Deep-root Watering and Feeding Trees

Photo: Randy Lemmon

At least once every hour on GardenLine, I hammer home the importance of deep-root watering and feeding trees. Listeners call because their trees haven't grown much since they planted them two years ago. Or they call about the roots of older trees coming out of the ground. These are examples of trees in dire need of deep-root watering and feeding.

The key is in developing holes in the earth above the root system that go down 18 inches. They can be developed with a Ross Root Feeder, a soil auger, a post-hole digger or a tool you've designed yourself using something like a piece of steel rebar.

The bigger the holes, the fewer you will need. With smaller holes, like those made with tools like the Ross Root Feeder, the more you will need. If the holes are bigger than an inch in diameter, however, you will need to fill them with pea gravel or organic matter like mulch or compost. Smaller holes Mother Nature fill gradually and naturally.

With the holes in place, nature and your watering system will provide plenty of moisture to trickle down the holes. You don't have to water each individual hole. The same holds true for feeding, but if your holes are two inches in diameter or more (like post-hole size), you can soak those areas individually with organic foods or soil activators. With small holes, soak the entire area with a spray-on organic liquid. Or, use compost over the surface to slowly work its way down.

Here are a some additional tips:

  • Remember that your holes need to be both inside and outside the drip line. Start them at least two feet from the trunk of the tree.
  • Remember how tree roots grow. Often, we picture them growing only laterally, but they will actually grow down in well-watered, organic soils.
  • Remember that this process is must be continuous. Even healthy mature trees will benefit from deep-root watering and feeding.

And here are some words of warning:

  • Just feeding with granular synthetic food actually eats up beneficial microbes that we want to increase down in the root zone. That's why I emphasize using organic foods for the roots of trees.
  • If you're augering with a drill bit bigger than two inches, it's wise to have gas, phone and other utility lines marked prior to drilling.
  • Don't forget to add additional holes outside the "drip line" as the tree matures.
  • Hire a tree service company if you think this is too much work.

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