Harvest Moon is an Item that can be found within common locations, including choice enemy Camps, given by Spouses, and rarely as a reward from Seasonal Festivals. Upon being picked up, all Crops will grow faster at night. The effect can be seen in action through the small particle affects that will appear. As soon as the next dawn arrives the effects of Harvest Moon will not be felt again until the next night, at which point it will reappear and boost Crops again.
Several other Items are capable of boosting Crop growth, including Growth Aura, Turret Growth Aura, Bees, Hummingbirds, and Rain Scrolls. With the exception of Rain Scrolls, Harvest Moon is the only one that simultaneously affects all Crops planted on the Farm at once. This alone can give this Item innate value in that regard. In addition, since Corpse-a-Copia's fight takes place entirely at night Harvest Moon will permanently be in effect for the entire duration of the battle. However, Harvest Moon offers no benefit during the day, making other Items better for that situation.