Ceratonia siliqua

The carob (Ceratonia siliqua) is a flowering evergreen tree or shrub in the legume family, Fabaceae. It is widely cultivated for its edible pods, and as an ornamental tree in gardens and landscapes. The carob tree is native to the Mediterranean region and the Middle East. The ripe, dried, and sometimes toasted pod is often ground into carob powder, which is sometimes used to replace cocoa powder. Carob bars, an alternative to chocolate bars, as well as carob treats, are often available in health food stores. Carob pods are naturally sweet, not bitter, and contain no theobromine or caffeine. The carat, a unit of mass for gemstones, and a measurement of purity for gold, takes its name from the Greek word for a carob seed, keration, via the Arabic word, qīrāṭ. The word 'carob' comes from Middle French carobe (modern French caroube), which borrowed it from Arabic خَرُّوبٌ (kharrūb, 'locust bean pod'), ultimately perhaps from Akkadian language kharubu or Aramaic kharubha, related to Hebrew harubh. Ceratonia siliqua, the scientific name of the carob tree, derives from the Greek kerátiοn κεράτιον 'fruit of the carob (from keras κέρας 'horn'), and Latin siliqua 'pod, carob'. In English, it is also known as 'St John's bread', as well as 'locust tree', (not African locust bean) the designation also applied to several other trees from the same family. The unit 'carat', used for weighing precious metal and stones, also comes from κεράτιον, as alluding to an ancient practice of weighing gold and gemstones against the seeds of the carob tree by people in the Middle East. The system was eventually standardized, and one carat was fixed at 0.2 gram. In late Roman 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. The carob tree grows up to 15 m (49 ft) tall. The crown is broad and semispherical, supported by a thick trunk with rough brown bark and sturdy branches. Its leaves are 10 to 20 cm (3.9 to 7.9 in) long, alternate, pinnate, and may or may not have a terminal leaflet. It is frost-tolerant to roughly 20 °F (−7 °C).