direct for the fern. 

Stay aware of sources of drying drafts in the home that might also lead the Boston fern to overheat or freeze, such as air conditioning and heating vents, space heaters, and open windows or doors.

I’ve had success growing Boston Ferns in several locations throughout the home, including bathrooms, kitchens, and living rooms. 

How to Boost Humidity in Your Home

An indoor plant humidifier surrounded by several tropical houseplants

Since the Boston fern likes a higher average humidity than the 40% to 50% found in most homes, you’ll need to do something to help boost humidity. 

There’s no need to raise the humidity level in the whole home just for a few plants in one room. Instead, consider targeted methods such as a smaller humidifier unit placed near the ferns. 

Misting the plants can also help because they tend to have tightly clustered fronds that trap moisture and raise the surrounding humidity. 

Humidity trays don’t really contribute a lot of humidity to the air around a plant like a fern. Instead, consider either manual misting or putting a humidifier on a timer to run for a few hours a day. 

Grouping plants tightly together and keeping more than one of them at a time can also help trap humidity in the area. 

Consider a small table fountain or similar water feature to introduce some moisture into the air without having to mist all the time by hand.

(Editors Note: Petal Republic participates in partnership programs with Amazon and other merchants to help connect readers with relevant products and services we may recommend).

Caring for Boston Ferns in Spring and Summer

Green fronds of a Boston fern plant

Boston ferns are unique houseplants because they adapt well to being placed outdoors in the summer, especially if you live in a humid area. 

If you have warm and wet spring conditions and don’t mind watching for frosts, you can also try placing the plant outdoors during that season. 

Most people hang their Boston ferns in baskets on a covered porch or similar areas to protect them from direct sun and harsh wind. If you want to keep the plant indoors, keep it well away from air conditioner vents and watch how the summer becomes more direct as summer arrives. 

You may need to change where the plant is located so it doesn’t overheat and dry out too quickly if it’s placed in a warm spot from the winter. 

The Boston fern will need the least humidifier use in the summer unless you constantly experience a lot of drying heat or run the air conditioner.

Now’s also the best time to repot your Boston fern if needed, as well as fertilize and propagate if you’re looking to expand your collection. 

Caring for Boston Ferns Over Winter

Winter heating will dry out the air in the home and make humidity levels far too low for the Boston fern. 

Many people that buy them in the summer and keep them outdoors in a humid environment often think that these ferns can’t be kept over the winter without turning brown and shriveling up. It’s simply an issue of a lack of humidity in most homes. 

Use a misting bottle if you must, but a humidifier will work much better in the winter when the heating system removes so much moisture from the air. 

Make sure the Boston fern isn’t located too close to a cold surface like a window or in the path of a door that opens to the exterior where cold drafts could occur. You want to position the Boston fern in a warmer room of the home. However, watch for air vents blowing heated and dry air directly on the plant’s fronds.

Boston Fern Temperature and Humidity Tolerances FAQs:

What temperature is too cold for Boston Ferns? 

Boston ferns can handle colder temperatures than most houseplants, but they will wilt from anything below 40 degrees F for more than a brief time.

What temperature is too hot for Boston Ferns? 

These ferns prefer more moderate temperatures and may wilt from extended exposure to anything above 85 degrees F. Direct sun increases the damage from any heat exposure.

Are Boston Ferns heat sensitive? 

They don’t do well in temperatures above 80 degrees for long. Generally, they prefer to stay between 60 and 70 degrees, which is easily achieved all year round inside the average home.

Can I leave my Boston Fern outside? 

Boston ferns can be brought outside and left for months in the summer for most of the country. In USDA zones 9b and up, it can be planted in the ground or in containers and left outside year round.

How do I know if my Boston Fern is healthy? 

A healthy Boston fern will have perky leaves, even if they are curved, and will maintain a deep green color unless it’s a golden variety. It shouldn’t have any brown tips or soft-looking fronds.

Wrapping Up

Maintain a Boston fern from the summer through fall and winter with an eye to providing the proper temperatures and humidity levels. Try clustering these plants together since the dense foliage can trap moisture and help buffer them from dry air.

Editorial Director | | Full Bio

Andrew is the Editorial Director at Petal Republic. He holds a BSc degree in Plant Sciences and has trained professionally at leading floristry schools in London and Paris. In amongst overseeing a global editorial team, Andrew's a passionate content creator around all things flowers, floral design, gardening, and houseplants.

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