nancyanne, as far as I know, the carob is monoecious - it bears separate male and female flowers on the same plant. The dioecious plant bears either male-only flowers or female-only flowers. Myristica fragrans (nutmeg) is a dioecious plant and in the old days, planting the crop was like "Russian Roulette" - you found out what you had much too late. Nowadays, grafting techniques have taken much of the "trial and error" approach out of such undertakings.

The carob is a dioecious with only some trees being hermaphroditic

nancyanne, I understand that the tree bearing both male and female flowers but either one sex is suppressed or the sexes mature at differing times. I suppose that this means that the tree may not bear fruit. I have very little experience of the spp. but I found this article which might interest you.
American Journal of Botany © 1992 Botanical Society of America.

Abstract
The flowers of Ceratonia siliqua, an anomalous caesalpinioid legume in the tribe Cassieae, are unusual in being unisexual and in lacking petals. Inflorescence development, organogeny, and flower development are described for this species. All flowers are originally bisexual, but one sex is suppressed during late development of functionally male and female flowers. Ceratonia siliqua is highly plastic in sexuality of individuals, inflorescence branching pattern, racemose or cymose inflorescences, bracteole presence, terminal flower presence, organ number per whorl, missing floral organs, pollen grain form, and carpel cleft orientation. Order of initiation is: five sepals in helical order, then five stamens in helical order together with the carpel. Each stamen is initiated as two alternisepalous primordia that fuse to become a continuous antesepalous ridge; in some flowers, the last one or two stamens of the five may form as individual antesepalous mounds. Petal rudiments are occasional in mature flowers. Position of organs is atypical; the median sepal is on the adaxial side in Ceratonia, rather than abaxial as in most other caesalpinioids. This feature in Ceratonia may be viewed as a link to subfamily Mimosoideae, in which this character state is constant. .Want the full article?
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