Selaginella Martensii

If you’re looking for a houseplant that’s both ancient in origin and surprisingly tough, let me introduce you to Selaginella martensii. This rare and resilient fern is a fantastic choice for adding lush, textural greenery to your home, especially in those tricky low-light spots where other plants might struggle.

Often called the Spikemoss or Frosty Fern, it’s not actually a true moss or fern but a lycophyte—a living relic from prehistoric times. Its creeping stems and delicate, fern-like foliage form beautiful, dense mats. While it can be a bit fussy about humidity, its toughness in other areas makes it a rewarding plant for attentive gardeners. Getting its care right means you’ll be rewarded with a vibrant, year-round carpet of green.

Understanding what makes this plant unique is the first step to keeping it thriving. Selaginella martensii is a slow-growing, spreading plant. Its most common variety has vibrant green leaves, but the ‘Jori’ or ‘Frosty’ cultivar is especially sought after for the white tips on its new growth, resembling a touch of frost. It’s a stellar choice for terrariums, closed glass containers, or as a ground cover in shady outdoor gardens in mild climates.

Ideal Growing Conditions

Mimicking this plant’s natural habitat is key. In the wild, it grows on forest floors, enjoying dappled light, consistent moisture, and high humidity. Your goal is to recreate those conditions inside your home.

Light Requirements

This plant thrives in medium to bright indirect light. Think of the light in a north-facing window or several feet back from an east or west window. Direct sunlight, especially the hot afternoon sun, will quickly scorch its delicate leaves, causing them to turn brown and crispy. If you only have a brighter spot, use a sheer curtain to filter the light.

Temperature & Humidity

Here’s where the “resilient” part meets its one major need. Selaginella martensii prefers consistent, room-temperature conditions between 60-75°F (15-24°C). It doesn’t like drafts or sudden temperature changes.

The critical factor is humidity. It needs high humidity, ideally above 50%. Dry air leads to brown, shriveled leaf tips. Here are a few ways to increase humidity:

Place the pot on a pebble tray filled with water (ensure the pot sits above the water line).
Group it together with other humidity-loving plants.
Use a room humidifier nearby, which is the most effective method.
Grow it in a sealed terrarium, which creates a perfect miniature ecosystem.

Choosing Soil and Potting

The right foundation prevents countless problems. This plant needs a soil mix that retains moisture but also drains well to prevent root rot. A standard potting soil is too heavy on its own.

A perfect mix could be:

2 parts peat-free houseplant compost or coco coir
1 part perlite or pumice
1 part fine orchid bark or horticultural grit

This combination holds moisture while letting excess water flow away freely. Choose a pot with drainage holes. Plastic or glazed ceramic pots help retain soil moisture longer than porous terracotta.

Watering Your Spikemoss Correctly

Watering is perhaps the most common point of failure, but it’s simple once you know the rule. The goal is to keep the soil consistently moist, but never soggy. Think of the dampness of a wrung-out sponge.

Check the top inch of soil frequently with your finger.
When the top feels just slightly dry to the touch, it’s time to water.
Water thoroughly until water runs out of the drainage holes.
Always empty the saucer or cache pot after 15 minutes so the plant isn’t sitting in water.

Using lukewarm, distilled, rainwater, or filtered water is best, as this plant can be sensitive to the chemicals and minerals in tap water. Underwatering causes the stems to dry out and die back, while overwatering leads to yellowing leaves and root rot.

Feeding and Routine Care

Selaginella martensii is not a heavy feeder. During its active growing season (spring and summer), you can feed it once a month with a balanced, diluted liquid fertilizer. Use half the strength recommended on the bottle. There’s no need to feed it at all during the fall and winter when growth naturally slows.

Pruning is straightforward. Simply trim back any long, straggly stems or remove any sections that have browned using clean, sharp scissors. This encourages bushier, more compact growth. You can also gently mist the foliage between waterings to boost humidity, but avoid misting if you’re keeping it in a terrarium.

Propagation Methods

Sharing this rare plant with friends is easy. The most reliable method is by stem cuttings or division.

Division (Easiest Method):

When repotting, gently tease apart a section of the plant with your fingers, ensuring it has both stems and roots attached.
Pot this new section into its own container with fresh, moist potting mix.
Keep it warm and humid while it establishes.

Stem Cuttings:

Cut a healthy stem tip about 3-4 inches long.
Remove the leaves from the lower inch of the stem.
Place the cut end into a small pot of moist potting mix or even just lay the cutting on top of the soil.
Cover the pot with a clear plastic bag to create a mini greenhouse, and keep the soil moist. Roots should develop in a few weeks.

Common Problems and Solutions

Even with great care, issues can pop up. Here’s how to troubleshoot.

Brown, Crispy Leaf Tips: This is almost always caused by low humidity. Increase moisture in the air using the methods described earlier.
Yellowing Leaves or Stems: Usually a sign of overwatering. Check the roots for rot (they’ll be mushy and dark) and let the soil dry out a bit more between waterings. You may need to repot into fresh, dry mix.
Leggy, Stretched Growth: The plant isn’t getting enough light. Move it to a brighter location with indirect light.
Pests: While not common, mealybugs or spider mites can sometimes appear. Wipe leaves with a damp cloth or use an insecticidal soap spray, avoiding harsh chemicals.

Design Ideas for Your Home

Beyond the terrarium, Selaginella martensii’s trailing habit makes it versatile. Try it in a hanging basket where its foliage can cascade down. It works beautifully as a living centerpiece in a shallow, wide bowl. You can also plant it at the base of larger, upright houseplants like a Fiddle Leaf Fig to create a lush, layered look. Its preference for shade makes it ideal for brightening up a dim bathroom shelf, provided there’s some natural light.

Frequently Asked Questions

Is Selaginella martensii safe for pets?
Yes, it is generally considered non-toxic to both cats and dogs, making it a pet-friendly choice.

Why are the white tips on my ‘Frosty’ fern turning green?
The white variegation is most prominent on new growth and in cooler conditions. With age, or if the plant is too warm, the white tips may fade to green. This is normal and not a sign of poor health.

How often should I repot my Spikemoss?
Repot every 2-3 years in spring, or when you see roots growing out of the drainage holes. It prefers to be slightly root-bound, so only move it to a pot one size larger.

Can I grow Selaginella martensii outdoors?
In USDA hardiness zones 10-11, you can grow it outdoors in a consistently shady, moist spot. In cooler climates, it must be brought indoors before the first frost.

My plant looks dry even though I water it. What’s wrong?
Check the root ball. Sometimes, peat-based mixes can become hydrophobic—they repel water—especially if they’ve dried out completely. Soak the entire pot in a basin of water for 30 minutes to rehydrate the soil thoroughly.

Caring for Selaginella martensii is a lesson in providing consistent, gentle care. It asks for little but humidity in return for its beautiful, prehistoric charm. By following these simple guidelines, you can enjoy this rare and resilient fern as a thriving part of your indoor garden for many years to come. Its unique texture and rich color are sure to make it a conversation piece among your plant collection.