Selaginella martensii, often called frosty fern, presents intricate, fern-like fronds with a distinctive frosted appearance. This unique plant adds a touch of delicate texture to indoor spaces, but it requires specific care to truly thrive. If you’ve recently brought one home or are considering it, understanding its needs is the key to success.
Despite its common name, it is not a true fern but a spikemoss. This distinction is crucial for its care. Its beautiful, almost lace-like foliage can be a long-lasting feature in your home with the right approach.
Selaginella Martensii
Belonging to the ancient Selaginellaceae family, Selaginella martensii is a vascular plant that reproduces via spores, similar to ferns. Its most striking feature is the variegated coloring on the tips of its tiny, overlapping leaves. New growth emerges with a creamy white or silvery hue, creating that “frosted” effect against the deep green mature foliage.
In its natural habitat, it grows as a creeping ground cover in humid, shaded forests. This tells you everything about the environment it prefers in cultivation: consistent moisture, high humidity, and protection from direct sun.
Key Characteristics And Identification
You can identify Selaginella martensii by a few key traits. The stems are slender and tend to sprawl or trail as they grow. The leaves are minute and scale-like, densely covering the stems in a pattern that resembles a flattened fern frond.
The frosted tips are most prominent on new growth and may become more green as the leaf ages if light conditions are not ideal. In very low light, the variegation can fade. It rarely flowers indoors; its reproductive structures are small spore cones at the tips of stems.
Common Varieties And Cultivars
While the species form is most common, you might encounter a few named cultivars. ‘Variegata’ is essentially the standard frosted form. ‘Jori’ is another popular cultivar known for its particularly bright white tips and compact growth habit. Sometimes you may find it simply labeled as “frosty fern” or “variegated spikemoss” at garden centers.
Ideal Growing Conditions and Environment
Recreating the plant’s native tropical understory environment is the secret to keeping your Selaginella martensii healthy. It is not a plant that tolerates neglect or fluctuating conditions well. Getting these core elements right from the start prevents most common problems.
Light Requirements: Avoiding Direct Sun
This plant requires bright, indirect light. Think of the dappled light on a forest floor. An east-facing window is often perfect. A north-facing window can work if it is bright enough.
- Direct sunlight, especially from a south or west window, will quickly scorch the delicate leaves, causing them to turn brown and crispy.
- Too little light will result in leggy growth, with stems stretching out weakly, and a loss of the vibrant frosted variegation.
- If natural light is limited, consider using a grow light placed about a foot above the plant for 10-12 hours a day.
Temperature And Humidity: The Critical Duo
This is where many growers face challenges. Selaginella martensii prefers consistent, moderate temperatures and very high humidity.
Optimal Temperature Range
Keep your plant in an environment between 60°F and 75°F (15°C – 24°C). It is crucial to avoid drafts, both cold from windows or doors and hot from heating vents or radiators. Sudden temperature drops can cause shock and leaf drop.
Mastering Humidity Needs
Aim for humidity levels above 60%. Typical household humidity, especially in winter with heating, is often below 40%, which is too dry. Here are effective ways to increase humidity:
- Use a humidifier: This is the most reliable and effective method for maintaining constant high humidity.
- Pebble tray: Place the pot on a tray filled with water and pebbles, ensuring the pot sits above the water line.
- Group plants together: Clustering plants creates a microclimate with higher humidity.
- Place in a humid room: A well-lit bathroom or kitchen often has higher ambient moisture.
Misting provides only a very temporary boost and is not a substitute for these other methods. Over-misting can sometimes promote fungal issues if the foliage doesn’t dry quickly.
Planting and Potting Mix Fundamentals
Choosing the right container and soil mix sets the foundation for healthy root growth. Selaginella martensii has shallow, fine roots that are susceptible to rot in heavy, waterlogged soil.
Selecting The Right Pot And Drainage
A pot with excellent drainage holes is non-negotiable. Plastic, ceramic, or terracotta pots are all fine, but terracotta wicks away extra moisture, which can be helpful. Because the plant spreads horizontally, a wide, shallow pot or hanging basket often suits its growth habit better than a deep, narrow one.
The Perfect Soil Mix Recipe
The goal is a mix that retains moisture but drains exceptionally well and stays airy. A standard potting soil is too dense on its own.
You can create a suitable mix using:
- 2 parts peat moss or coco coir (for moisture retention)
- 1 part perlite (for aeration and drainage)
- 1 part orchid bark or fine charcoal (for structure and preventing compaction)
A high-quality African violet mix or aroid mix can also be a good commercial alternative, as they are designed for similar moisture-retentive yet well-aerated conditions.
Watering Practices for Healthy Growth
Watering is perhaps the most delicate balancing act with this plant. It wants consistently moist soil but never soggy, waterlogged conditions. The phrase “evenly moist” is key.
How To Check Soil Moisture
Do not water on a strict schedule. Instead, check the soil regularly. Insert your finger about an inch into the soil. If the top inch feels dry to the touch, it’s time to water. The soil should never be allowed to dry out completely, nor should it feel sopping wet.
Watering Technique And Water Quality
Water thoroughly until you see water flow freely from the drainage holes. This ensures the entire root ball is hydrated. Always empty the saucer or cache pot after 15-20 minutes to prevent the plant from sitting in water.
Use room-temperature water. Cold water can shock the roots. If your tap water is very hard or heavily chlorinated, using filtered, distilled, or rainwater is beneficial to prevent tip burn on the leaves.
