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Tree Care

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A Guide for Watering Trees

Trees are an important part of every community and provide many benefits. Watering properly and efficiently is essential to the health and preservation of our City’s beautiful trees.

Deciduous Trees

Deciduous trees typically lose their leaves seasonally, usually during the autumn months. They have flat, broad leaves, used to catch light. Deciduous trees can be found in most regions of the world. A few deciduous trees commonly found in Hillsboro are: Bigleaf Maple, Black Cottonwood, Oregon Ash, Pacific Dogwood, and Willow.

 A leafy deciduous tree

Coniferous Trees

Coniferous trees typically grow cones, and have leaves that are either long, pointed needles or are small, flat scales. Most coniferous trees are also evergreens, but it is important to note that not all coniferous trees are evergreens. Coniferous trees common to this area are Douglas Fir, White Fir, Sugar Pine, Ponderosa Pine and Cedar. These trees prefer well-drained soils, with high sand content.

 A coniferous pine tree stands tall in a forest

Fruit Trees

Fruit trees are similar to deciduous trees in that they lose their leaves seasonally. The difference is that fruit grows seasonally, ranging from late spring to early winter. Some fruit trees around Hillsboro are Apple, Cherry, Fig, Plum, and Pear. Most are tolerant of poorly drained soil and prefer full sun.

 Two apples grow on a branch

Watering Trees

How Much to Water

As a general rule of thumb, for every one inch of trunk caliper (tree diameter), your tree needs 5–10 gallons of water; how often will depend on the maturity of the tree. 

How Often to Water

In drought, don’t stop watering altogether.

Young Trees (1–3 years) generally require about 5–7 gallons per week for every one inch of trunk caliper. 

Mature Trees require 8–10 gallons about every two weeks for every one inch of trunk caliper. 

How to Water

There are several different ways to water your trees.

  • Open the hose slightly with a timer on the spigot
  • Use a soaker hose around the canopy line of the tree (insert pic)
  • Water with a drip irrigation system
  • Use a 5 gallon bucket with small holes drilled into it
  • Use a small sprinkler on hose with timer on a spigot
  • Use tree bags
 A soaker hose is placed on the ground in a circle around the roots of a tree

Where to Water 

To encourage outward root growth, water deeply and at the edge of the canopy, rather than right next to the trunk. 

Symptoms of Drought 

  • Wilting or browning leaves on deciduous trees
  • Deciduous trees dropping leaves prematurely
  • Short flowering time on fruit trees
  • Fruit dropping prematurely from fruit trees
  • Conifer needles changing to yellow, red or purple

Symptoms of Overwatering 

  • Yellow leaves, usually starting on the lower branches, at the inside of the canopy
  • Wilting of young shoots
  • Brittle, green leaves
  • Black or dark brown roots (root rot)
  • Fungus or algae growing on the soil surface roots

Soil and Mulching

Benefits of Mulching

Mulching reduces soil moisture loss, insulates soil which protects roots from extreme temperatures, and improves soil fertility as the mulch decomposes. 

By correctly using mulch, building a water basin around the tree trunk, and watering slowly in multiple cycles, your trees will thrive and you could save water and money. 

 Mulch surrounds a tree trunk
Slope and Soil Moisture

When watering in steep slope areas, it is crucial to apply water slowly to prevent water from running off and to insure that water reaches the trees roots

If possible, check soil moisture using a probe to 16–18 inches.

Soil Types

Determining what texture of soil you have is crucial to knowing how well it will absorb water and which watering technique is best suited for your trees.

  • Clay Soils hold water well and cause water to spread out horizontally  
  • Loam Soils contain a high amount of broken down, organic matter
  • Sandy Soils are less likely to cause runoff and water tends to run straight down
 Three different soil types vary in color and texture

When in Doubt, Call an Arborist

Arborists are professionals trained in the art of science of planting and maintaining trees. They are trained to provide proper care. If you have any questions or concerns regarding the health and safety of your trees, call a local arborist for recommendations.