Selaginella willdenowii: The Iridescent Blue-Green Beauty

Meet Selaginella willdenowii

Selaginella willdenowii is a spectacular tropical spike moss best known for its unusual blue-green to blue-iridescent foliage. When the light catches the leaves at the right angle, the plant can develop an almost metallic blue sheen, making it one of those plants that looks slightly unreal.

It has a naturally creeping growth habit and loves warm, humid conditions, making it particularly well suited to tropical terrariums and vivariums.

Appearance

The foliage is delicate and fern-like, with tiny overlapping leaves arranged along branching stems. The most exciting feature is the blue-green to bluish iridescence that can appear across the foliage.

The colour can vary considerably depending on light, humidity, plant age and growing conditions. In some conditions it may look predominantly green, while in others the blue tones can be much more obvious.

It is a fantastic plant for adding texture and a little unexpected colour to a planted display.

Growth Habit

Selaginella willdenowii is primarily a creeping, spreading plant.

Its slender stems grow horizontally across moist surfaces and can root where they make contact with the substrate. Rather than growing tall, it gradually spreads into a low carpet.

It can also creep over suitable pieces of cork bark, wood and hardscape when conditions remain humid.

Growth Speed and Mature Size

Under warm, humid conditions, Selaginella willdenowii is generally a moderate grower.

It can spread steadily once established, eventually creating a dense mat of foliage. Its height generally remains low, with the plant putting much more energy into spreading sideways than growing vertically.

The available space largely determines its final footprint.

Lighting

Bright, indirect or filtered light is ideal.

Good lighting helps encourage healthy, compact growth and can enhance the plant's attractive blue-green colouring.

Avoid intense direct sunlight, especially through glass, as the delicate foliage can dry and scorch quickly.

In a terrarium, a quality full-spectrum grow light can work very well.

Watering

Selaginella willdenowii likes consistently moist conditions.

Do not allow the growing medium to dry completely for extended periods. Water when the substrate begins to lose moisture and keep it evenly damp.

However, moist does not mean waterlogged. The roots still need oxygen, so make sure the substrate drains well and does not remain stagnant.

Humidity

High humidity is essential for getting the best from this plant.

Aim for approximately 70–90% humidity, particularly in a terrarium or vivarium.

It can be grown outside a terrarium, but maintaining consistently high humidity can be challenging in an ordinary indoor environment.

Good airflow should still be provided to prevent stagnant, overly wet conditions.

Temperature

Warm, stable conditions are best.

Aim for approximately 18–27°C, with growth slowing as temperatures fall.

Avoid cold draughts and prolonged temperatures below approximately 15°C.

Soil and Substrate

Use a moisture-retentive but airy substrate.

A mixture of coco coir, sphagnum moss, fine orchid bark and perlite works well.

For terrariums, a loose tropical substrate is ideal. The growing medium should remain moist without becoming dense, muddy or anaerobic.

Fertilising

Selaginella willdenowii is a light feeder.

During active growth, use a very dilute balanced fertiliser approximately every 6–8 weeks.

Quarter-strength is generally plenty.

In an established terrarium, fertilising may be needed only occasionally, particularly if the substrate contains organic matter.

Climbing Support

A moss pole isn't necessary.

Selaginella willdenowii is primarily a creeping groundcover, so it is happiest spreading across the substrate.

It can, however, creep over cork bark, wood and other hardscape where moisture and humidity remain high.

Moss Pole, Plank or Hanging?

A flat growing surface is best.

Allow it to spread naturally across the substrate or over suitable pieces of cork and wood.

It isn't naturally a hanging plant, although sections can trail slightly over the edge of a container once established.

Encouraging Strong Blue Colour

The blue tones are one of the reasons people grow this plant, but colour can naturally vary.

Provide bright filtered light without harsh direct sun, good humidity and consistent moisture.

If the plant is kept too dark, it may appear greener and growth can become less compact.

Don't deliberately stress the plant to try to produce colour. Healthy growth should always come first.

Encouraging Dense Growth

Consistent moisture and humidity are the biggest factors.

Allow healthy stems to remain in contact with moist substrate so they can establish roots and spread.

If sections become excessively long or sparse, trim them and gently press healthy pieces onto the substrate.

Winter Care

Selaginella willdenowii does not appreciate cold, dry winter conditions.

Keep it warm and maintain humidity as consistently as possible.

Growth may slow when light levels decrease, so reduce fertilising and monitor watering carefully.

Don't allow the plant to dry out completely simply because it is winter.

Repotting

This plant does not require frequent repotting.

For container-grown plants, every 1–2 years is generally sufficient, or whenever the substrate has broken down or the plant has outgrown its growing area.

Because the stems are delicate, handle the plant gently when repotting.

A shallow, wide container can be particularly useful because the plant naturally spreads rather than growing deeply.

Hydroponic and Semi-Hydro

Selaginella willdenowii is better suited to moist soil-based or terrarium substrates than to conventional hydroponics.

It can tolerate very moist conditions, but permanently saturated roots can still suffer from poor oxygenation.

Semi-hydro may be possible for experienced growers, but it is not necessary. A good airy terrarium substrate is generally simpler.

Preventing Root Rot

The biggest mistake is assuming that because Selaginella loves humidity, its roots should always be soaking wet.

