Flora and Fauna News

An Evening Scent:
Carob Trees in Flower

By Michael Plagens
Sonoran Desert Sciences

PHOENIX, Az. ----- With the arrival of chilly autumn nights the Carob Tree begins its blooming period. The flowers release a strong, peculiarly scented perfume into the night-time air, and with cool air forming at the ground surface after dusk, the odor lingers close to the ground. It is detectable hundreds of meters from the originating tree.

The Carob Tree is a popular shade tree grown in metropolitan Phoenix as well as parts of California. It's original home is the Mediterranean where it has been widely cultivated in Turkey, Spain, Tunisia and Israel for at least 4,000 years. The scientific name of the carob tree, Ceratonia siliqua L., derives from the Greek keras, meaning horn, and the Latin siliqua for the bean pod fruit.

Carob is a trioecious tree, with male, female and hermaphroditic inflorescences usually on different trees. The small flowers occur in spikes with 40 to 70 flowers, that together are called an inflorescence. There are no petals, but the anthers are large and bright yellow with pollen on the males. Curiously the flower spikes are borne directly from old growth twigs and branches.

Being a member of the Legume family, the female carob flowers produce bean pods. The fruit of the pod itself is the source of the cocoa substitute while the bean yields Locust Bean Gum, which is used as a food additive.

Research is supporting the idea that carob flowers are Bat Pollinated. This seems reasonable given that the perfume is released at night and during the cool season when warm-blooded pollinators have an advantage over insects. The The Egyptian Fruit Bat, Roussettus aegyptiacus, native to the Mediterranean region consumes the fruit and may be an important pollinator as well. Some pollination may occur by the wind, although this seems to be rather ineffective for high rate pollination.

Compound leaf of the Carob Tree is even-pinate.
(Click to Enlarge)
Photo by Michael Plagens

Spike of male Carob Tree flowers.
(Click to Enlarge)
Photo by Michael Plagens