Drip irrigation is an efficient method for delivering water directly to the root zones of trees, minimizing the water waste common with conventional sprinklers. This targeted approach conserves water by reducing loss from evaporation and wind drift, which is beneficial for large plants with deep root systems. Installing a dedicated drip system ensures trees receive the deep, infrequent watering they require to develop strong, healthy roots, rather than the shallow, frequent watering that promotes surface roots. This guide provides a practical, step-by-step process for setting up a system designed to meet the unique hydration needs of both young and mature trees.
Gathering the Essential Materials
The foundation of a reliable tree irrigation system begins with selecting the components necessary for high-volume delivery. Mainline tubing, typically a half-inch or three-quarter-inch polyethylene pipe, carries water from the source to the trees. Since trees require a greater volume of water over a wide area, the system uses multiple emitters or specialized drip rings for coverage.
Quarter-inch micro-tubing connects the mainline to the individual emission devices. Emitters are typically pressure-compensating (PC), ensuring a uniform flow rate, such as one or two gallons per hour (GPH), regardless of elevation changes or distance from the water source. Connectors like tees, elbows, and couplings are needed to route the mainline tubing and make connections. A system punch is also necessary to create clean holes in the mainline for inserting the micro-tubing couplings.
Installing the Head Assembly
The head assembly manages the pressure and cleanliness of the water entering the drip lines and connects directly to the water source. The installation sequence must be followed to protect the system from damage and clogging. The first component attached is a backflow preventer, which protects the potable water supply from contamination by irrigation water.
Next, a filter is installed to remove small particles that could clog the emitter openings; screen or disc filters are common choices. A pressure regulator is then attached, which is necessary for drip systems designed to operate at a low pressure range, typically between 15 and 30 pounds per square inch (PSI). Standard residential water pressure would cause low-pressure drip components to fail without this regulator. The final piece is the swivel tubing adapter, which connects the regulated, filtered water supply to the main polyethylene tubing.
Laying the Supply Lines and Emitter Placement
Once the head assembly is complete, the mainline tubing is run from the adapter to the trees, either laid on the surface or lightly trenched. Emitters must be placed at the tree’s drip line, the imaginary circle on the ground directly beneath the outermost edge of the canopy. Placing emitters near the trunk is ineffective and encourages shallow rooting, as the feeder roots responsible for water absorption are concentrated near the drip line.
For younger trees, two or three emitters may suffice near the drip line. As the tree matures, the root zone expands, requiring more watering points. The goal is to wet 50 to 60 percent of the area beneath the canopy, often accomplished by creating a ring of mainline tubing or a grid pattern of emitters throughout the root zone. A mature shade tree may require 10 to 15 emitters, each delivering 1 or 2 GPH, to ensure adequate saturation.
Determining the required flow rate involves calculating the tree’s water needs, often expressed as gallons per day (GPD), and selecting the appropriate number and size of emitters to meet that demand. Proper spacing of emitters is important to prevent the buildup of salts, which can occur if the same soil area is constantly watered. Emitters are connected to the mainline by punching a small hole and inserting a coupling, which connects to the micro-tubing.
The total flow rate of all emitters in a single zone must not exceed the capacity of the mainline tubing and the water source, or the farthest emitters will be starved of water. Trees require deep watering to a soil depth of at least three feet to support their root structure. Therefore, each watering cycle should be long enough to achieve deep saturation. The slow drip rate and the pressure-compensating feature of the emitters ensure water infiltrates the soil deeply without runoff.
System Testing and Seasonal Adjustments
After installation, the system must be flushed to remove any debris. This is done by removing the end caps from the mainline tubing, turning on the water source until the water runs clear, and then replacing the caps. Once flushed, turn on the water supply slowly to pressurize the system and check for leaks at the fittings, couplings, or head assembly connections.
Monitoring performance includes observing the wetting pattern in the soil to confirm water is soaking in deeply rather than running off. The watering schedule must be adjusted based on the tree species, size, and current weather conditions. Frequency should decrease in cooler months and increase during hot, dry periods. Trees benefit from less frequent but longer watering times to encourage deep root growth. Before the first hard freeze, the system must be winterized by draining all water from the lines and storing the head assembly components to prevent freezing damage.