Repotting guide

When & how to repot Crocodile fern (Microsorum musifolium)

Also called alligator fern, crocodile leaf fern.

About Crocodile fern

Microsorum musifolium · also called alligator fern, crocodile leaf fern · houseplant

Crocodile fern is a tropical Asian fern with broad strap leaves marked with a striking dark crocodile-skin pattern. Pet-safe and prefers high humidity. Easier than maidenhair fern but still needs consistent moisture.

Microsorum musifolium, an epiphytic fern native from southern Myanmar through Indonesia, Borneo and New Guinea, growing on rainforest tree trunks and branches, not in ground soil.

A rich, moist, well-drained organic mix that drains freely around the surface-creeping rhizome; an orchid or epiphyte blend suits its rootball well.

Mature size: 60-90 cm tall and wide

Sources: plants.ces.ncsu.edu, missouribotanicalgarden.org

How to tell crocodile fern needs repotting

Repotting on a calendar is less reliable than reading the plant. For crocodile fern, watch for these signs:

Roots creeping out of the drainage holes or matting tightly across the soil surface.
The rootball dries out within a day or two no matter how much you water.
Water channels straight down the gap between rootball and pot without wetting the centre.
Steady decline — thin growth, persistent crispy edges — that good humidity and watering have not fixed. Only then is the disturbance of a repot worth the risk for crocodile fern.

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 crocodile fern

Every 1–2 years, disturbing the roots as little as possible. Crocodile fern's growth habit — clumping epiphytic fern — sets the pace. Crocodile fern is a tropical Asian fern with broad strap leaves marked with a striking dark crocodile-skin pattern. Pet-safe and prefers high humidity. Easier than maidenhair fern but still needs consistent moisture.

What size pot to step crocodile fern up to

Go up only one size and handle the rootball as little as possible. Crocodile fern resents root disturbance, so the goal is to slide the intact rootball into slightly more soil — not to tease, wash or prune the roots. A modest step up means less shock and a faster recovery.

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 crocodile fern

Early spring, just as new growth restarts, is the ideal window for crocodile fern. 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 crocodile fern

Keep disturbance to a minimum. Crocodile fern resents root disturbance, so the plan is to move the intact rootball — not to wash, tease or prune the roots.
Choose just one size up. Pick a pot only one size larger with drainage, and have moisture-retentive rich free-draining mix ready.
Slide the rootball out whole. Water the day before, then ease crocodile fern out keeping the rootball intact. Gently free only the roots that are circling the very bottom.
Nestle it into fresh soil. Add a base layer of fresh mix, set the rootball in at the same depth, and backfill gently around the sides without packing hard.
Water and protect. Water in, then keep it warm, humid and out of direct sun for a few weeks while it re-roots. Expect a short sulk — that is normal.

Aftercare

Expect crocodile fern to sulk for a couple of weeks — that is normal after any root disturbance for this group. Keep it warm, humid and out of direct sun, water just enough to keep the mix lightly moist, and do not panic and overwater while it re-roots. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for crocodile fern

Crocodile fern wants rich free-draining mix. Compost with orchid bark and perlite for aeration. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting crocodile fern — frequently asked questions

How often should you repot crocodile fern?

Every 1–2 years, disturbing the roots as little as possible for crocodile fern. Repot crocodile fern every 1–2 years, disturbing the roots as little as possible — it sulks for weeks if the rootball is teased apart. Slide it into one size up in spring with fresh rich free-draining mix, keep it warm and humid afterwards, and never bare-root or hard-prune the roots.

What size pot does crocodile fern need?

When is the best time of year to repot crocodile fern?

Why does crocodile fern sulk after repotting?

Crocodile fern resents root disturbance, so a wilt or stall for a week or two after repotting is normal, not a failure. Minimise it by keeping the rootball intact, stepping up just one size, and keeping the plant warm, humid and out of direct sun while it re-roots.

Should you fertilise crocodile fern after repotting?

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