Plant of the month: Carob tree

An excellent shade tree that thrives in full sun and is tolerant of alkaline and even salty soils, the carob tree has provided food for people and livestock since at least Biblical times. In hard times, it was sometimes the only food available for people and their animals.

However, this tree, which provides great, dense shade and edible seed pods, has some downsides, particularly for urban and suburban landscapes. The first is that, in addition to a deep taproot, it also has aggressive shallow roots. Secondly, it produces a lot of bean pods once it matures, which means a lot of litter if you don’t harvest them. Their trunks tend to produce a lot of suckers. Finally, some people complain of a musky “gym sock” smell from the pods during late fall when they are fresh and at their most numerous.

However, the tree, which comes from the legume family and originates from the Mediterranean region, has a lot going for it as well. Its leaves are dense and dark green, and have a lush appearance. The bark is an attractive grayish color and the trunks and main branches, if pruned correctly, can be quite sculptural. The tree grows up to 40 feet high and close to that in width, so while it takes up a fair amount of space it also provides a lot of shade. It is an excellent tree for our climate, and once established, will only require deep watering every three to four weeks.

These trees must be planted in full sun, and due to their final size will need lots of room. Make sure you plant them far away from any plumbing, hardscaping, or residential structures, due to the aggressive roots. For the first couple of years after planting, it will require deep watering once a week during hot weather and once every two weeks during the winter. In the second year, you can stretch out watering to every two weeks. They will require well-draining soil, as they hate to be wet constantly and must dry out between waterings. For this reason, they should not be mulched.

The trees are evergreen. They may suffer frost damage while younger, but older, established trees should be fine to about 20 F. They do well in poor soil and do not require amendments or fertilization. They have very deep taproots, and once established are not transplantable, but they may do relatively well in large containers as long as their other needs are met.

Some cultivars are male or female; if you don’t want the smelly pods you can look for a male cultivar; be aware, however, that the male trees also produce flowers, and that these are reported to smell like semen. Some cultivars are dioecious, which means they have both male and female flowers on the same tree. These will self-pollinate.

The bean pods are harvested when brown and dry. The hard seeds are removed and the pods can be ground into a powder. You can also grind the pods and seeds together into a flour. They contain a lot of sugar, and have a vaguely chocolate taste, so they can be used in cooking as a chocolate substitute. You can also eat the pods raw, and spit out the seeds. In addition, the pods can be processed into carob syrup, a sugar substitute.

The carob is thought to be the “locust tree” mentioned in the Bible and eaten by John the Baptist and the Prodigal Son. The carob does not contain any caffeine or related compounds, and is safe for animals including livestock, dogs and other mammals. Carob trees are also the source of locust bean gum, a frequently used thickening agent.

Historical reports suggest that carob seeds were used in ancient times to determine the weight (and thus the purity) of Roman gold coins. This was supposedly due to their uniform size, although modern analyses dispute this claim. Our word “carat” derives from the Greek word for carob, keration, or the Arabic qirat.