Common Name(s): Carob, St. John’s Bread, Locust Bread

Synonym(s):

Family: Fabaceae

Native To: Mediterranean region and west Asia.

Native Habitat: Arid regions.

Growth Habit: Rounded tree that can reach 30-40 feet tall and wide.

Flowering: September to November

Distinguishing Characteristics: The numerous branches of the tree make the canopy quite dense. The leaves which are alternately arranged and pinnately compound, are 4 to 10 inches long and hold 8 to 10 leaflets, each about 2 inches long. The leaves are dark green and thick. The flowers are unlike any other in the Legume family. They are very small, inconspicuous, and unisexual (either male or female). About 11 months pass from flowering to fruit ripening. The bean pods are green during development and then turn dark brown when ripe. The beans can become quite large, ranging from 4 to 10 inches, and can hold 5 to 15 seeds, which resemble a grains of corn in shape.

Natural History and Cultivation Notes: The genus name comes from the fact that the seeds were once used as a standard measure of weight or carat. In the Bible, it is referred to as a shade tree in Israel, a place where even today it is still wide spread. The Greeks introduced the tree to the Mediterranean, where it has remained a highly valued crop. This tree is also commonly known as St. Johns Bread, because John the Baptist is said to have sustained himself on Carob beans while traveling in the wilderness.

Carob trees were first introduced to of southern California and Arizona in the mid 1800s. Variety trials in southern California measured sugar content, bean weight, response to climate and irrigation regimes, and ripening time. These tests identified several promising clones for the hotter regions (among them 'Casuda' from Spain, 'Sfax' from Tunisia, and 'Tylliria' from Cyprus). Presumably they might also have been tested in some of the early UA Cooperative Extension efforts as well.

The oldest existing UA trees are located on the western side of campus at the Fish Pond, near Park Avenue. Chuck Raetzman, former Grounds Director, remembers planting them as 15 gallon plants around 1970. The first winter they froze, but resprouted in the multiple trunks that support them today. These trees have crown diameters of over 30 feet, and give welcome deep shade. Another cluster of younger trees were planted by Warren Jones near the Visitor Center on the main Mall - but they have had to be moved. We call these the "Khadafy Carobs" - because of the following tale: Warren and other Tucson experts were asked by the Khadafy government to visit Libya in the mid 1980s, to assist in developing a public park which would be similar to the Arizona Sonora Desert Museum. When the group toured the site, there were many carob trees growing in a situation that seemed similar to the southern Arizona conditions. Warren asked permission to collect seeds, and they were germinated here at the University’s Campbell Agriculture Center. These were just getting to be full grown when the new Meinel Optical Sciences expansion was under construction. Fortunately, the Campus Arboretum was able to advocate for transplanting them to another site, north of the Tennis Courts, just east of Campbell on 2nd St.

In milder areas of California, carob may be escaping into disturbed washes and some cultivated areas. Although the species is a slow grower, if conditions are right, the deep-rooted seedlings do need to be controlled. Reports from the UC Davis and Nature Conservancy indicate that if seedlings are not actually pulled out, they resprout from the cut end. We are not aware of any serious escaping in Tucson near to the University of Arizona, but we will be vigilant!

Reports on cultural needs show why Ceratonia siliqua can thrive in the low deserts of the southwestern US. In Israel, trees will prosper in temperatures over 112 F, if provided with supplemental irrigation. Soil that is neutral or alkaline is best. Several sources mention that they do not like wet feet - will not take shallow frequent lawn irrigation. (One of the best looking trees on the UA campus does get flooded with overflow from the Fish Pond cleaning/aerating activities, and the deep soaking does not seem to have resulted in any ill effects.) However, like many other Mediterranean natives, their requirements for winter watering are key - they need winter rains more than they need excessive summertime irrigation.

Ethnobotany: The main use and economical importance of this tree is as a cocoa substitute. The walls of the pod and the partitions in the fruit contain very high concentrations of sugar, more minerals and vitamins, and less carbohydrates and fat than cocoa. The bean pulp is also mixed with other feed to obtain a high quality, nutritious, and superb tasting fodder for horses, cattle, and goats. Another major use of this species is for the production of gum, taken from the seeds after shuttering and separation, and used in many commercial food products as a thickening agent.

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