Fertilizing and Nutritional Needs
Selaginella martensii is not a heavy feeder. Its growth is relatively slow, and over-fertilizing can damage the fine roots and cause leaf burn.
Type And Schedule For Fertilizer
Use a balanced, water-soluble fertilizer (such as a 10-10-10 or 20-20-20 formula) diluted to half the recommended strength. Fertilize only during the active growing season, which is typically spring and summer.
A good rule is to feed once a month from April through September. Do not fertilize in the fall and winter when growth naturally slows. Before applying fertilizer, ensure the soil is already moist to avoid root burn.
Pruning, Propagation, and Maintenance
Regular grooming keeps your plant looking its best and provides material to create new plants. The stems can become long and somewhat tangled over time.
How To Prune For Shape And Health
Use clean, sharp scissors or micro-tip pruners. You can trim back any overly long or straggly stems to maintain a compact, bushy shape. Simply cut just above a leaf node. Regularly remove any stems or leaves that have turned brown or crispy; they will not recover.
Simple Propagation Methods
Propagating Selaginella martensii is straightforward through stem cuttings or division.
Propagation by Stem Cuttings
- Take a healthy stem cutting that is 3-4 inches long.
- Remove the leaves from the bottom inch of the stem.
- Place the cut end into a small pot filled with a moist propagation mix (like the soil mix described earlier).
- Cover the pot with a clear plastic bag to create a humid mini-greenhouse.
- Place in bright, indirect light and keep the soil consistently moist. Roots should develop in a few weeks.
Propagation by Division
When you repot, you can gently tease apart the root ball into smaller sections, each with a good amount of stems and roots. Pot each division separately into appropriately sized containers. This is the quickest way to get a new, established-looking plant.
Troubleshooting Common Problems
Even with good care, issues can arise. Here’s how to diagnose and fix common problems with Selaginella martensii.
Brown, Crispy Leaves Or Tips
This is the most frequent complaint and is almost always related to humidity or water.
- Low humidity: This is the prime suspect. Increase ambient humidity using the methods outlined earlier.
- Underwatering: If the soil dries out completely, the leaves will quickly crisp up. Check your watering frequency and soil moisture.
- Chemical sensitivity: Browning tips can also be a reaction to salts or chemicals in tap water. Try switching to filtered or rainwater.
Yellowing Or Limp Stems
If the stems and leaves are turning yellow and feeling soft or mushy, the issue is likely overwatering and root rot.
- Stop watering immediately.
- Check the roots. Remove the plant from its pot and inspect the root ball. Healthy roots are firm and light-colored. Rotten roots are dark, mushy, and may smell bad.
- Trim away all rotted roots with sterile tools.
- Repot the plant into fresh, well-draining soil and a clean pot.
- Water sparingly until you see new growth, indicating the plant has recovered.
Pests And Diseases
While not extremely prone to pests, it can occasionally attract spider mites, especially in dry air, and mealybugs. Check the undersides of stems and where leaves join the stem for fine webbing or cottony white masses.
Treat infestations promptly by wiping leaves with a cloth dipped in a mild soap and water solution or using an insecticidal soap or neem oil spray, following product instructions. Good humidity helps deter spider mites.
Design Ideas and Companion Planting
With its unique texture and trailing habit, Selaginella martensii is a versatile design element. Its frosted foliage provides a beautiful contrast to plants with solid green, purple, or broad leaves.
Using Frosty Fern In Displays
It works wonderfully as a “spiller” element in mixed container gardens, trailing over the edge of a pot. It is an excellent choice for terrariums or sealed glass gardens, where the high humidity is naturally maintained. You can also grow it in a hanging basket to showcase its cascading stems.
Good Companion Plants
Pair it with other plants that enjoy similar high-humidity, low-light conditions. Some excellent companions include:
- True ferns (like Maidenhair or Bird’s Nest Fern)
- Peperomias
- Pilea
- Small-leaved Philodendrons (like ‘Micans’)
- Fittonia (Nerve Plant)
Avoid pairing it with succulents or cacti, which require completely opposite (dry) conditions.
Frequently Asked Questions
Is Selaginella Martensii Toxic To Pets?
According to the ASPCA, plants in the Selaginella genus are generally considered non-toxic to cats and dogs. However, it’s always best to discourage pets from chewing on any houseplants, as individual animals may have sensitivities.
Why Is My Frosty Fern Losing Its Variegation?
If the white or silvery tips are turning solid green, the plant is not receiving enough bright, indirect light. Move it to a brighter location (without direct sun) to encourage the distinctive frosted new growth to return.
How Often Should I Repot Selaginella Martensii?
Repot every 2-3 years, or when you see roots growing out of the drainage holes. Since it prefers to be slightly root-bound, you don’t need to size up dramatically; moving to a pot just 1-2 inches wider in diameter is sufficient. Spring is the best time to repot.
Can I Grow Selaginella Martensii Outdoors?
In USDA hardiness zones 10-11, it can be grown outdoors in a consistently shaded, protected, and humid spot, such as a covered patio or under dense tree canopy. In most other climates, it is strictly an indoor or seasonal patio plant that must be brought inside well before any threat of frost.
What’s The Difference Between Selaginella Martensii And A True Fern?
While they look similar and have comparable care needs, they are botanically distinct. Selaginella is a spikemoss (a lycophyte), one of the oldest groups of vascular plants. True ferns (pteridophytes) are a younger plant group. The main practical difference is that Selaginella has smaller, scale-like leaves and its stems often have a more trailing or creeping habit compared to many upright ferns.