Watering your tree is essential to its health and survival for the first few years after it’s been planted. Watering slowly and deeply is better for your tree’s over-all health then fast and frequent waterings. Watering before 10 a.m. and after 8 p.m. can reduce the amount of water lost to evaporation.
The amount of water needed will vary by tree species and soil type. Here are general guidelines.
Sandy Soil
Using the bucket method to water a newly-planted tree on Potrero Hill, June 2009.
The sandy soils in the Western half of the city generally require more frequent watering, because they drain faster than clay soils. If you live in an area with sandy soils, water two or three times a week, 20-30 gallons total during the first two years after planting, followed by half as much for the 3rd year.
Water runs through sandy soil quickly, travels straight down and does not spread to the side. Therefore, it’s best to move your water source around in order to reach all of the roots.
When sand dries out too much, it can actually become hydrophobic: it refuses to accept water. If this happens, add a watering agent such as Water-In to enhance soil penetration. Water-In is available at most garden stores. Do not use detergent as a substitute, as this will be toxic to the plant.
Clay Soil
Heavy clay soils drain slowly. If the water hasn’t drained into the soil 10 minutes after you have finished watering, you have a heavy clay soil. Apply less water less frequently.
Water 10-15 gallons per week with a slow drip. The heavier the soil, the less water it may need. Watch to see how fast the water drains and avoid creating a swampy condition. Roots need oxygen as well as water. Try not to step on or dig in the soil when it is wet, because you can squeeze the oxygen out of it. If clay soil dries out too much, water may just puddle on the surface. Try to keep the soil evenly moist without flooding it.
This is not a strict formula. If your tree-watering schedule is not working for your tree health or soil type, adjust as necessary.
There are three main methods for watering:
The Bucket Method
The bucket your tree came in holds about 10 gallons of water. You can use it to water your tree. Line it with a trash bag and fill it with water. Poke a small hole in the bottom of the bag at one of the bucket drain holes. Let the water drain out slowly near the trunk, but not on it. Fill it two times once a week every week, even when it’s raining (San Francisco’s average annual rainfall is only about 20 inches, and 1” of rain = about 5 gallons of water per tree).
The Watering Bag Method
This method is the same as the Bucket Method only using a gardening product rather than reusing the bucket from planting. The watering bags usually hold around 20 gallons of water so would only need to be filled one time per week. Be sure to install the watering bag zipped around one of the support posts for the tree rather than the tree itself. We also recommend installing it on the uphill post so that as the water drains from the bag it will run toward the tree. Installing it on the base of the tree may cause crown rot due to the moisture that collects at the base of the tree. In areas with heavy foot-traffic it may be prudent to run a zip-tie through the hoops on the bag and around the post in order to deter theft.
You may purchase Treegator® watering bags from us for $25 each at the time your tree is planted, or you can order them online anytime.
Yes, you should water a young tree even during rainy season (1981, Mission neighborhood).
Garden Hose Method
Run your hose on a slow trickle for 1.5 to 2 hours once a week into the tree basin, even when it’s raining.
If you have a watering tube, alternate watering between the soil surface and through the tube for the first year. Water only through the tube during the second and third year. Note: sandy soil areas do not need watering tubes.
If you need help with watering schedules or to determine your soil type, contact nina, our tree care coordinator, by phone at 415-525-8387 or by email with our contact form.