University of Florida

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Tree establishment irrigation research at the University of Florida

Edward F. Gilman, Professor , Environmental Horticulture

What we know

  • Trees are irrigated up to 21 times each week in some nurseries.
  • Live oak trees (2.5" trunk diameter) watered regularly 2 to 3 times each week take about 12 months to establish their roots in the landscape. Bigger trees take longer.
  • For bare minimum survival, 2.5" diameter live oak planted in spring need water twice weekly for about 10 weeks, then no irrigation is needed provided normal rains begin.
  • You cannot make up for lack of frequency by applying large volumes of water infrequently.
  • Soil amendments in the backfill soil do not help reduce tree irrigation requirements.
  • It is better to apply irrigation frequently in the weeks and months immediately after planting trees then to apply the same volume over a longer period.
  • There is no data demonstrating that native trees or shrubs can get by with less water than non-natives after transplanting to the landscape.
  • Survival can be improved and water use reduced by using low volume irrigation technology.

What we do not know

  • Research-based irrigation requirements for trees other than live oak
  • Irrigation recommendations in extended drought; our studies were all done in more-or-less normal years.
  • Effect of plant size on irrigation requirements.
  • Effects of season on irrigation requirements.