Irrigation Tips: Shifting to tree bubblers

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Diagram of where bubblers are placed around a tree (above). image: Hunter Industries

This past winter provided some much-needed rainwater throughout California, but we must continue to develop ways to reduce water use due to large-scale drought conditions that impact numerous states in the West. In my column last April, I provided some irrigation tips that would help conserve water by replacing traditional sprinklers with rotating nozzles like the Hunter MP Rotator. These rotating sprinkler nozzles can cut water use up to 30 percent.

Diagram of where bubblers are placed around a tree (above). image: Hunter Industries

If you have several trees at your home, you will want to consider installing tree bubblers, which are installed close to the tree’s root zone and provides low-flow watering. In the past, watering trees with the same sprinklers used for shrubs and ground cover was very common, but there are several benefits to watering your trees separately from the other plants in your landscape, which include the following:

1. Bubblers provide continuous water at a low flow away from the base of the tree, which can prevent root rot.

2. The trickling low-flow on the surface absorbs into the ground, promoting deep root growth.

3. Misting and water loss from evaporation are dramatically reduced.

4. A dedicated watering system for your trees offers you a way for continuous tree watering even if you are required to reduce the number of days you irrigate.

The bubbler nozzles can be fastened on top of threaded fixed one-half inch risers that remain above ground when not in use, but they are also compatible with pop-up spray bodies if you want them to go underground after irrigation. There are a couple of different types of bubblers manufactured by Hunter Irrigation, which include the multi-stream bubbler (MSBN) and pressure-compensating bubbler (PCB). The MSBN bubbler can throw water about 1.5 feet, while the PCB bubbler basically lets the water “trickle” down immediately from the nozzle. I used PCB bubblers in my fruit orchard, so I will discuss my experience with that.

Pressure-compensating PCB Bubblers
These bubblers provide constant water flow at any pres

PCB Bubbler Nozzle fastened to a one-half inch threaded fixed riser

sure with the range of 15 to 70 PSI. I installed these bubblers a year ago around my fruit trees after years of using drip irrigation. I replaced the drip irrigation because the ends of the tubes were popping open on occasion, weeds were growing quite a bit around the emitters, and I admittedly stepped on them because they got covered by mulch, which led to some breaks. The bubblers are much stronger, which reduces the concern of breaking.

I used PCB-25 bubblers, which provides water flow at 0.25 GPM (gallons per minute). I installed four bubblers at each tree, which totals up to 1 GPM per tree. When considering traditional sprinklers spray can spray several gallons per minute, bubblers can save a lot of water by focusing the irrigation to the tree’s root zone. As mentioned earlier, you can install the bubbler nozzle on a fixed riser or to a Hunter Pro-Spray pop-up body. The bubblers are connected underground using typical PVC pipes that would connect to a remote control valve, which you can adjust the minutes you water from your controller.

I was not sure how the trees would respond, but I noticed the leaves and branches of the fruit trees become much more vibrant almost immediately. When it came time to harvest the citrus trees this past winter, our Oro Blanco and Pomelo grew very large and were quite delicious!

In conclusion, providing dedicated watering to your trees like bubblers will help them thrive in California’s arid climate and provide flexibility to water them when water restrictions require reductions in your landscape water use. I have been impressed with the way my trees have been responding to the tree bubblers and hope you will consider them for your trees as well!

Keiji Uesugi, PLA is the principal of the landscape architecture firm, TUA Inc. in West Covina, Calif., and a faculty member of the landscape architecture department at Cal Poly Pomona University. A licensed landscape architect with more than 20 years of professional experience, he is an expert in cultural landscapes and Japanese gardens of North America. He can be reached at keijiu@gmail.com. The views expressed in the preceding column are not necessarily those of the Nichi Bei News.

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