Tree Watering - feed the roots directly
If tree watering is your aim, then aim for the roots and you'll be conserving water and saving money. Most trees and bushes have relatively deep roots, and one deep root in particular - the tap root. There are a few types of trees that don't have deep roots, but they are the exception.
A good rule is to imagine the root system of a tree as the tree turned upside down in the soil. Imagine that the tap root goes as deep as the tree is tall, and the spread of the root system is as wide as the canopy. The truth is the root system often goes much deeper and wider, but this image will give you a good idea where to water.
One approach to tree watering uses plastic tubes inserted into the ground. This allows you to water down deep instead of wetting the surface and waiting for the water to penetrate the soil. In my area of the country, such an approach can work well as we have a semi-arid climate and winds. Both of these factors remove moisture from the soil with peak efficiency.
One to two foot sections of inch and a half PVC or ABS tubing, with weep holes drilled at the buried end, driven into the ground and left just a few inches above the surface can help you get water (via hose or drip system) delivered in the vicinity of the roots. With water applied under the soil, it can wick out and continue down to help feed the deep roots.
Using deep seated tubes puts the water below the surface and can encourage tree roots to establish themselves deeper into the ground to find their source of water. Most of the time a tree will do this naturally, but when vegetation of any sort identifies where water and nutrients are located, it will grow roots deliberately to get to them.
This approach to tree watering is quite useful when the tree is young, but loses it's effectiveness over the years as the tree roots quickly spread out and down. It's not sensible to continue to install new plastic tubing farther out from the base of the tree as it grows, so use this technique in lieu of a drip system when you have just a few young trees to water.
Another approach to tree watering that I use for young seedling trees is to install a drip system. The advantage of a drip system is that no water is wasted. Any water delivered through the system is dripped directly at the base of the tree. To be sure, it's on the surface, but it's not watering nearby grass and weeds, but rather directly targeting a tree. And, a drip system can be installed such that the emitter is covered, yet still accessible for examination, thus reducing surface evaporation.
Drip systems nearly eliminate runoff because they slowly drip water into the soil and this allows plenty of time for it to penetrate down deep instead of running off. Drip systems can be configured in rings as well to water around a tree or bush, so they give you options to increase effectiveness, while being very good at saving water.
If you are tree watering with a drip system, be sure to move the drip line back away from the tree as it gets bigger because the "hair" roots that are best at absorbing water and nutrients are more likely to be found out underneath the edge of the canopy and not near the base.
The last suggestion I have for tree watering is to create "catch baskets" for your trees. These are depressions in the soil surrounding the tree that allows rain water and water from your drip system to naturally collect and puddle there. This technique ensures there is no runoff, and they're easy to put in place when you first plant the tree.
Of course, tree watering isn't necessary unless you're facing an extended drought, or your trees aren't well enough established to make it on their own with natural rainfall. I don't water my 45 foot tall spruce trees because they have a well established root system that allows them to make it through the summer without any supplemental water from me.
Good luck with your tree watering, and may these tips help you save water and save money as well.
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