Carob trees (Ceratonia siliqua) are hardy in U.S. Department of Agriculture plant hardiness zones 9 to 11, where they commonly grow to a height of 35 feet but can grow as tall as 55 feet. They bloom in red in the spring; female trees, if pollinated by a nearby male tree, produce seed pods. You can collect the seeds in the summer or fall and pot them up right away for new carob trees. You can also buy carob seeds to plant in the spring or fall -- but you'll need to prepare these hard, dry seeds prior to planting.
1 Chip the hard seed coat on dried, hardened carob seeds with a sharp knife. Put the seeds in a large bowl, and fill the bowl with hot water. Leave the seeds in the water until they have swollen to three times their original size. This normally takes at least 24 hours.
2 Use flats or small containers 3 to 4 inches deep to pot up your fresh or prepared carob seeds. The containers must have holes in the bottom for excess water to drain out. Fill the flats or containers with 2 1/2 to 3 1/2 inches of vermiculite. Moisten the vermiculite with room-temperature water. Plant the seeds 2 to 3 inches apart and at a depth of 1 to 2 inches, or one to two times the width of the seed, in the moist vermiculite.
3 Set the planted containers or flats in bright but indirect sunlight where the room temperature is 70 degrees Fahrenheit or higher. Set a flat piece of hard plastic or plexiglass over the flats or containers to help retain moisture. Alternately, put individual containers in clear 1-gallon plastic bags and seal them. Check the vermiculite once or twice a week to make sure it remains moist. Spray it with room-temperature water from a spray bottle to moisten it, if necessary.
4 Take the plastic or glass off the containers or remove them from the plastic bags after the seeds germinate and the seedlings are visible. This usually takes about two months. Continue to keep the vermiculite moist.