Repotting guide

When & how to repot Spike Moss (Selaginella apoda)

Also called Meadow Spikemoss, Creeping Selaginella.

More about spike moss

About Spike Moss

Selaginella apoda · also called Meadow Spikemoss, Creeping Selaginella · houseplant

Selaginella apoda is a low-growing, mat-forming spikemoss native to eastern North America, with delicate bright-green scale-like leaves. It thrives in moist, shaded terrariums or humid windowsills. Not a true moss or fern, but similarly considered non-toxic, with no ASPCA listings indicating harm.

Mature size: 2-5 cm tall, spreading indefinitely as ground cover

Watch for — Fungal rot: In overly wet, stagnant conditions rot can set in. Ensure air circulation and avoid standing water around the root zone.

How to tell spike moss needs repotting

Repotting on a calendar is less reliable than reading the plant. For 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 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 spike moss

Every 12–18 months — sooner if roots show fast. Spike Moss's growth habit — low-growing creeping mat-former — sets the pace. Selaginella apoda is a low-growing, mat-forming spikemoss native to eastern North America, with delicate bright-green scale-like leaves. It thrives in moist, shaded terrariums or humid windowsills. Not a true moss or fern, but similarly considered non-toxic, with no ASPCA listings indicating harm.

What size pot to step spike moss up to

Step up one pot size — about 2–3 cm (an inch) wider. 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 spike moss

Early spring, just as new growth restarts, is the ideal window for 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 spike moss

Time it for spring. Repot 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 spike moss out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh moist, fine-textured peat-free mix with high organic content 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 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 spike moss

Spike Moss wants moist, fine-textured peat-free mix with high organic content. A mix of coir, fine bark, and perlite at roughly 2:1:1 provides the moist, slightly acidic substrate this species requires. Avoid sandy or fast-draining mixes. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting spike moss — frequently asked questions

How often should you repot spike moss?

Every 12–18 months — sooner if roots show fast for spike moss. Repot 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 moist, fine-textured peat-free mix with high organic content. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does spike moss need?

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

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

No. Even a fast-growing 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 spike moss after repotting?

Not immediately. Wait about 4 weeks after repotting 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.