A tree watering bag is a vinyl reservoir designed to wrap around the trunk of a newly planted tree. The bag holds a significant volume of water, often between 15 and 20 gallons, which is then delivered directly to the root zone. These devices have become a common tool for homeowners and municipalities seeking to simplify the demanding irrigation schedule required for establishing young trees.
The Mechanics of Slow-Release Watering
The function of a tree watering bag is to deliver a controlled, prolonged supply of water to the soil surrounding the tree’s root ball. This is achieved through a gravity-fed system that utilizes small perforations or drip points located at the base of the bag. Once the bag is filled with water, hydrostatic pressure forces the water out slowly.
The design ensures that a substantial volume of water is released over an extended period, typically lasting five to nine hours per fill. This extended delivery window allows the water to infiltrate the soil deeply, directly targeting the area where the newly forming roots need hydration. The controlled release also minimizes loss from evaporation, which can be substantial when watering with a conventional hose or sprinkler.
Effectiveness for Newly Planted Trees
Tree watering bags are particularly beneficial during the first one to two growing seasons, which are the most challenging period for a transplanted tree. Newly installed trees lose up to 95% of their root structure during the transplanting process, which leaves them vulnerable to dehydration and stress. The bags provide a consistent and reliable source of moisture that directly supports the root establishment phase.
Providing a steady water supply directly to the root zone helps mitigate the effects of transplant shock, which is the decline in health following relocation. The sustained saturation encourages the tree to develop a deeper, more resilient root system rather than shallow roots that seek surface moisture. Using the bags reduces the frequency of manual watering, often requiring a refill only once every five to seven days for most new plantings.
Common Drawbacks and Usage Errors
Despite their advantages for new plantings, tree watering bags have limitations, especially when used incorrectly or for too long. Prolonged use beyond the first few seasons can encourage the tree to rely on the constant, localized moisture, which may lead to the development of shallow roots. These roots can be easily damaged or stressed once the bag is removed, defeating the purpose of promoting deep growth. Arborists generally recommend removing the bags after one or two growing seasons.
Another potential issue arises from the bag resting against the trunk, which can create a constantly dark and moist environment around the bark. This condition can promote the growth of mold, mildew, or fungal diseases, and may also attract pests. Additionally, if the bag is not positioned correctly, its weight when full can cause abrasions or damage to the young, delicate bark, particularly if it rubs against the trunk.
Proper Installation and Maintenance
The bag should be placed around the trunk and zipped up, similar to a jacket, with the zipper closure running vertically. For trees with larger diameters, typically over three inches, two bags can be zipped together to completely encircle the base.
Installation Procedure
When filling the bag, a hose should be inserted into the fill opening, and the bag should initially be filled to about one-quarter capacity. The user should gently lift the bag by the straps located at the top to fully expand the bottom gussets where the drip holes are located. This ensures the water flows properly and evenly. The bag should then be filled completely, and the fill opening should be covered to keep debris out.
Maintenance
Users should periodically check the drip holes for clogs. Using only clean water is recommended to prevent the irrigation openings from becoming blocked.