Best Soil Mix for Boston Ferns to Thrive

Boston ferns (Nephrolepis exaltata) grow best in a light, moist, well-draining soil mix. I find an acidic pH — between 5 and 5.5 — is ideal. My favorite homemade soil recipe for Boston ferns incorporates one part standard potting mix and one part peat moss, as are two parts peat moss, one part perlite, and one part vermiculite. Above all else, the soil must never be allowed to dry out completely, as Boston ferns love moist and humid soil conditions to thrive indoors.

The Best Soil Mix for Boston Ferns (Essential Tips)

The Importance of Well-Draining Potting Soil for Boston Ferns

Though Boston ferns need moist soil and humid conditions to thrive (similar to most types of indoor ferns), that doesn’t mean they like to sit in wet soil. In fact, wet, soggy feet may cause a host of problems for Boston ferns. 

Instead, they need well-draining potting soil that allows air circulation around roots. If soil retains too much water, the ferns may suffer root rot. Use potting soil that drains well while retaining enough moisture.

What pH levels in the Soil are Best?

In my experience, Boston ferns prefer acidic soil. Aim for a pH level between 5 and 5.5. Using potting soil that contains peat moss is an excellent way to ensure proper pH levels for your Boston fern.

Common Signs You’re Using the Wrong Soil Mix

When Boston ferns are planted in the wrong soil mix, the plants will let you know. Among the most common issues? Planting Boston ferns in soil that doesn’t retain enough water. When Boston ferns are too dry, the tips and edges of the fern’s pinnae will turn brown and may look “crispy.” The plant may take on a gray cast and stop growing.

I find that ferns may also start shedding fronds if the humidity remains too low. Speaking of humidity, if available moisture is too low, fronds will turn yellow. Continued low humidity and dry soil make Boston ferns more susceptible to pests such as scales or spider mites.

The Ultimate Boston Fern Potting Mix Home Recipe

A small Boston fern plant with green crinkly leaves in a white plant pot on a  circular table in a living rooms indoors

Making the ultimate potting mix for your Boson fern is simple. Your goal is to create a supportive soil with acidic pH that provides support and nutrients for your plant, retains the right amount of moisture, and allows water to drain.

Here’s my easy, one-to-one recipe, which is an excellent place to start:

  • One part standard potting mix
  • One part peat moss

If you want to increase drainage, this four-part recipe offers excellent aeration while still remaining moist:

  • Two parts peat moss
  • One part perlite
  • One part vermiculite

Make sure to thoroughly combine the components before adding the mix to a pot.

Why Soil Choice Matters

A person gathers a handful of soil from a plant pot indoors

Does the soil you use to plant Boston Ferns really matter? Along with light, temperature, and humidity, the soil is key to your plant’s health and survival.

Of course, soil anchors your plant in place, providing a solid foundation in which roots can take hold. But soil also provides nutrients, oxygen, and water that plants need. 

The type of soil you choose impacts how a plant grows and can even determine if a plant thrives or not. 

Soil supports plant growth in several fundamental ways, including:

  • Stability: Plants’ root systems extend throughout and down into the soil, anchoring plants in place and keeping them stable.
  • Water: The spaces or pores in between soil particles contain water, which plants absorb through their roots. As water travels throughout the plant, it provides nutrients and oxygen, supports photosynthesis, and cools plants as it evaporates from foliage.
  • Oxygen: Soil pores also contain air, which has the oxygen plants use to transform sugars into energy and growth.
  • Nutrients: Soil contains the minerals that plants need to survive in the form of micro-and macronutrients like nitrogen, magnesium, calcium, zinc, copper, and more
  • Protection from temperature fluctuations: Soil acts as an insulation for plant roots, keeping them safe from drastic modifications in temperature.

Soil is composed of minerals (from rocks) and organic biomass (from decomposing plants and animals). The mineral portion of soil is defined by its texture, which consists of differently sized particles:

  • Sand: The largest particle size, sand particles can be seen with the naked eye. Sandy soil drains quickly and offers excellent aeration. It also erodes quickly and doesn’t hold moisture or nutrients well.
  • Clay: The smallest particle size, clay particles can only be seen through a microscope. Clay doesn’t contain much air, and water drains very slowly through it. This means it erodes slowly and holds onto water and nutrients.
  • Silt: Silt particles fall between sand and clay particles in size.

