Repotting guide

When & how to repot Colocasia Fontanesii (Colocasia esculenta 'Fontanesii')

Also called violet-stemmed taro, black-stemmed taro.

More about colocasia fontanesii

About Colocasia Fontanesii

Colocasia esculenta 'Fontanesii' · also called violet-stemmed taro, black-stemmed taro · tropical

Colocasia esculenta 'Fontanesii' is the violet-stemmed taro, with large drooping green leaves on striking dark purple-black stems and veining. A vigorous, moisture-loving clumping aroid, it wants bright light, abundant water, warmth, and rich soil, and even thrives in boggy conditions. Bold and fast-growing, but toxic to pets and people like all Colocasia.

Mature size: Commonly 1.2-1.8 m tall and spreading widely in a single season under warm, wet, fertile conditions.

How to tell colocasia fontanesii needs repotting

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

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for colocasia fontanesii) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

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 colocasia fontanesii

Only every 2–4 years, when genuinely crowded. Colocasia Fontanesii is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. A fast, vigorous clumping perennial that spreads by stolons and tubers, sending up large drooping leaves on tall dark stems and forming substantial colonies in warm, wet conditions..

What size pot to step colocasia fontanesii up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Colocasia Fontanesii positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping colocasia fontanesii into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

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 colocasia fontanesii

Early spring, just as new growth restarts, is the ideal window for colocasia fontanesii. 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 colocasia fontanesii

Confirm it actually needs it. Slide colocasia fontanesii out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip colocasia fontanesii out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh rich, moisture-retentive soil, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water colocasia fontanesii again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for colocasia fontanesii

Colocasia Fontanesii wants rich, moisture-retentive soil. Use a heavy, fertile, humus-rich mix that holds plenty of water; this is one aroid that welcomes dense, wet soil. It also grows happily as a marginal aquatic in containers without drainage holes. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting colocasia fontanesii — frequently asked questions

How often should you repot colocasia fontanesii?

Only every 2–4 years, when genuinely crowded for colocasia fontanesii. Only repot colocasia fontanesii every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using rich, moisture-retentive soil. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does colocasia fontanesii need?

When is the best time of year to repot colocasia fontanesii?

Does colocasia fontanesii like to be root-bound?

Yes — colocasia fontanesii genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise colocasia fontanesii after repotting?

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