Why on Earth would you want to wash off a plant’s roots? Don’t roots prefer being covered with soil?
Very often, mass-produced trees, shrubs, and other woody plants are root bound by the time they reach market. Roots can often be seen circling around the inside of the container, looking for a way out. Left uncorrected, these roots can girdle and kill the plants. Washing the roots allows you to identify the primary roots and to correct any problems.
Soil interface refers the what happens to roots when they come into contact with a different type of soil. Very often, the soil used in mass-produced plants is a soilless mixture that contains a lot of pumice and organic material. You might expect that plants would simply move into the new soil in search of food and water, but they often don’t. When this happens, the plant usually dies. The same thing can happen when you transplant summer annuals from high quality potting soil into more compacted, residential soil. [Believe me, I speak from experience!] Washing off the roots and installing the plant in new or resident soil eliminates this problem. You can do the same thing when planting vegetable and flower seedlings, just be very, very gentle.
Root washing helps you to replant the newest member of your garden or landscape at the proper depth. Bagged and packaged plants are often surrounded with extra soil. This soil is often assumed, incorrectly, to mark the proper planting depth. Planting trees at the incorrect depth is one of the most common causes of tree death. You want to be able to see the outward flare of the trunk above the soil line. Slightly too high is far better than too low.
Very often, planting holes are dug too deeply and not widely enough. Trees and their roots are best pictured like a goblet on a plate. The goblet represents the aboveground portion of the tree, while the plate represents the root system, spreading out laterally. The crown and any grafting union should always be above soil level and soil amendments are not recommended. If you suspect deficiencies in your soil, get it tested before adding anything, because too much of a good thing can be a bad thing.
How to wash roots
Now that you understand why root washing is a good idea, how do you do it?
That’s it. Now you can inspect, prune, and replant.
Finally, rather than watering your trees and shrubs (and other plants) on a calendar schedule, invest in an inexpensive moisture meter. Containerized plants should be allowed to dry out to the point that soil pulls away from the edges of the container slightly, then water thoroughly. The water-stress symptoms of overwatering look very much like the symptoms of not enough water. Don’t guess.
Help your plants thrive with root washing and proper planting depth.
You can grow a surprising amount of food in your own yard. Ask me how!
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