Ask Jim: “Will Silva Cells improve or be replaced with a better system?”

Ask Jim!

Here is this week’s “Ask Jim Urban” column. Jim Urban, FASLA is an expert on urban trees and soils and his recent book, Up By Roots, is the industry bible on these topics. Jim was also involved in the development and design of the Silva Cell system. In this column, which we’ve run for once a week for the past nine weeks, Jim has answered some of the most common questions he hears about Silva Cells. This is our last scheduled “Ask Jim Urban” post, although we’ll be bringing it back on a case-by-base basis in the future. If you have a question you’d like Jim to answer, please email us at Here’s Jim.

Won’t Silva Cells be replaced by a better system?

Absolutely! I have personally contributed a number of evolving principles to the effort to improve how we construct tree spaces in the urban landscape. I developed soil trenches under suspended pavements in 1980, root paths in the mid 1980’s. I proposed the concept of structural soil in 1986 and worked with Cornell eventually writing the CU Soil Specification in the mid 1990’s.

In 2003 I began a more holistic approach that culminated in publication of Up By Roots in 2008. This book looks at multiple strategies to improve the health and longevity of trees in cities. In Part 2, Chapter 6 of that book, a large number of concepts are suggested that each use different principles to achieve greater soil quality under paved surfaces.

I am working on several new concepts and assume that Silva Cells are not the final answer – we will continue to improve on them. But the fact that there will be other developments should not stop us from embracing the currently available concepts. It has taken me on average ten years to get any idea up and running. Remember fax machines? For the 15 years between the advent of fax machines and the widespread use of e mail, any company that said “no fax  for us we are waiting for something better” would have been out of business. Now my son tells me, “Dad, don’t e mail me just text me, email is so old school, I never check it anymore.”

James Urban, FASLA
Urban Trees + Soils

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