Change your gardening habits to help roots thrive
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Change your gardening habits to help roots thrive
Occidental, CA. 2008.
165 pp. paperback. $24.95
Finding our Roots
Review by John Wages, Permaculture Activist
ROBERT KOURIK IS FAMILIAR to gardeners and probably to most permaculturists as the author of several books on edible landscaping, irrigation, pruning, no-dig gardening, and now roots. As I began to read Roots Demystified, I found myself wondering how deep he would go and just what he could say about roots that hasn't already been written. I was pleasantly surprised.
While Kourik's explanations of the rhizosphere, the importance of mycorrhizal symbioses, and practical advice on encouraging healthy and extensive root development are important, the most distinctive feature of the book is its root diagrams. Echoing John Jeavons' figures in How to Grow More Vegetables, and probably adapted from the same original sources, these figures show the amazing extent of root growth. A carrot, for example, can have roots extending downward 7 ft. or more. We learn about the importance of lateral roots for feeding, and deeper taproots or "sinker roots" for drought-resistance. And, Kourik tells us how to encourage root growth: compost, sheet compost, and mulch. He advises careful cultivation, giving guidelines on how close and deep is safe to cultivate without risking damage to roots near the surface. Some cultivation prunes lateral roots and can encourage the development of deeper root systems. This is interesting and possibly useful information for dry summers.
An extensive chapter on vegetables includes a section on each vegetable. In 25 pages, he singles out asparagus, carrots, the brassicas, corn, lettuce, onions, beans and peas, peppers, rhubarb, and-tomatoes for special attention. Writing no doubt from his northern California experience, Kourik gives us his design for gopherproof raised beds for carrots. We learn concrete examples of why transplanting, though commonly used for tomatoes, peppers, and other vegetables, changes the root system of some vegetables like cauliflower. More practical advice comes with each section.
The root diagrams that are so beautiful I want to cut them out and frame them were drawn by the late John Ernest Weaver, for almost 50 year a Professor of Plant Ecology at the University of Nebraska. During his career, Weaver spent countless hours excavating the root systems of herbaceous plants, shrubs, and trees. Even though most of the figures in this book focus on one plant's root system at a time, Weaver's research interests included the interactions and commingling of the roots of various species. Surely he would be amazed at recent discoveries in the rhizosphere.
In addition to common vegetables, native prairie grasses are included. One of Weaver's strongest interests was the prairie, and he excavated numerous root systems across the Great Plains to come up with his root drawings of native grasses. In keeping with Kourik's landscaping interests, data on shrubs and trees are also included. Alfalfa is of particular interest. Its root system penetrates an average of 23 ft. Maximum depth of roots was an unbelievable 128 ft. Clearly, this information is invaluable in choosing a cover crop to loosen tight soils or to restore minerals to depleted soils. The reader is left wondering how much potassium lies between the surface and 128 ft. down, and how much of this a stand of alfalfa might be able to transport to the surface? Or perhaps it is mostly water that the deep roots seek out and carry to the surface.
Lawns are not left out of the discussion. A six-page chapter discusses the best grasses for low-care lawns. With emphasis on the root systems of the common turfgrasses, Kourik explains which grasses require less watering and thus can withstand drought. I for one appreciate his warnings about Bermuda grass: never plant it unless you're sure you want it. A chapter on fruit trees includes information on lateral spread of the root systems of pear, apple, plum, and cherryuseful in the design of food forests, perhaps. While spacing recommendations for fruit trees is readily available and thoroughly researched by the land-grant universities, virtually all the guidelines are for monocultures. Consideration of lateral spread, together with depth, could inform a designer of orchard polycultures on what spacing would be best between, for example, a pear and a plum tree. No doubt, much depends on soil type, rainfall, etc., but the information presented here is indispensable. The chapter on fruits includes data on water usage by various types of irrigation lines.
Almost all (95%) plants depend on fungal associations in their root zone (rhizosphere) to solubilize minerals like phosphorus so that they can be absorbed into plant tissue. The chapter on mycorrhizae is just technical enough to be interesting to someone who has already read most of what the popular gardening literature has to say on the subject. Kourik explains the difference between VAM and. AM mycorrhizal association (I'll leave it to the reader to learn what those abbreviations mean), and. which plants depend on various types of mycorrhizae. Building organic matter and inoculating with forest soils or with commercially available mycorrhizal preparations can encourage the development of healthy fungi-rich rhizospheres, particularly important in poorer soils or in soils whose pH makes nutrients less available. For example, in high-pH limestone soils, phosphorus is fairly unavailable except in the rhizosphere, where the secretion of acidic exudates by the plant-fungus symbiont creates a microenvironment where phosphorus is solubilized and absorbed. Encouraging this microenvironment would seem the first task of a thoughtful gardener or farmer on such lands, as well as on the mineral-depleted soils of America's once-rich farmlands.
Overall, the strategy is clear: build organic matter, and roots will grow. Kourik's book offers considerable food for thought on a subject we thought we already knew. Following on the heels of the fungal-association chapter, another entitled "Trees Water Their Neighbors" describes studies that document transfer of water and nutrients between neighboring trees.
Reading about his research "in a dusty agricultural library at the University of California Berkeley" which uncovered John Weaver's drawings from the early part of the 20th century, I'm left wondering how many other treasures lie hidden in the stacks. These root diagrams are treasures indeed.
An easy, pleasant read, Roots draws the reader from paragraph to paragraph and from-page to page, with Kourik's lucid writing style. I highly recommend it for gardeners who want more insight into the secret world beneath their feet.