Repotting guide

When & how to repot Crimson Cestrum (Cestrum elegans)

Also called Crimson Cestrum, Purple Cestrum, Elegant Jessamine.

More about crimson cestrum

About Crimson Cestrum

Cestrum elegans · also called Crimson Cestrum, Purple Cestrum · tropical

Crimson Cestrum is a vigorous, arching evergreen shrub prized for its drooping clusters of deep crimson to purple-red tubular flowers produced from summer through autumn, followed by dark red berries. It thrives in full sun to partial shade in sheltered, well-draining soil. All parts are toxic. RHS hardiness H3 — suitable for mild UK gardens or cool glasshouses.

Mature size: 2–3 m tall (6–10 ft), spread 1.5–2 m (5–6 ft) in open ground; more compact in containers or with regular pruning

How to tell crimson cestrum needs repotting

Repotting on a calendar is less reliable than reading the plant. For crimson cestrum, 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 crimson cestrum 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 crimson cestrum

Every 12–18 months — sooner if roots show fast. Crimson Cestrum's growth habit — upright to arching, vigorous evergreen shrub; can be wall-trained — sets the pace. Crimson Cestrum is a vigorous, arching evergreen shrub prized for its drooping clusters of deep crimson to purple-red tubular flowers produced from summer through autumn, followed by dark red berries. It thrives in full sun to partial shade in sheltered, well-draining soil. All parts are toxic. RHS hardiness H3 — suitable for mild UK gardens or cool glasshouses.

What size pot to step crimson cestrum up to

Step up one pot size — about 2–3 cm (an inch) wider. Crimson Cestrum 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 crimson cestrum

Early spring, just as new growth restarts, is the ideal window for crimson cestrum. 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 crimson cestrum

Time it for spring. Repot crimson cestrum 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 crimson cestrum out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh rich, well-draining loam 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 crimson cestrum 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 crimson cestrum

Crimson Cestrum wants rich, well-draining loam. Performs best in fertile, humus-rich, well-draining loam or loamy sand. In containers, a loam-based compost such as John Innes No. 3 mixed with added perlite is recommended by the RHS. Tolerates loam, sand, and chalk-based soils; prefers a pH of 6.0–7.5. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting crimson cestrum — frequently asked questions

How often should you repot crimson cestrum?

Every 12–18 months — sooner if roots show fast for crimson cestrum. Repot crimson cestrum 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 rich, well-draining loam. Don't jump several sizes — that soggy excess soil is what rots vigorous roots.

What size pot does crimson cestrum need?

When is the best time of year to repot crimson cestrum?

Can you put crimson cestrum straight into a much bigger pot?

No. Even a fast-growing crimson cestrum 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 crimson cestrum after repotting?

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