Most soils contain a mixture of sand, clay, and silt. Often, soil that consists of a relative balance of the three particle sizes is known as “loamy.”

Soil that contains a high amount of decomposed organic matter is known as “peaty.” Peaty soil offers both water retention and increased airflow. 

In contrast, “chalky” soil contains high levels of calcium carbonate. Chalky soil tends to be alkaline, free-draining, and doesn’t hold many nutrients.

When choosing a soil type, consider a plant’s soil preferences. The right soil type can be the difference between a plant that struggles and a plant that thrives.

What are the Primary Components Used in a Potting Soil Mix?

Three pots of different soil components on a wooden table

What’s in a good potting soil mix? Potting soil contains a blend of elements that can hold moisture and nutrients, allow water to drain, and let air circulate around roots. This is especially important for plants grown in containers, such as Boston ferns.

Potting soil may contain the following primary components:

  • Coco Coir: Fibrous material from coconut husks that increases water retention when added to potting soil.
  • Compost/organic matter: Aged forest or garden products that have been safely composted or broken down biologically by soil microbes like beneficial bacteria and fungi. Compost provides necessary nutrients to potted plants.
  • Perlite: Volcanic glass that’s composed of silicon dioxide. Improves moisture retention, drainage, and aeration, while loosening clay or compacted soil.
  • Pine Bark Fines: A byproduct of pine bark mulch production, these tiny slivers of pinewood help improve drainage and increase soil acidity.
  • Pumice: A light, porous volcanic rock that improves drainage and air circulation while supporting advantageous microbial life.
  • Sand: Largest soil particle size; adds air to potting soil mixes.
  • Soil Activator: Compounds containing humic acids that help break down organic matter in the soil. May improve plant chelation or ability to absorb metals from the soil.
  • Sphagnum Peat Moss: This popular soil amendment consists of decayed plant matter from sphagnum moss that grows in wetlands and bogs. It helps loosen clay soil and increase drainage and help sandy soil retain moisture.
  • Vermiculite: A lightweight, mineral-based soil amendment that increases water and nutrient retention while improving aeration.

Soil Mix for Boston Ferns FAQs:

How often should I switch soil for my Boston Fern? 

As a general rule, repot your Boston fern with fresh potting soil every two to three years. If you notice roots protruding from the button of the container, soil that dries too fast, or a decreased foliage growth rate, you may want to repot your fern in a larger container with fresh potting soil mix.

Can I use cactus soil for Boston Ferns? 

Don’t use cactus soil for Boston ferns. This light soil drains quickly and doesn’t tend to hold moisture, and likely won’t provide enough humidity for Boston ferns to thrive.

Do Boston Ferns like wet or dry soil? 

Boston ferns do not like dry soil, but they don’t want to be soggy, either. They prefer moist, well-drained soil.

What are the primary considerations for soil when repotting a Boston Fern? 

Repot your Boston fern in spring, when the plant is actively growing. Water the plant a couple of days before reporting, and choose a container that’s only 1 to 2 inches larger than the original pot. Plant the fern at the same depth; planting too deeply can lead to root rot.

Does the size of the plant affect the soil mix for Boston Ferns? 

Boston ferns always prefer moist, well-draining soil with an acidic pH, regardless of plant size.

Does the potting container influence the type of soil mix for Boston Ferns? 

Boston ferns love humidity, so using a double container may help your plant thrive. Pot it in a small terracotta pot with suitable drainage holes, then place that pot in a larger container lined with peat moss to increase humidity.

Do Boston ferns need deep potting containers? 

Boston ferns don’t need particularly deep containers to thrive.

Wrap Up

Boston ferns add a lush tropical look when grown indoors. Native to humid and warm environments, Boston ferns need adequate moisture and humidity to thrive. Well-draining potting soil that retains moisture and offers an acidic pH is key to growing thriving ferns.

For more, see our essential Boston Fern plant care guides:

Contributing Editor | | Full Bio

Linsay is an American copywriter based in the Pacific Northwest with a background in academic writing and research. Linsay holds Master's degree in both Anthropology and Library and Information Sciences and has written for numerous national and international publications including USA Today, SFGATE, Hunker, and The Bump across an array of topics in the gardening, green living, and travel sectors. When she's not writing, you'll usually find Linsay reading, kayaking, sailing, snowboarding, or working in her garden.

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