Newly planted trees must be watered regularly for the first two to three years. During the summer dry season (roughly May to October), deep-root watering is recommended. Begin with 15 gallons of water per tree per week, and adjust as needed. During the remaining months of the year, monitor the root zone for dryness and water as needed. Good watering practices will promote vigorous growth, ensure well-formed root development, and help produce a beautiful tree for years to come.
How to water your tree for establishment:
- Newly planted trees generally need about 10 to 30 gallons of water each week in dry conditions. Healthy, mature trees generally don’t need to be watered. Watering during rainy winter months is not necessary.
- Watering slowly will help penetrate the soil deeper. Watering can be done with a hose for several minutes a week. Watering tubes and 5-gallon buckets with holes in the bottom that are placed next to the tree trunk are other ways to deliver water to your tree.
- Although it is possible to over water a new tree, it is difficult to do in a dry Portland summer. When in doubt, water.
- If water starts to run off the surface, water at a slower rate, water on the other side of the tree, or loosen up any hard surface on the soil so the water can percolate into the ground.
- Watering a tree deeply about once a week is generally better than providing a shallow watering more often. Deep watering encourages roots to grow deeper, and deeper roots do not dry out as quickly as surface roots.
- It can take up to five years for a newly planted tree to establish itself in its new environment. Watering once a month or so for 2-3 years after the first 2-3 years is recommended for optimal tree health. Good watering practices during the establishment period are important to the tree’s survival.
- When watering, take advantage of the looser wet soil and remove any weeds or grass from around the tree. Mulch can also be added, but remember to keep the mulch from touching the base of the tree.
Maintaining a layer of mulch around newly planted trees has many benefits. Mulch will help to control the growth of grass and weeds that compete with your tree for resources. Mulch will also help the tree to retain moisture, regulate temperature extremes, and as the mulch breaks down, it adds nutrients to the soil.
How to mulch your tree for establishment:
- Remove grass and weeds in a 3-foot circle around the base of the tree. Take care not to damage your tree's roots when removing grass and weeds.
- Choose a mulch made from organic material such as wood chips or bark chips. Inorganic materials such as stones and rocks are not recommended as they may get hot and do not improve the soil over time.
- Stay 3 inches away from the trunk of the tree. Do not allow the mulch to be in contact with the base or trunk of the tree.
- Apply a 2 to 4-inch layer of mulch in a 3-foot circle around the tree. If the mulch layer is too thick, it can reduce air circulation to the roots.
- Reapply mulch each year, or as needed to maintain a 2 to 4-inch layer surrounding the tree.
After two or three years, the tree should be pruned to remove poorly connected branches and to train the tree for street and sidewalk clearances. In most cases, achieving street and sidewalk clearances may not be possible for several years. Click here for information on proper pruning and how to obtain a free street tree pruning permit.
Trees should not require fertilizer, but if a tree appears unhealthy, check with a certified arborist to determine if fertilizer or some other care is needed and how fertilizer should be applied.
It is a good idea to regularly monitor your trees for:
- Watering needs
- Mulching needs
- Insects or disease
- Bark damage
Proactive monitoring can catch adverse conditions before they threaten the health of the tree. Familiarize yourself with the typical conditions of your tree so you will notice when any changes appear in the tree or its immediate surroundings.
The Portland Bureau of Transportation (PBOT) composts more than 5,000 tons of leaves collected through the city's Leaf Day program each year. Removing leaves from our streets is critical to keeping streets safe from clogged storm drains, flooded intersections, and slippery streets.