Repotting guide

When & how to repot Carob (Ceratonia siliqua)

Also called Carob, Locust bean, St John's bread.

More about carob

About Carob

Ceratonia siliqua · also called Carob, Locust bean · tropical

Carob is a tough Mediterranean evergreen tree producing sweet brown pods used as a cocoa substitute and animal feed. Highly drought- and heat-tolerant, it thrives in full sun and poor, free-draining soil, and tolerates coastal and dry conditions. It is frost-tender when young but hardy to light frost once established. Slow-growing, long-lived and often dioecious, needing a male for pods.

Mature size: 8-15 m tall and wide at maturity; can be kept much smaller in large containers but pods less reliably when confined.

Watch for — Root rot from overwatering: The commonest killer, especially in pots or heavy soils; water deeply but infrequently and ensure very sharp drainage.

How to tell carob needs repotting

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

Thick roots out of the drainage holes, or circling the surface and lifting the plant.
The pot dries out unusually fast and carob wilts between waterings it used to shrug off.
The plant is visibly top-heavy and tips over easily.
Stalled growth and small new leaves over a full season — though with a big specimen, top-dressing is often the better first response before a full 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 carob

Every 2–3 years; top-dress in the in-between years. Carob's growth habit — slow-growing, long-lived evergreen tree with a broad domed canopy, dark glossy pinnate leaves and pendent leathery pods; usually dioecious, so both sexes are needed for a pod crop. — sets the pace. Carob is a tough Mediterranean evergreen tree producing sweet brown pods used as a cocoa substitute and animal feed. Highly drought- and heat-tolerant, it thrives in full sun and poor, free-draining soil, and tolerates coastal and dry conditions. It is frost-tender when young but hardy to light frost once established. Slow-growing, long-lived and often dioecious, needing a male for pods.

What size pot to step carob up to

Move up exactly one pot size. A heavy carob dropped into a vastly bigger pot sits in a reservoir of wet soil its roots cannot reach, which rots them and destabilises the plant. In the years between repots, lift off and replace the top 3–5 cm of soil (top-dressing) instead — it refreshes nutrients without the shock of a full repot.

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 carob

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

Consider top-dressing first. If carob is not badly root-bound, scrape off and replace the top 3–5 cm of soil instead — far less shock for a big plant that hates moving.
Get help and one size up. For a full repot, choose a pot just one size larger. A heavy plant needs two people and a stable, free-draining pot.
Ease it out on its side. Lay the plant down, slide the pot off, and gently loosen the outer roots. Do not bare-root a mature specimen.
Repot at the same depth. Add fresh poor, dry, free-draining alkaline soil beneath and around the rootball, keeping the original soil line. Firm it so the trunk is stable and upright.
Water and leave it put. Water thoroughly, then leave carob in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave carob in exactly the same spot and light it was in before — moving and repotting at the same time is what makes a big specimen drop leaves. Water it in well, then let the top of the soil dry before watering again so the larger volume of fresh soil does not stay sodden. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for carob

Carob wants poor, dry, free-draining alkaline soil. Thrives on lean, rocky, sandy or limestone soils and tolerates alkalinity and salt (pH 6.5-8.5). Sharp drainage is critical; avoid rich, heavy or waterlogged ground. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting carob — frequently asked questions

How often should you repot carob?

Every 2–3 years; top-dress in the in-between years for carob. Fully repot carob only every 2–3 years; in the in-between years just top-dress the top 3–5 cm of soil. Step up one pot size in spring with poor, dry, free-draining alkaline soil. It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does carob need?

When is the best time of year to repot carob?

Should you top-dress or fully repot carob?

For a big, heavy carob, top-dressing — replacing the top 3–5 cm of soil — is the gentler option most years, with a full repot only every 2–3 years. A mature specimen sulks and drops leaves when fully repotted, so do it as rarely as the roots allow.

Should you fertilise carob after repotting?

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