Drip Tubing for Trees

Tree roots grow one and one-half to two and even three times the width of the foliage above. More amazingly, this ratio is maintained throughout the life of the tree, regardless of the rootstock, species and soil.

These two trees don't understand this basic rule of thumb. The one with two circles has the right idea that trees should be watered in circles. But at least the inner circle with the beige/brown tubing is too close to the trunk. This is at least a waste of tubing. With drought tolerant trees and many other water sensitive roots can receive enough water to cause root rot. Put the emitters further out, near the dripline of the canopy. (Based on the book Drip Irrigation- For Every Landscape and All Climates.)


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Wet Spots in Your Garden

The wet spot on the surface of the soil is misleading. The wet spots are at certain intervals, but don't represent what is going on. The photo on the left shows the misleading wet spots. The drawing on the right (from my book Drip Irrigation of Every Landscape and All Climates) shows that the wet spots beneath each emitter merge to form one continous zone of moisture. The soil for the entire length of the in-line tubing is moist some four to six inches beneath the surface, depending on the soil type. Sandier soils require tubing with the emitters pre-installed 12 inches apart. While heavier, clayey soils only need emitters every 24 inches.

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Let me know what you think.Visit my web site to learn about my new book on drip irrigation and other 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

Ramblin' Roots

Sadly, few people still realize how a tree's roots actually grow. The color illustration was to advertise a local garden tour in 2009. Notice the roots don't extend beyond the dripline of the foliage. No way. As seen in the illustrations below roots extend far beyond the foliage. (The other 2 B&W illustrations come from my book - Roots Demystified. The one on the left shows the dripline as a dotted line and the roots beyond..)

When I had a landscape maintenance company, I soon discovered that in a good soil, a tree’s roots will often grow to occupy an underground area wider than its dripline. If led by available moisture and nutrition, a tree may tunnel its roots through soil space ranging from an area one-half wider than the dripline to as much as three times further. In special cases, tree roots may ramify much more than anyone would imagine. If you add a subsoil barrier such as rock, bedrock, or caliche (hardpan), a tree’s roots will wander even further beyond the canopy area in search of food. A deep sandy soil offers little resistance to growing roots and allows for root exploration of three or more times the width of the tree. And, like a gardener struggling to dig heavy clay soil, roots don’t like clay either and don’t make much headway through it, perhaps only one-half the width of the dripline.

Some more examples include:

- Poplar (Populus generosa) can ramify 77% of its roots beyond the dripline.

- Another study found that 35% of poplar trees grew roots greater than two times the distance from the trunk to the edge of the foliage.

- Colorado blue spruce (Picea pungens ‘Glauca’) grow 60% of their feeding roots beyond the dripline.

- White green ash (Fraxinus pennsylvanica) grew roots which were 1.68 times the radius of the dripline.

- In one study, the glorious magnolia (Magnolia grandiflora), had grown roots 3.77 times wider than the dripline.

- Sugar maples (Acer saccharum) produced roots that have been found spreading underground 30 feet beyond branch tips.

- The roots of honey locusts (Gleditsia triacanthos) can reach nearly three times beyond the dripline of the foliage.

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

Visit my web site to learn about my new book on drip irrigation and other 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

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