The Carob tree (from Arabic: خروب "kharūb" and Hebrew: חרוב Charuv), Ceratonia siliqua, is a leguminous evergreen shrub or tree of the family Leguminosae (pulse family) native to the Mediterranean region. It is cultivated for its edible seed pods. Carobs are also known as St. John's bread. According to tradition of some Christians, St. John the Baptist subsisted on them in the wilderness. A similar legend exists of Rabbi Shimon bar Yochai and his son.
A traditional food plant in Africa, this little-known fruit has potential to improve nutrition, boost food security, foster rural development and support sustainable landcare.
Most carob trees are dioecious. The trees blossom in autumn (September-October). The flowers are small and numerous, spirally arranged along the inflorescence axis in catkin-like racemes borne on spurs from old wood and even on the trunk (cauliflory); they are pollinated by both wind and insects. Male flowers produce a characteristic odour, resembling semen. The fruit is a pod which can be elongated, compressed, straight or curved, and thickened at the sutures. The pods take a full year to develop and ripen. The ripe pods eventually fall to the ground and are eaten by various mammals, thereby dispersing the seed.
The Carob genus Ceratonia belongs the Leguminosae (Legume) family, and is believed to be an archaic remnant of a part of this family now generally considered extinct. It grows well in warm temperate and subtropical areas and tolerates hot and humid coastal areas. As a xerophytic (drought-resistant) species, Carob is well adapted to the ecological conditions of the Mediterranean region. Trees prefer well drained loams and are intolerant of waterlogging, but the deep root systems can adapt to a wide variety of soil conditions and are fairly salt-tolerant.
While previously not believed to form nitrogen fixation nodules typical of the Legume family, more recently trees have been identified with nodules containing bacteria believed to be from the Rhizobium genus.
Although used extensively for agriculture, Carob can still be found growing wild in eastern Mediterranean regions and has become naturalized in the west. The carob tree is typical in the southern Portuguese region of the Algarve, where it has the name alfarrobeira (for the tree), and alfarroba (for the fruit), as well as in southern Spain (algarrobo, algarroba), Malta (Ħarruba), on the Italian islands of Sicily and Sardinia (carrubo, carruba), and in Southern Greece as well as many Greek islands such as Crete and Samos. The common Greek name is Charoupia ,[Ελληνικά: χαρουπιά]. In Turkey, it is known as "keçiboynuzu", meaning "goat's horn". The various trees known as algarrobo in Latin America (Hymenaea courbaril in Colombia and four kinds of Prosopis in Argentina and Paraguay) belong to a different family, the Cesalpinaceae.
In late Roman and early Byzantine times the pure gold coin known as the solidus weighed 24 carat seeds (about 4.5 grams). As a result, the carat also became a measure of purity for gold. Thus 24 carat gold means 100% pure, 12 carat gold means the alloy contains 50% gold, etc.
Carob pods were the most important source of sugar before sugarcane and sugar beets became widely available. Nowadays, the seeds are processed for the use in cosmetics, curing tobacco, and making paper.