Repotting guide

When & how to repot Spreading Spike Moss (Selaginella kraussiana)

Also called Krauss's Spike Moss, Mat Spikemoss, Trailing Spike Moss.

More about spreading spike moss

About Spreading Spike Moss

Selaginella kraussiana · also called Krauss's Spike Moss, Mat Spikemoss · houseplant

Spreading Spike Moss is a fast-growing, mat-forming spike moss native to the Azores, Canary Islands, and parts of Africa, widely naturalised in many warm-temperate regions. Its bright emerald-green, moss-like foliage spreads readily across moist soil. Ideal for terrariums and humid shelves. Not toxic to cats and dogs.

Mature size: 2-5 cm tall, spreading indefinitely across moist surfaces

Watch for — Root rot: While it needs constant moisture, waterlogged soil causes rot. Ensure the growing medium is moist but well-aerated, not sodden.

How to tell spreading spike moss needs repotting

Repotting on a calendar is less reliable than reading the plant. For spreading spike moss, watch for these signs:

Roots poking out of the drainage holes or coiling visibly around the inside of the pot.
You are watering far more often than you used to because the rootball dries out within a day or two.
Water runs straight through and out the bottom without soaking in.
Top growth has slowed or new spreading spike moss leaves are noticeably smaller than older ones despite good light.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot spreading spike moss

Every 12–18 months — sooner if roots show fast. Spreading Spike Moss's growth habit — prostrate, mat-forming spike moss spreading vigorously across moist substrates — sets the pace. Spreading Spike Moss is a fast-growing, mat-forming spike moss native to the Azores, Canary Islands, and parts of Africa, widely naturalised in many warm-temperate regions. Its bright emerald-green, moss-like foliage spreads readily across moist soil. Ideal for terrariums and humid shelves. Not toxic to cats and dogs.

What size pot to step spreading spike moss up to

Step up one pot size — about 2–3 cm (an inch) wider. Spreading Spike Moss grows fast, so it will fill that space within a season, but jumping several sizes at once still backfires: the unused soil stays soggy and rots even a vigorous root system. One size at a time, every year or so, is the rhythm.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot spreading spike moss

Early spring, just as new growth restarts, is the ideal window for spreading spike moss. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting spreading spike moss

Time it for spring. Repot spreading spike moss in early spring as growth restarts so it re-roots quickly into the fresh soil.
Choose one size up. Pick a pot about 2–3 cm wider with drainage holes. One step only — a much bigger pot stays soggy and rots roots.
Ease the plant out. Water lightly the day before, then tip spreading spike moss out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh moisture-retentive, peat-free mix high in organic matter in the new pot, set the plant so its soil line is unchanged, and backfill, firming lightly.
Water and pause feeding. Water once to settle the soil. Hold off fertiliser for about a month — fresh mix already has nutrients and feeding now burns new roots.

Aftercare

Water spreading spike moss once to settle the soil, then let the surface dry before watering again — fresh mix around the roots stays wetter than the old compacted ball, so the commonest post-repot mistake is overwatering. Keep it out of direct sun for a week or two while roots re-establish. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for spreading spike moss

Spreading Spike Moss wants moisture-retentive, peat-free mix high in organic matter. Use a mix of fine coco coir, leaf mould, and a little perlite. The mix should hold moisture while still allowing some air to the roots. Slightly acidic pH (5.5-6.5) is optimal. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting spreading spike moss — frequently asked questions

How often should you repot spreading spike moss?

Every 12–18 months — sooner if roots show fast for spreading spike moss. Repot spreading spike moss roughly every 12–18 months, in early spring as growth restarts. It grows fast and circles its pot quickly, so step up one size (about 2–3 cm wider) into fresh moisture-retentive, peat-free mix high in organic matter. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does spreading spike moss need?

When is the best time of year to repot spreading spike moss?

Can you put spreading spike moss straight into a much bigger pot?

No. Even a fast-growing spreading spike moss should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise spreading spike moss after repotting?

Not immediately. Wait about 4 weeks after repotting spreading spike moss. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.