Irrigation Management

 

Irrigation management after planting

(see irrigation table below for a starting point on newly planted trees)

Irrigation is imperative to a trees overall health and survival. 

Regular irrigation after planting encourages rapid root growth that is essential for tree establishment. Irrigation helps maintain and encourage the desirable dominant leader in the tree canopy on large-maturing trees. Instead of a dominant leader, trees that are underirrigated during the establishment period often develop undesirable, low, codominant stems and double leaders that can split from the tree later.

Splits (so-called frost cracks or sunscald) along the lower trunk have also been associated with under-irrigation after planting. Since most root growth occurs in the summer months, irrigation during this time is crucial. You could loose almost an entire year's root growth if you under-irrigate the first summer.

Unlike established plants, research clearly shows that recently transplanted trees and shrubs establish quickest with light, frequent irrigation. For trees planted in spring or summer, provide one (cooler hardiness zones) to three irrigations (warmer hardiness zones) each week during the first few months after planting. Daily irrigation in the warmest hardiness zones provides the quickest establishment.

Following the initial few months of frequent irrigation, provide weekly irrigation until plants are fully established. At each irrigation, apply 1 to 2 (cool climates) or 2 to 3 (warm climates) gallons of water per inch trunk diameter (e.g. 2 to 6 gallons for a 2-inch tree) over the root ball only (see the photo on bottom of page). We have found that more can be wasteful and that may not be necessary to apply irrigation to the soil around the root ball unless it was exceptionally dry.

In most landscapes that receive more than 30 inches of rain or irrigation annually, if the mulch area is maintained weed-free, irrigation does not need to be applied outside of the root ball. Never add irrigation if the root ball is saturated.

Once the tree is established you can water twice per month in warm weather in spring, summer, and fall and once or twice per month in winter in the first three to five years. Between years five and seven, water once every three weeks in warm weather and once every six weeks in winter. After this, the most trees should be able to survive on natural rainfall, However keep an eye on your investment.

New planting irrigation schedule starter:
Size of nursery stock
Irrigation schedule for vigor 1,3
Irrigation schedule for survival 2,3,4
< 2 inch caliper
Daily for 2 weeks; every other day for 2 months; weekly until established.
Twice weekly for 2-3 months
2-4 inch caliper
Daily for 1 month; every other day for 3 months; weekly until established.
Twice weekly for 3-4 months
> 4 inch caliper
Daily for 6 weeks; every other day for 5 months; weekly until established.
Twice weekly for 4-5 months

Notes on Irrigation: (click here for disclaimer on irrigation requirements)

1.) Delete daily irrigation when planting in winter or when planting in cool climates. Irrigation frequency can be reduced slightly (e.g. 2-3 times each week instead of every other day) when planting hardened-off, field-grown trees that were root-pruned during production. Establishment takes 3 (hardiness zones 10-11) to 4 (hardiness zones 8-9) to 8 (hardiness zones 6-8) to 12 (hardiness zones 2-5) months per inch trunk caliper. Never apply irrigation if the soil is saturated.

2.) Irrigation frequency can be reduced slightly (e.g. to once or twice each week) when planting hardened-off, field-grown trees that were root-pruned during production.

3.) At each irrigation, apply 1-2 gallons (cool climates) or 2-3 gallons (warmest climates) per inch trunk caliper to the root ball. Apply it in a manner so all water soaks into the root ball. Do not water if root ball is wet/saturated on the irrigation day.

4.) Trees take much longer to establish than regularly irrigated trees. Irrigate in drought the following summer.

Design irrigation so water lands on the root ballDesign irrigation so water lands on the root ball

All roots on transplanted trees are located in the root ball so a system designed to deliver water there is most efficient. In the photo (right), poly irrigation lines were spiraled around the top of the ball so water is delivered to all the roots.

"Illustrations, PowerPoints or photos by Edward F. Gilman, Professor, Environmental Horticulture Department, IFAS, University of Florida."

 

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