Care of Recently Planted Trees

Watering

Regular irrigation after planting encourages root development for tree establishment. Under-irrigation often leads to slow establishment, canopy dieback, and bark splits (frost cracks and sunscald) on the trunk. Recently planted trees and shrubs can establish quickly with light, frequent irrigation applied directly to the root ball.

Refer to Table 1 for frequency and the volume of irrigation based on the size of tree planted. This information has been taken from the University of Minnesota publication, Watering Newly Planted Trees and Shrubs, by Kathy Zuzek. Table 2 provides more detailed information based on the size of the tree planted and irrigation requirements.

Table 1. Irrigation and establishment time of newly planted trees based on caliper size.

Caliper size (measured 6 inches above the top of the root ball)	Gallons of water to apply at each irrigation	Root establishment time
One Inch	1 to 1.5 gallons	1 to 1.5 years
Two Inches	2 to 3 gallons	2 to 3 years
Three Inches	3 to 4.5 gallons	3 to 4.5 years
Four Inches	4 to 6 gallons	4 to 6 years
Five Inches	5 to 7.5 gallons	5 to 7.5 years
Six Inches	6 to 9 gallons	6 to 9 years

Frequency of irrigation should be applied as follows:

• 1-2 weeks after planting, water daily.
• 3-12 weeks after planting, water every 2 to 3 days.
• After 12 weeks, water weekly until roots are established.

Larger volumes of water applied infrequently may result in drought-stressed roots. Soil amendments added at planting do not reduce the need for frequent irrigation. Drought-tolerant and native species are not drought-tolerant until the root system becomes established – watering recommendations from Table 1 should be followed. In sites without ideal irrigation management, smaller-sized nursery stock and waterwise and native species should be considered.

When watering newly planted trees, check the soil frequently and water according to need. The soil could be dry in the root ball and wet in the backfill, or wet in the root ball and dry in the backfill. Monitor irrigation if the tree is planted in a newly sodded/seeded irrigated lawn.

Table 2. Estimated irrigation needs of newly planted trees and shrubs during the growing season.

Size of Nursery Stock	Irrigation Need for Vigor
<2-inch caliper	Daily for two weeks Every 2-3 days for two months Weekly until established
2-4-inch caliper	Daily for four weeks Every 2-3 days for three months Weekly until established
4-inch caliper	Daily for six weeks Every other day for 5 months Weekly until established

Check if water is needed prior to irrigating; a common mistake on compacted and clayey soils (with poor drainage) is to apply too much water per irrigation, waterlogging the planting hole. Never apply irrigation if soil is saturated. In Colorado’s dry, semi-arid climate, there is benefit from applying additional irrigation outside the root-ball area to maintain soil moisture in the rooting area.

Fall and Winter Watering

In Colorado winters without routine moisture, water newly planted trees monthly on sunny days when it is above 40 degrees Fahrenheit and the ground is not frozen. Water early in the day, if possible, to allow water to soak into the ground before it freezes at night. Refer to CSU Extension resource Fall and Winter Watering for additional information.

Mulch

Apply mulch around newly planted trees to protect them from lawnmowers, string trimmers, and grass competition. Wood or bark chip mulch is highly recommended on newly planted trees. Trees with a mulch ring typically have 20% increased growth compared to trees where grass grows up to the trunk, which competes with the tree for resources.

In a landscape setting, the mulch ring is a minimum of two to four feet wide but can be up to the width of the dripline (spread of branches). Apply wood chip mulch at a depth of 4-5 inches thick, which provides better weed control, soil moisture retention, and helps prevent soil compaction.

On newly planted trees, do not place mulch on top of the root ball. On established trees, keep mulch at least six inches away from the trunk. Never pile wood/bark chips up against the trunk. For those in fire-prone areas, do not use organic mulch near homes or structures. Refer to CSU resource Firewise Plant Materials for more information.

Fertilization

During the establishment phase, fertilization needs for newly planted trees are very minimal. Providing high-nitrogen fertilizer may encourage canopy growth at the expense of root growth. In situations where soil fertility is low, but water and other growth factors are not limiting, a half-rate fertilizer application with a time-release product may be acceptable.

Never fertilize trees in the establishment phase that are showing signs of stress. When an unestablished tree is under stress, fertilizers can push new growth that a stressed tree cannot support. Woody plants do not respond to “starter fertilizers” like herbaceous plants.

Pruning

Pruning should be limited to the removal of dead and broken branches and minimal pruning to maintain a single leader or to correct for poor branching structure. When purchasing trees, select trees with good structure that will not require immediate pruning.

Structural training for the tree continues in the growth phase (after the roots have established and the canopy shows significant annual growth).

In situations where trees will not receive any structural training while young, it may be desirable to correct structural major defects as part of the planting process. This is primarily removal of codominant trunks and spacing of secondary trunks. However, major pruning at planting may slow root establishment.

This publication, reference GardenNotes #635, is developed as part of the Colorado State University Extension Master Gardener Program.