The Complete Guide to Fern Moss (Thuidium delicatulum)

Honestly, Fern Moss is as delightful as it sounds. 

With fine textured leaves resembling miniature fern fronds, it’s the perfect complement to a tropical or woodland scene. That’s why it’s such a popular pick for terrariums and gardens alike.

Of the many species of Fern Moss, Thuidium delicatulum is perhaps the most common in the trade and the most fern-like of them all. Hence the name Common Fern Moss.

As a pleurocarpous moss, it’ll form a dense layer of soft ferny goodness, and it’s prized for its easy care and distinctive triangular frond-like leaves (that are often quite large for a moss).

Find out how to grow this beautiful moss and keep it looking its best!

Where to Buy Fern Moss

See the links below to purchase from reputable terrarium plant shops and marketplaces (may include affiliate links). 

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Thuidium delicatulum Care & Growth

Plant TypeMoss
LightingMedium – high indirect light
Temperature60-80°F (15-26°C)
WateringRegular, even moisture
HumidityHigh humidity (60-90%)
Growth1-8 inches

Lighting

Thuidium delicatulum will do well in shaded environments. 

It’s naturally found growing terrestrially on woodland floors and epiphytically on rocks and fallen trees. So this moss is used to receiving only dappled, indirect light.

This makes Fern Moss an obvious fit for woodland-style gardens and terrariums. 

It’s such a beautiful moss. We’ve used it in a variety of projects.

That said, in low light conditions, you can see it grow quite leggy, with lots of individual leaves reaching up toward the source. Honestly, it’s not a good look… So you can either trim these down or provide a stronger light source (e.g., a grow light or a more sunny spot).

It can tolerate some partial sun, but it’s best to keep it out of direct sunlight to avoid leaf burn.

Watering

Fern Moss is often found in wetland areas, so you can expect it to like plenty of moisture.

It’ll do nicely in a closed terrarium environment and in partially closed vivariums with a misting system in place.

Consistent moisture is the key.

This is especially true during this moss’ acclimatization phase. It’s essential that you do not allow Fern Moss to dry out in the first few weeks of adding it to a container. After that, you’ll have more wiggle room on the watering front.

You can soak it for 20 minutes in water beforehand to give it the best chance.

Soil / Substrate

As this Fern Moss loves damp conditions, a water-retentive substrate will work best

Something that can hold moisture throughout so that the shallow root-like structures of the moss can freely access it. A coco coir base is a great starting point for terrarium mixes.

However, this moss does not like to be completely bogged down with water. So it’s helpful to have some elements of drainage in your mix, e.g., orchid bark or lava rock.

👉 Our terrarium substrate mix is a well-balanced option for tropical terrariums of all kinds.

When growing outside, replicating the acidic soil conditions of its native wetland environments can help to optimize its growth. 

Temperature & Humidity

High humidity goes a long way in preventing water loss, so this moss will love those bigger numbers. 

Realistically, the higher, the better on the relative humidity front. It’s easy to start pushing the 90% plus numbers in closed terrariums.

holding fern moss above terrarium
Fern Moss loves being in a humid closed terrarium.

For temperatures, this moss is naturally found in a variety of environments, so it should tolerate a variety of terrarium conditions, too. It should do absolutely fine in household temperatures, so you don’t need to worry about it too much.

Growth

The wild growth appeal of Thuidium delicatulum comes from its branching stems.

With each new stem radiating outwards from its primary stem, together, they create a dense layer of compounding green leaves. Combined with the textured frond-like leaves, the result really is stunning!

The 3D effect is lovely.

Fully grown, it really can begin to look more like a small fern than a large moss. 

It’s not unusual to get a carpet layer that’s at least several inches thick. So, in the long-term, it’s probably a better fit for large terrariums/vivariums where you need to add a wild element highlight.

We’ve used it (along with a variety of other mosses) in our latest tank terrarium.

Smaller terrariums can eventually get overwhelmed by this type of Fern Moss, though I guess if you start with just a small chunk, it’ll likely take a long time to get there.

It’s a great epiphytic grower too, so adding it to larger hardscape branches is a fantastic way to visually elevate a more substantial terrarium project. It’s easy to establish terrestrially and epiphytically as long as it’s kept moist and humid.

Naturally, it’s a great fit for a shaded woodland garden. Once it’s formed a thick carpet, it’ll just continue to thicken and grow upwards with ever-larger leaves. 

fern moss tiny terrarium
As a quick grower it’s not the best choice for mini, mini terrariums!

Propagation

Much like other carpeting terrarium mosses, Fern Moss will happily propagate through division.

Tearing off patches and placing them around a terrarium or garden can help it grow a carpet faster, as each new moss colony will grow outwards.

Despite its other common name, “Delicate Fern Moss,” it’s actually quite tough!

I’ve found it by far the most difficult moss to work with. So, you’ll have to really manhandle it to get it apart (or secateurs might be put to good use here).

trimming fern moss
We use aquascaping scissors to trim off the excess fibrous tissue too.

Varieties & Similar Plants

Fern Moss is a term used for a variety of moss species from the Thuidium genus.

These include Kilt Fern Moss (Thuidium recognitum) and Tamarisk Moss (Thuidium tamariscinum). You can also check out the likes of Hypnum Moss for another great ground-cover option.

There are some similarities between Hypnum Moss and Fern Moss, but the texture is really quite different.
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