Seeing a plastic bag around a tree trunk may seem a strange sight, but there is actually a very good reason for this unusual setup. A plastic bag around a trunk is most likely a tree-watering bag.
Tree-watering bags provide newly planted trees with the appropriate amount of water needed for optimal growth without requiring homeowners to continually water the tree. These bags slowly release water to the root zone of a tree through drip holes in the bottom.
Newly planted and young trees less than 2 years old need about 15 gallons of water on a weekly basis throughout the growing season. Providing enough water without significant runoff proves difficult. These bags deliver just the right amount of water in several hours without requiring too much time or effort on the part of the homeowner. Different sized bags exist for use with trees with various moisture needs.
Plastic tree watering bags are available for purchase from companies or at your local garden center. Some homeowners create their own watering bags by hanging a 5-gallon bucket above the root ball of the tree. Punching about a dozen holes in the bottom of the bucket ensures a slow and steady water delivery system in measured amounts.