Establishment period for trees

When a tree is established, many roots will have grown a distance equal to approximately 3 times the distance from the trunk to the branch tips (Gilman 1988; Watson and Himelick 1982). During the establishment period, shoots and trunk grow slower than they did before transplanting. When their growth rates become more or less consistent from one year to the next, the tree is considered established.

In moist climates, by the end of the establishment period a tree has regenerated enough roots to keep it alive without supplemental irrigation in a landscape where roots can expand uninhibited by urban structures. In the drier parts of central and western US, the turf and landscape irrigation system may have to supplement rainfall to provide enough water for survival after establishment. Trees in unirrigated landscapes in dry climates may need supplemental irrigation beyond the end of the establishment period. This is especially important if the trees are not adapted to the dry climates.

Trees provided with regular irrigation through the first growing season after transplanting require approximately 3 months (hardiness zones 9-11), 6 months (hardiness zones 7-8), or one year or more (hardiness zones 2-6) per inch of trunk diameter to fully establish roots in the landscape soil. Trees in desert climates may take longer to establish. Trees that are underirrigated during this establishment period are likely to require additional time to establish because roots grow more slowly. Most trees are underirrigated during the establishment period. Because roots are not fully established, be prepared to irrigate through the entire establishment period, especially in drought. Since most root growth occurs in summer, be sure soil moisture is appropriate during this crucial season.

Table 1. Establishment rate is influenced by a variety of factors.

These guidelines are based on the following research: Beeson and Gilman 1992; Gilman 1994; Gilman and Beeson 1996; Gilman al. 1996; Gilman et al. 2001; Gilman et al. 2002; Harris and Gilman 1993; Watson and Himelick 1982.