A reef will spawn a Heart of the Town. Each reef has 3 possible locations where they will spawn a Heart of a Town; each time a Heart spawns, a random location is chosen. The heart of the town can be picked up by right clicking them, while they are planted to the reef.
Alternatively, if a heart of the town is not harvested by a player after 10 minutes, it will pop off as an item, which can be picked up by players or hoppers. The heart of the town item will despawn after about 10 seconds if it is not picked up.
Once a heart of the town is harvested or naturally sheds, the reef will spawn a new heart of the town 10 minutes later.