Call me jaded, but it’s rare now that I find a gardening book that makes me understand gardening in a new way. But this week, just such a book crossed my path. It’s Understanding Roots by Robert Kourik. In it, Kourik shares the fruits of his own deep experience as a gardener as well as his research into a variety of obscure but fascinating studies of plant roots.
Particularly interesting are the portraits of root systems of tree, shrubs and herbaceous plants that were obtained by excavating and tracing roots down into the soil. Just looking at these dispels a number of gardening myths. For instance, the diagrams of a number of fruit tree root systems suggest that the traditional way of fertilizing such plants, with a circle of holes drilled under the outer edge of the tree canopies, miss most of the feeder roots that supply the trees with nutrients. And if you think you are going to dig out a dandelion taproot and all, first you should look at Kourik’s diagram of a dandelion’s roots (see below)
Kourik also includes astonishing material about the mycorrhizal fungi that partner with plant roots, hugely extending their penetration of the soil and their ability to extract nutrients by as much as 1,000 times. In addition to their beneficial effect on the individual plants, mycorrhizal fungi also link plant to plant, serving as a means of communication – if a pathogen invades one plant, nearby plants may sense this through mycorrhizal connections and activate their defense systems.
Also included are practical chapters about methods for transplanting trees that maximize root growth (I’ve also reproduced Kourik’s illustration of that), the effects of various kinds of mulch on tree roots, and the effect of gray water use on root growth (Kourik is a leading authority on gray water systems).
There are very few books that I, as a gardener, consider must-haves. But Understanding Roots is a new entry on that short list.