Harvesting is a crucial gameplay element in Merge Dragons!.
Most of the main merge chains can be harvested from some level for various products. In order to intiate a harvest, the player need to double-tap the wanted object or drag a dragon to that object. An ongoing harvest may be halted at any point before the completion of the harvest by tapping either the object being harvested or the dragon doing the harvesting.
Several objects can be harvested by more than one dragon at the same time. Depending on the max amount of possible dragons harvesting the object, tapping the object that max amount doubled, will result with the max amount of dragons harvesting the object. For example: a Stonehenge can be harvested by 2 dragons at max, therefore 4 quick taps on it will result in two dragons harvesting it.
Dragons Behavior During Harvest
Once an item has been harvested, one unit of stamina will be spent from the dragon's current stamina pool, and a miniaturised version of the item harvested from the object will appear over the dragon's head. If a dragon does not have enough stamina and is asked to harvest an object, a "Too Tired" message would appear above the dragon. If no dragons are available when tapping a harvestable object, a "No Dragons Available" message will appear above the object.
While carrying an item, a dragon's movement speed is halved. A dragon carrying a harvested item will attempt to drop the item near a group of similar items—so a dragon carrying a Furious Life Orb will attempt to drop it near either other Furious Life Orbs or other Life Orbs, and will only select a different destination if there is no space near the Life Orbs. If multiple groups of similar items are available, the dragon will choose a random destination among the available groups. Should there be no items available matching the harvested one, the dragon will drop the item in a random location (often near the object it was harvested from).
In case another item appears in the spot the dragon initially chose as the destination for its carried item, the dragon will hover for a second before selecting a new location to put down its carried item in. If the camp or level is currently at max capacity, the dragon will carry the item indefinitely until an open spot becomes available. If camp or level is full and the dragon holding an item is either dragged to a harvestable object, called by double tapping that object or tapping the dragon, the item it held will revert to a Loot Orb, which can then be tapped by the player once there is sufficient space in the camp or level. This trick may be used to stack up a large number of Loot Orbs of 1x1 sized items.
Dragons left idle may autonomously harvest objects. If the dragon in question has been directed by the player to harvest from a particular object, it will continually attempt to harvest from the same object (type + level) when possible while working autonomously (however, this does not include objects that are destroyed upon harvest, such as Necromancer Grass and Fruit). Should all objects of that type be inaccessible, or if the dragon has not before been directed to an object by the player, the dragon will pick a random, available object to harvest from. Note that exiting the camp or having a dragon run out of stamina will cause it to revert to this randomized behaviour.
Different objects have different harvesting times. Higher level objects will usually require more time to be harvested, though it is not always the case and can depend on the possible outcomes of the harvest. For example, Midas Trees will be harvested faster at higher levels, as the harvesting result is the same item (one Golden Apple). In contrast, higher Fruit Tree levels are increasingly slower to harvest, as they give progressively more valuable fruit.
Life Flowers deviate a bit in that the higher level of the two flowers which gives the same life orb will be harvested faster than the lower (e.g. a Glowing Life Flower and a Twin Life Flower can both be harvested for a Tiny Life Orb, but the Twin Life Flower will be harvested considerably faster than the Glowing Life Flower), but overall it still fits the rule that the higher level objects with better loot results result in a longer harvest time.
While most objects can be harvested at will, some objects have a harvesting cooldown—such as Mushrooms, Magic Mushrooms, Zen Temples, and Haunted Houses—and can only be harvested again once several minutes have passed. There is a known bug where exiting the camp and re-entering will reset the timer, efficiently negating the harvesting cooldown.