Use an airy substrate, provide drainage and avoid stagnant water.

In a terrarium, water sparingly and monitor the substrate rather than following a rigid watering schedule.

If the plant starts deteriorating while the substrate remains saturated, check the roots and improve drainage and airflow.

Acclimating After Purchase

Selaginella can be sensitive to sudden changes in humidity and moisture, particularly after shipping.

Place it somewhere warm, humid and away from direct sunlight.

Keep the substrate appropriately moist and avoid immediately repotting unless necessary.

Allow the plant time to adjust before making major changes.

Shipping Stress Recovery

Shipping may leave the delicate foliage curled, closed or slightly dry.

Restore appropriate moisture and humidity and provide stable warmth.

Don't repeatedly soak the plant in an attempt to force it to recover. Consistent conditions are much more helpful.

Some damaged foliage may not recover, but healthy stems can produce new growth once the plant settles.

Signs Your Selaginella willdenowii Is Happy

A happy plant will produce fresh creeping growth, dense foliage and strong green to blue-green colouring.

Healthy stems should remain flexible and gradually spread across the available substrate.

When it starts filling in around your hardscape and developing that gorgeous blue sheen, you're doing something right.

Pests

Selaginella willdenowii is not usually a major pest magnet, but stressed plants can still experience common pests.

Spider Mites

Spider mites are more likely when conditions become too dry. Look for fine webbing, tiny pale speckles and dull foliage.

Maintaining appropriate humidity is particularly important for this species.

Thrips

Thrips can damage tender growth, causing discolouration, scarring or distorted foliage.

Inspect new growth regularly.

Mealybugs

Mealybugs may occasionally hide amongst dense stems. Look for white, cotton-like clusters.

Early detection is much easier than dealing with an established infestation.

Propagation

Propagation is very straightforward.

Take healthy sections of creeping stem and place them directly onto moist growing medium.

Keep humidity high and make sure the stems remain in good contact with the substrate.

The plant can develop roots from sections of stem, allowing a small amount to gradually spread into a larger colony.

Common Problem: Brown or Crispy Foliage

Brown, crispy foliage is usually a sign of insufficient moisture, low humidity, excessive light or heat.

Check the substrate and humidity first.

Move the plant away from harsh sunlight and increase humidity if necessary.

Common Problem: Curling or Closing Foliage

Curling or closing foliage is often associated with dehydration.

Check the moisture level and humidity and restore consistent conditions.

If the stems remain green and healthy, the plant may recover surprisingly well.

Common Problem: Yellowing

Yellow foliage can indicate excessive moisture, poor airflow, root problems or unsuitable light.

If the substrate remains wet for long periods, improve drainage rather than increasing watering.

Common Problem: Loss of Blue Colour

If the foliage becomes noticeably greener, check the lighting.

Insufficient light can reduce the intensity of the blue-green appearance. However, natural variation is normal, so a greener plant isn't automatically unhealthy.

Common Problem: Sparse Growth

Sparse growth may be caused by low light, inconsistent moisture or insufficient humidity.

Improve the growing conditions and trim weak sections if necessary.

Healthy new growth should gradually fill the gaps.

Can Selaginella willdenowii Grow in a Terrarium?

Yes — it is an excellent terrarium plant.

Its love of humidity, creeping habit and unusual blue-green foliage make it especially attractive in warm tropical terrariums and vivariums.

It works beautifully as a foreground plant, groundcover or living carpet around larger plants and hardscape.

Best Terrarium Setup

A warm, humid tropical terrarium with high humidity, bright filtered lighting, consistently moist but well-aerated substrate and good airflow is ideal.

Closed or semi-closed terrariums can work very well, provided condensation and ventilation are managed.

It looks particularly impressive when allowed to spread around cork bark, wood, rocks and other natural hardscape.

Terrarium Maintenance

Keep the substrate moist but not saturated.

Trim sections when they become too long or start covering plants you want to keep visible.

Remove dead foliage and make sure the enclosure has enough airflow to prevent stagnant, constantly wet conditions.

Is Selaginella willdenowii Pet Safe?

Selaginella species are generally considered non-toxic, although detailed toxicity information can be limited for individual species and cultivars.

It is not considered a plant with the major toxicity concerns associated with plants such as Begonia or Dieffenbachia.

As with any ornamental plant, however, pets should not be encouraged to consume large quantities.

Is Selaginella willdenowii Reptile Safe?

Yes, Selaginella is generally considered a suitable choice for reptile enclosures, particularly humid tropical vivariums.

Its low-growing habit, delicate foliage and preference for high humidity make it useful as a groundcover or accent plant.

As always, "reptile safe" refers to suitability where incidental nibbling may occur rather than the plant being intended as a food source.

Final Care Tips

Selaginella willdenowii is one of those plants that makes you stop and look twice. Its delicate foliage is pretty enough on its own, but when the light catches those blue-green tones, it can look almost metallic.

Give it warmth, high humidity, consistent moisture, bright filtered light and an airy substrate, and allow it to creep naturally across the growing surface.

It is particularly impressive in tropical terrariums, where it can create a lush living carpet with a little flash of blue that makes the whole planting look more interesting.

Small leaves, low profile and absolutely no shortage of personality. This one definitely earns its place in the terrarium.