Drip Irrigation Systems for Trees

Equipment

• Drip system equipment includes a back flow preventer, pressure reducing valve, irrigation valves and controller. With home drip irrigation systems, polyethylene tubing is an acceptable and less expensive alternative to using PVC pipe.

Separate Valves

• Ideally, the irrigation system should be set up so that trees are on a separate valve and water schedule than shrubs and ground cover. This is because trees need a longer water delivery time, and if they are on the same system as smaller plants, either the shrubs are overwatered or the trees are underwatered.

Emitter Placement and Quantity

• Emitters for trees need to be spaced equally around the canopy. The quantity of emitters, and the total number of gallons per hour delivered, is based on the size of the tree. For example, a newly planted 5- or 15-gallon tree would need three 2-gallon-per-hour emitters. A tree with a canopy of 10 to 14 feet diameter needs 12 2-gallon-per-hour emitters.

  When emitters are placed on a newly planted tree, they should be situated to they provide water to the root ball. As the tree grows, however, they should be moved out away from the trunk so they are matching the extent of the canopy. You should also be adding one new emitter for every 2 or 3 feet additional canopy diameter.

  If your tree is on a slope, all of the emitters should be placed on the uphill side in a half moon configuration. Since water flows with gravity, the flow from the emitters will run downhill, eliminating the need for emitters on the downhill side of the plant.

Watering Times

• The irrigation schedule for trees is based on the size of the tree and the time of year. The efficiency of drip irrigation is dramatically reduced if you are watering your trees the same amount all year long. Irrigation should be set for once a week during the hot, dry part of the summer. From November through March twice a month is sufficient. The exception is newly planted trees, which should be watered every day for a week, every other day during the second week, every third day during the third week, and once a week for the remainder of the first year.