Sunday, June 15, 2008

The Myth of the Range of Tree Roots

The following is text from my book: Roots Demystified, Change Your Garden Habits to Help Roots Thrive.

The best book on the topic of fruit tree roots is The Root System of Fruit Plants compiled by a Russian named V. A. Kolesnikov. (As with most scientific papers, only initials are used for all but the surname.) Kolesnikov’s scientific papers appeared from 1924 until 1968, indicating that the USSR regime certainly valued his distinctive research.

Kolesnikov’s primary modus operandi for studying roots was the one he called “The Skeleton Method.” As with Professor Weaver’s studies, this method entailed precise excavation of the roots. In imitation of archaeological techniques, shovels were used first, followed by scoops and, eventually, brushes. This approach preserved more fine root hairs during excavation than the most common practice of using water forced from a hose, or even more than simple washing of the roots.

Kolesnikov’s conclusion is that fruit tree roots grow one-and-one-half to two and even three times the width of the foliage above them. More amazingly, he states that this ratio is maintained throughout the life of the tree, regardless of the rootstock, species, and soil (my emphasis added). This is clearly seen in the apple tree illustration depicted in the left side above. (Click on the image to get a better view.) Each type of fruit tree maintains a slightly different ratio of root mass to canopy. The best place for water, fertilizer, compost, and mulch is beyond the foliar dripline (canopy). This applies to most trees, not just fruit trees. The roots of fruit trees are studied more than ornamental or native trees because they are economic crops.

The illustration on the right is the misguided imagination of a graphic artist. Pretty to look at, but dead wrong. The roots in no way mirror the above-ground foliage.

The relationship of the width of a tree’s root-mass to the amount of moisture it should receive is critical. Applying water near the trunk is wasteful in any climate. In a climate that routinely experiences short droughts of a month or so up to six months (as in parts of the Southwest), drip irrigation is the most efficient way to distribute water to an entire root system.

The climate, however, need not be arid for trees to benefit from drip irrigation. In a study of established pecan trees in humid Georgia, trees with added drip irrigation showed a 51% increase in yields.

It's nuts to irrigate any other way.

Please post a comment - I want to know what you think.

Visit my web site to learn about gardening books.

NOTE: The comments section at the bottom of the post has disappeared. Click on the "___ Comments" button or the title under the "Blog Archives". Thanks, Robert


Anonymous said...

Robert, you have excellent info about roots. I, too, am a midwest transplant to CA. I am beginning a blog on edible landscaping and bees which is not yet published. I was wondering if you would allow me to link to your section about roots.

You may be the first to see what I have begun, outside of the family, if you wish, at:

Brad said...

Hi Robert,
I'm a huge fan of your work. I have a question about drip irrigation in the Midwest. Do you think that drip irrigation would make a significant contribution to growth for trees planted on a swale? I was under the impression that soil moisture is more than adequate in this situation, and I'm curious about your thoughts.
All the best,