Almost all the trees we plant are watered by the Department of Public Works for three years after they are planted, using the green, slow-draining water bags we provide. The frequency of watering depends on the district, and is often every few weeks. You may not notice the bags being filled, as crews may come in the early morning - just know if the tree is alive, it’s being watered!

If you are concerned that multiple blocks in a district have young trees that seem to lack water, please contact San Francisco Public Works Bureau of Urban Forestry at urbanforestry@sfdpw.org.

Please send them the following information:

• Address of the tree(s), OR the name and the street and the closest cross streets.

• Photos of the trees that need attention

Our young trees are installed with a green 15 gallon water bag attached to one of the wooden support stakes. There is an opening at the top of the watering bag near the handles where a hose is inserted to fill the bag. The water should drain slowly out of the bag over a few hours through 2-3 tiny holes at the bottom of the bag near the seam. These fast-filling, slow-draining bags are useful for young trees’ root establishment, reducing soil erosion, preventing over-watering, and watering crew efficiency.

Here’s a how-to video for instruction on how to use a water bag.

Bag not draining? You can easily poke a few more small holes near the bottom of the bag with a push pin or a safety pin. It helps to do this when the bag is full, and to not make the holes too big so that the water can drain slowly, like a drip irrigation system.

Bag draining too fast? If the holes are too large, you can tape them using duct tape. Just make sure the bag is dry before applying the tape. Also, some holes can be plugged effectively with tanbark or sticks.

Need a replacement bag? The quickest option is to visit a local garden or hardware stores; many have water bags (or ‘gator’ bags) available for purchase. Find a video about how to install them here. 

If this is not an option that makes sense for your situation, we invite you to request a bag through our Tree Care Request Form and send us some photos. We will install a used, functioning water bag when we are next in your neighborhood (wait time- within a few weeks).

The standard recommendation for young trees is to water 15-20 gal per week, which would mean filling a water bag once per week until it's about 3 years old.

Sandy soils, hot weather, infrequent rainfall, and strong winds that can be common here in the City are all reasons that a young tree would benefit from more water. Even in the rainy months, the 3x3ft basins will get approximately 5 gallons of water per 1 inch of rain, which often does not add up to the recommended 15 gallons a week. Adding extra water to the watering bag or directly to the soil once a week is a great way to help the tree establish a deep and stable root system.

Just be sure that enough water is applied at a time so that the soil is moist a few inches below the ground (deep watering = deep roots), and that the soil has time to dry before you water again (watery swamp = root rot diseases).

After trees are in the ground for 3 years, weekly watering is generally no longer needed, and the water bag may no longer be as effective. Trees at this stage can benefit from a periodic deep soak (which you can do with a hose or a bucket a few times a year), so that water continues to reach far down into the root system, which at maturity is often between 1 to 2 ft below the ground.