Posted by Phytopath on Mar 24, 2010
Also known as St. John’s bread, but the botanical name Ceratonia siliqua L., derives from Greek keras, horn and Latin siliqua, alluding to the hardness and shape of the pod.
The carob is an evergreen, long lived, medium sized tree, growing to about ten metres high and wide. It is densely branched making it an ideal shade tree and it suffers little from pest and disease problems.
The tree is relatively slow growing, reaching about seven metres in ten years in my climate. The carob is thought to be native to the Eastern Mediterranean region and it grows well in all countries bordering the Mediterranean Sea.
The carob tree has similar temperature requirements to that of citrus but demands much less water, it is more tender than the olive and its rooting habit is similar to pistachio, meaning the root system is extensive and penetrates deeply into the soil, reportedly up to 20 metres [wow].
Soil requirements for good growth are well drained deep sandy loams but the tree will grow in other soil types as long as they are not waterlogged. Soil type will affect tree size and productivity.
The main growth periods are spring and autumn with growth slowing down once the temperature falls below 10 °C but if the tree is grown in favourable warm conditions, growth does not slow down.
The carob tree is a xerophyte meaning it can survive in very dry climates with an annual rainfall of 250 mm per year. Of course bean production will increase if the rainfall is around 500 mm per annum, or if the tree is irrigated.
Ceratonia siliqua is in the Legume family (same as peas & beans) but interestingly does not nodulate and therefore is unable to fix nitrogen like other legumes. There is however, an association with a mycorrhizal fungi, which can improve general nutrition levels to the tree.
Carob is dioecious with some hermaphroditic forms, meaning that male and female flowers occur on separate trees (just like kiwi fruit). So if you want a good crop of beans you will need a male and a female tree, although there are some hermaphrodite varieties available.
Areas suitable for planting carob would have cool but not cold winters (trees are damaged when temperatures fall below 4°C), mild to warm springs and warm to hot dry summers (sounds like my place). These climatic conditions would occur in areas of the northern hemisphere between latitudes 30° to 45° and in the southern hemisphere between 30° and 40°.
Winter chilling is not required for fruit set but temperatures above 9°C for 5000 to 6000 hours are needed for the pods to ripen. Rain in autumn can also interfere with pollination and have an adverse affect on fruit set. The pods ripen in autumn and are harvested shortly after. Top yielding commercial trees can produce 1 tonne of beans.
Pods (without the seed) can be eaten fresh or ground into a powder after drying. They are an excellent source of dietary fibre (supposedly as much as wheat bran) and pectin, a beneficial fibre that helps the elimination of toxins. The pods also contain many of the B group vitamins as well as minerals, especially calcium. Some sources quote “twice as much calcium as whole milk”.
The carob flour can be used to flavour confectionary, yoghurt, cereals and coffee. It is naturally sweet and prized as a health food. If stored in a cool, dry, dark place, the flour will keep for up to one year.
The seeds (not the pods) are very hard and uniform in weight. All pods weigh almost exactly one carat each (200 mg) which is still the standard measure for gold and precious stones.