Carob

How to recognise it

Habit

Evergreen tree of 5–10 m with a short, thick trunk and a broad, rounded crown. In a pot in Belgium usually 1–3 m.

Leaf

Pinnate, 10–20 cm, without a terminal leaflet, with 2–5 pairs of round to oval, leathery leaflets of 3–7 cm; glossy dark green above, paler below.

Flower

Small flowers without petals, greenish to reddish, in short spikes straight from old wood and the trunk, in September–November. They have a heavy, rather odd smell. Most trees are either male or female.

Fruit

A flat, leathery pod of 10–25 cm, green at first, dark brown when ripe, with sweet pulp and 10–15 hard, shiny seeds. The pods only ripen about a year after flowering.

Bark

Grey-brown, rough and cracked on older trees.

Look-alikes

Honey locust (Gleditsia triacanthos) also has long, flat, brown pods, but it is deciduous, has finely divided leaves with many small leaflets and often long thorns. The mastic tree (Pistacia lentiscus) also has pinnate, leathery leaves, but small, round fruits in clusters.

Flowering: September–November · Pruning: March

Why grow it?

• An evergreen container plant with glossy, leathery leaves that brings a Mediterranean feel all year round.
• Copes very well with drought and heat: ideal for a sunny, warm patio.
• Grows slowly and stays compact in a pot for years.
• A plant with a story: its seeds gave their name to the carat, and the pods were already eaten in ancient times, by people and animals alike.
• In its home range it flowers in autumn and provides nectar and pollen for bees and flies, at a time when little else is in flower.

Carob: where does it grow best?

• Wild and naturalised on dry, rocky slopes and in the maquis around the Mediterranean, often on limestone and near the coast, where it rarely freezes.
• In Belgium as a container plant: outdoors from mid-May to October in the sunniest, warmest spot, for example on a south-facing patio.
• In a large pot of free-draining compost mixed with a third of grit or coarse sand; a drainage hole is essential.
• Indoors in winter: light, cool (5–10 °C) and frost-free, for example in an unheated greenhouse or a cool, bright room.
• Planting out in open ground only works in a very sheltered spot in a mild city or on the coast, and even then it is often lost after a hard winter.

Goes well with

• Olive: Another Mediterranean container plant that needs the same sun, dry conditions and winter quarters.
• Rosemary: Fragrant and drought-tolerant, with blue flowers in spring for the first bees.
• Lavender: Flowers in summer and draws bees and butterflies to the patio.
• Bay laurel: An evergreen container plant that tolerates a little more frost: together a truly Mediterranean patio.

Carob: when and how to plant it?

1. Buy a young plant in a pot from a nursery or garden centre that sells Mediterranean plants.
2. Or sow your own: nick the hard seed coat with a file, or pour hot water over the seeds and let them soak for 24 hours. Sow in March–April at 20–25 °C, one seed per deep pot; they germinate within a few weeks.
3. Pot young plants on into a deeper pot in good time: they quickly form a long taproot.
4. For an older plant, choose a sturdy pot of at least 40 cm, with a layer of gravel at the bottom.
5. Put it outside after mid-May, the first week in partial shade, so that the leaves can get used to the bright sun.
6. Never bring home plants or seedlings taken from the wild on holiday: buy them from a nursery.

Care

Watering

In summer, only water when the top few centimetres of compost are dry, then water thoroughly. In winter very little: just enough to stop the rootball drying out.

Feeding

From April to August, a little organic feed for container plants every three to four weeks; after that, none.

Overwintering

Light and cool, at 5–10 °C. Bring it in before the first night frost, usually in October.

Repotting

Every two to three years in March, into a slightly larger pot. For a large plant, replace the top layer of compost instead.

Moving outside

After mid-May, when there are no more night frosts; let it get used to full sun gradually.

Tip: Overwinter it as light and cool as possible, but frost-free: an unheated greenhouse is ideal. Warmth and darkness in winter are its worst enemies.

Pruning and mowing

Pruning months: March.

When: In March, before it goes back outside. It grows slowly, so pruning is rarely needed.

How:

• Remove dead, weak and crossing branches.
• Shorten overlong branches to just above a leaf, to keep the crown compact and balanced.
• For a standard, gradually remove the lowest side branches.

Caution: Flowers and pods grow on old wood, even on the trunk: do not saw off thick, old branches if you are hoping for flowers.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Nick the hard seed coat, or soak the seeds for 24 hours after pouring hot water over them. Sow in March–April at 20–25 °C in deep pots. Seedlings only flower after many years, and you cannot tell in advance whether they will be male or female.

Cuttings and grafting

Semi-ripe cuttings in summer with bottom heat root poorly. Nurseries graft female varieties onto seedlings; that is a job for a professional.

Carob: how does it get through the winter?

Hardy to −5 °C: protect in harsh winters.

• Not hardy: an old tree in open ground briefly tolerates about −5 °C, a pot plant much less, because its roots freeze.
• Evergreen: it keeps its leaves in winter quarters if it gets enough light.
• Overwintering too warm and too dark causes leaf drop and weak shoots; too wet causes root rot.
• In winter, check regularly for scale insects and mealybugs.

Diseases and pests

• Scale insects: Brown scales on stems and leaves and sticky honeydew, especially in winter quarters. Wipe them off with a soft brush or a cloth dipped in lukewarm water with a little soft soap.
• Mealybugs: White, woolly tufts in the leaf axils. Wipe them off with a cotton bud; overwintering light and cool helps.
• Root rot: Yellow leaves and wet, musty compost. Water less and use a pot with a drainage hole and coarse, free-draining compost.
• Leaf drop in winter: Caused by too little light or too much warmth. Move it somewhere lighter and cooler; it usually regrows in spring.

Through the year

• January: Winter quarters: light, cool and frost-free. Very little water.
• February: Check for scale insects and mealybugs.
• March: Prune and repot if needed. Sow indoors at 20–25 °C.
• April: Water a little more. Start feeding.
• May: After mid-May, move outside, the first week in partial shade.
• June: In the sunniest spot. Water when the surface is dry.
• July: Water and feed.
• August: Last feed of the year.
• September: Older plants may flower, with small reddish clusters on the old wood.
• October: Older plants in flower. Bring indoors before the first night frost.
• November: Winter quarters: little water, light and cool.
• December: Rest in winter quarters.

Did you know?

• The word carat comes, via Arabic, from the Greek keration, the name for the carob seed, which was once used as a weight for gemstones and gold. The idea that the seeds all weigh exactly the same is a myth, though: they vary as much as other seeds.
• According to an old interpretation, John the Baptist did not eat locusts in the desert but the pods of this tree: hence the names St John’s bread and locust bean. The prodigal son in the biblical parable also longed to eat the pods fed to the pigs.
• Locust bean gum (E 410), a thickener used in ice cream and sauces among other things, is made from the seeds; the ground pods are used as a substitute for cocoa.