Emerald Spike Moss (Martens' spikemoss) care

Light

The Goldilocks zone. Not the south-facing windowsill (too hot, too direct), not the back of the room (too dim, growth stalls). Medium to low indirect light, like a shaded forest floor. Direct sun scorches and bleaches the fronds within hours, so keep it out of unfiltered windows; a north or east aspect or a spot a metre back from brighter glass works well. If you can't decide, a free phone lux-meter app aimed at the leaf at noon should read between 800 and 1,500 lux.

Watering

Watering emerald spike moss: keep the soil consistently, evenly moist — never let it dry out. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. This is a thirsty plant that will not recover well from drought; the soil should stay damp like a wrung sponge but never waterlogged. Water from below or use soft, lime-free water (rain or distilled), as it dislikes hard tap water. Let only the very top surface dry between waterings, and reduce slightly in winter.

Soil and pot

Emerald Spike Moss grows best in moisture-retentive, peat-free, slightly acidic mix. A water-retaining but free-draining mix suits it best: coir or peat-free compost lightened with perlite and a little fine bark, at roughly pH 5.5-6.5. The blend must hold moisture without going stagnant. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Emerald Spike Moss sits happiest at around 60-80%+ humidity and 18-24°C (65-75°F). High humidity is non-negotiable — this is the single hardest part of its care. Below about 50% the fine foliage browns and crisps quickly. A closed or open terrarium, propagation case, or grouping with a humidifier is strongly recommended over an open shelf. If you keep the room above 18 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed emerald spike moss sparingly. Feed lightly with a balanced liquid houseplant fertiliser diluted to half or quarter strength, roughly monthly during spring and summer. Spikemosses are sensitive to fertiliser salts, so flush occasionally and stop feeding in autumn and winter. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on emerald spike moss in the Growli community. Each is annotated with the most common cause so you know where to start.

• Brown, crispy frond tips — Almost always low humidity or air that is too dry — the most common failure with this species; raise humidity well above 50%.
• Whole plant browning and shrivelling — The soil was allowed to dry out; spikemoss does not tolerate drought and rarely bounces back fully, so keep it evenly moist.
• Bleached or scorched foliage — Too much direct sun stresses and yellows the leaves; move to medium or low indirect light.
• Yellowing leaves and mushy base — Overwatering or stagnant, waterlogged soil leading to root rot; ensure the mix drains even though it stays moist.
• Browning despite damp soil — Often hard or chlorinated tap water; switch to rainwater, filtered, or distilled water.
• Leggy, thin, open growth — Insufficient light or very low humidity; improve both and pinch back to encourage a denser, bushier habit.

Propagation

Easiest by division or stem cuttings in spring: lift and split the clump into sections each with roots, or lay short stem pieces on moist mix and keep them under high humidity (a covered tray or terrarium) until they root. It can also be grown from spores, but this is slow and far less practical for home growers. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Emerald Spike Moss is pet-safe. Selaginella martensii is not individually listed in the ASPCA toxic and non-toxic plant database, but the genus is clean: the ASPCA lists Selaginella kraussiana (Club Moss) as non-toxic to dogs, cats, and horses, and no Selaginella species is listed as toxic. It is therefore considered pet-safe, but verify with your vet for your specific pet. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Emerald Spike Moss deep-dive guides

Every aspect of emerald spike moss care, each with its own calibrated guide:

• Emerald Spike Moss watering schedule
• Emerald Spike Moss light requirements
• Best soil mix for emerald spike moss
• Emerald Spike Moss fertilizing guide
• When to repot emerald spike moss
• How to propagate emerald spike moss
• Emerald Spike Moss growth rate & size
• Emerald Spike Moss cold hardiness
• Emerald Spike Moss temperature & humidity
• Is emerald spike moss toxic to cats & dogs?

Related guides

Emerald Spike Moss is also known as Martens' spikemoss, emerald spikemoss, variegated spikemoss, Martens club moss, and frosty fern (when silver-tipped).

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