Repotting guide

When & how to repot Reunion Island Begonia (Begonia salaziensis)

Also called Reunion Island begonia, Salazie begonia.

More about reunion island begonia

About Reunion Island Begonia

Begonia salaziensis · also called Reunion Island begonia, Salazie begonia · tropical

Begonia salaziensis is a rare fibrous-rooted species endemic to the cloud-forest habitats of Réunion Island in the Indian Ocean, where it grows as an understorey plant in cool, misty conditions. It produces attractive foliage and small pink to white flowers, preferring consistently cool temperatures that distinguish it from most tropical begonias. The single most critical care point is to keep temperatures below 25 °C, as prolonged heat causes rapid decline in this naturally cool-adapted species. This plant is toxic to cats and dogs.

Mature size: 25–40 cm tall and 20–30 cm wide.

Watch for — Powdery mildew: Poor air circulation combined with low light encourages powdery mildew on the leaves; improve airflow, avoid overhead watering, and treat early infections with a dilute potassium bicarbonate spray.

How to tell reunion island begonia needs repotting

Repotting on a calendar is less reliable than reading the plant. For reunion island begonia, 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 reunion island begonia 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 reunion island begonia

Every 12–18 months — sooner if roots show fast. Reunion Island Begonia's growth habit — compact, upright fibrous-rooted perennial with a tidy bushy form. — sets the pace. Begonia salaziensis is a rare fibrous-rooted species endemic to the cloud-forest habitats of Réunion Island in the Indian Ocean, where it grows as an understorey plant in cool, misty conditions. It produces attractive foliage and small pink to white flowers, preferring consistently cool temperatures that distinguish it from most tropical begonias. The single most critical care point is to keep temperatures below 25 °C, as prolonged heat causes rapid decline in this naturally cool-adapted species. This plant is toxic to cats and dogs.

What size pot to step reunion island begonia up to

Step up one pot size — about 2–3 cm (an inch) wider. Reunion Island Begonia 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 reunion island begonia

Early spring, just as new growth restarts, is the ideal window for reunion island begonia. 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 reunion island begonia

Time it for spring. Repot reunion island begonia 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 reunion island begonia out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh humus-rich, free-draining compost 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 reunion island begonia 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 reunion island begonia

Reunion Island Begonia wants humus-rich, free-draining compost. Mix three parts peat-free compost with one part perlite and one part fine bark; the mix should retain some moisture while draining freely to prevent root rot. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting reunion island begonia — frequently asked questions

How often should you repot reunion island begonia?

Every 12–18 months — sooner if roots show fast for reunion island begonia. Repot reunion island begonia 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 humus-rich, free-draining compost. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does reunion island begonia need?

When is the best time of year to repot reunion island begonia?

Can you put reunion island begonia straight into a much bigger pot?

No. Even a fast-growing reunion island begonia 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 reunion island begonia after repotting?

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