By Johanna Silver, Sunset test garden coordinator
Jim McCausland reviewed Roots Demystified last March. I attended the Ecological Farming Conference last month and had a chance to hear author, Robert Kouric, speak about his book.
His lecture focused mainly on trees, and it blew my mind. Robert talked about many of the myths we believe about roots and how these false beliefs affect our gardening practices. We tend to think they grow straight down, or at most, as far out as the canopy reaches up above. Actually, Robert says, they sprawl outwards -– sometimes hundreds of feet beyond the canopy -- and most are found in the top in the top 18 inches of the soil.
This explains why, despite constant effort, our city sidewalks are lifted and cracked by roots that crave the rich, aerobic zone close to the top yet have nowhere to go.
He also criticized the trend found all over the country (even in our own Golden Gate Park!) of mulching heavily around the bottom of a tree trunk. Robert warns greatly against making these "mulch volcanoes" (an emerging term for this practice) because the base of the trunk can rot or become diseased.
He offered some ideas of how to help your trees thrive, including my favorite -– permeable landscaping. This allows water and air to penetrate the soil, essentially allowing the roots to breathe where there might otherwise be concrete. Permeable landscaping also absorbs precipitation, feeding roots in your garden, rather than draining away to the nearest storm sewer.
My new favorite organization, PlantSF, has pictures of permeable landscapes.
I was just in the test garden (where the only constant is change) digging up my favorite plant, an Angel's Trumpet (Brugmansia). I thought of Robert’s talk and started gingerly pulling up a root as far as I could. Sure enough, it extended much farther than I would have expected, into another bed (and that's just where it broke off).
I love science books written for gardeners. Roots Demystified is a great one. Order it here.
Common Ground in Palo Alto will be hosting Robert on Saturday, March 7 from 2:00 - 4:00. The class costs $28. To register call 650-493-6072. Check out all of Common Ground's upcoming classes here.
