Repotting guide

When & how to repot Green Cabomba (Cabomba caroliniana)

Also called Green Cabomba, Carolina Fanwort, Green Fanwort, Fish Grass.

More about green cabomba

About Green Cabomba

Cabomba caroliniana · also called Green Cabomba, Carolina Fanwort · tropical

Green Cabomba is a widely cultivated aquarium stem plant from the Americas, forming feathery, bright-green fan-shaped whorls of finely divided leaves. A fast grower in good conditions, it provides excellent oxygenation and spawning cover for fish. It is considered an invasive species in several countries and must never be released into waterways. Not listed as toxic by the ASPCA.

Mature size: Stems 30-80 cm long; pinch tops regularly to maintain compact growth

Watch for — Stems floating free: Cabomba has fragile root anchorage; plant stems in small bunches weighted with plant anchors or thread-tied to small stones initially.

How to tell green cabomba needs repotting

Repotting on a calendar is less reliable than reading the plant. For green cabomba, 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 green cabomba 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 green cabomba

Every 12–18 months — sooner if roots show fast. Green Cabomba's growth habit — fast-growing submersed aquatic stem plant with whorled feathery leaves — sets the pace. Green Cabomba is a widely cultivated aquarium stem plant from the Americas, forming feathery, bright-green fan-shaped whorls of finely divided leaves. A fast grower in good conditions, it provides excellent oxygenation and spawning cover for fish. It is considered an invasive species in several countries and must never be released into waterways. Not listed as toxic by the ASPCA.

What size pot to step green cabomba up to

Step up one pot size — about 2–3 cm (an inch) wider. Green Cabomba 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 green cabomba

Early spring, just as new growth restarts, is the ideal window for green cabomba. 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 green cabomba

Time it for spring. Repot green cabomba 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 green cabomba out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh fine-grain aquarium gravel or planted-tank substrate 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 green cabomba 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 green cabomba

Green Cabomba wants fine-grain aquarium gravel or planted-tank substrate. Plant stems in groups of 5-7 in fine substrate, anchoring 3-4 cm deep. The root system is delicate; avoid disturbance once established. Root tabs provide additional nutrition but liquid fertiliser in the water column is often sufficient for this moderate feeder. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting green cabomba — frequently asked questions

How often should you repot green cabomba?

Every 12–18 months — sooner if roots show fast for green cabomba. Repot green cabomba 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 fine-grain aquarium gravel or planted-tank substrate. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does green cabomba need?

When is the best time of year to repot green cabomba?

Can you put green cabomba straight into a much bigger pot?

No. Even a fast-growing green cabomba 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 green cabomba after repotting?

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