Flickr credit: JPHoesch
As of November 8th, the Silva Cell is officially approved for use as a stormwater best management practice (BMP) by the Metropolitan St. Louis Sewer District. According to the letter, which we are reprinting below, the Silva Cell may be used to supplement permeable pavement as a stand-alone water quality BMP. Here is the full letter: Continue reading
This tree isn’t looking so hot.
Many factors affect tree health. Are they all equally important or are some more important than others? According to Kim Coder, soil compaction is by far the biggest constraint on tree growth. In a 2007 paper, he wrote,
“Soil compaction is the most prevalent of all soil constraints on shade and street tree growth…Many people become obsessed by small constraints on trees while major life-altering impacts are ignored. Soil compaction is one of those major problems causing significant tree stress and strain, and whose impacts are usually blamed on other things. Figure 1 shows the individual items causing the greatest growth limitations for tree growth. The top three things (by far!) are soil water availability, soil aeration, and soil drainage — all three greatly disrupted by site compaction. Drought and soil compaction head the list of major tree growth stress problems” (Coder 2007) [bold added] Continue reading
Major earthworks at Heathrow’s Terminal 5. Image courtesy of Tim O’Hare Associates.
Tim O’Hare Associates LLP is a leading independent environmental consultancy based in the United Kingdom specializing in soil science and landscape engineering, including soil science, topsoil, habitat creation, sales pitch agronomy, and more. A few weeks ago I talked to Tim O’Hare himself to learn more about its reuse, recovery, and what it really means to manufacture soil. -LM
Today, most people in the landscape industry are aware of soil scientists. What was it like when you were starting out?
I started working as a soil scientist 20 years ago when landscape architects and contractors would send me a bag of soil from a site they were working on and ask me to test it. The problem was that the results that came back were very technical; people who weren’t trained in soil science wouldn’t necessarily know how to interpret them. I would therefore interpret the results in to plain language so that my clients could understand them, and also provide recommendations for improving the soil. Test results aren’t very useful if you don’t know what to do with them! Continue reading
Providence, RI. Flickr image: Harlan Harris.
When Shawn started working here, he mentioned that while he was in graduate school he had completed an assessment of Providence’s urban tree canopy, and promised to dig up the original document for us. And he did! (It’s a rough draft – we couldn’t find the final one – so ignore the occasional missing image or placeholder text). At the time that the document was written, the most recent statistics for Providence’s urban tree canopy (UTC) put it at 18 percent; Shawn and his collaborators focused on solutions for raising it an additional 7 points, to 25 percent.
The document makes a number of recommendations for ways to enhance Providence’s tree canopy. One of the most exciting for us to see – it’s like a love letter to us from the past – is a soil volume recommendation that is totally in line with the same recommendations we make: Continue reading
Tree opening, or tree pit? Flickr credit: Spacing Magazine.
I often get the following question from designers: what do I do with the space between the pavement and the street tree? Typically, it’s a small space of anywhere from 16 to 64 square feet in which the tree is supposed to live, commonly known as the “tree pit.” Really, it is an opening into another world of soil, water, and biological activity. “Pit” makes it sound kind of unpleasant, though. I prefer to use the term “opening.”
Ever seen the stomata of a leaf up close?
You know how when you learn something in school, it sounds a little abstract until you actually see it? For example, I remember learning about what stomata are. Here is the definition according to Wikipedia:
In botany, a stoma (plural stomata) (occasionally called a stomate, plural stomates)[1] (from Greekστόμα, “mouth”[2]) is a pore, found in the epidermis of leaves, stems and other organs that is used to control gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the opening… Also, water vapor is released into the atmosphere through these pores in a process called transpiration.
But have you ever actually seen stomata moving around, doing their thing? It is trippy. Continue reading
Image courtesy of Dr. Tom Smiley
Here is this year’s photo from the Bartlett Tree Lab study comparing different planting methods for urban trees. This year, we can also share a graph that demonstrates just how well the trees growing in suspended pavement are doing relative to the other treatments. Continue reading
Mountain Equipment Co-op’s green roof (Spadina, Toronto, ON). Flickr credit: padraic
In 2009, Toronto became the first city in North America to establish a bylaw requiring green roofs of new development. This bylaw has now been in effect for nearly four years; applies to new building permit applications for residential, commercial, and institutional developments of greater than 2,000 square meters.
Recently, Toronto expanded their Eco-Roof program to offer funding opportunities for buildings not subject to the bylaw – including existing residential, industrial, commercial and institutional properties, as well as new properties of the same that have a gross floor area of less than 2,000 square meters. Continue reading
The trees at the Christian Science Center in Boston are planted in the oldest suspended pavement system in the US that we are aware of. Flickr credit: izzointer
We’re exhibiting at the American Society of Landscape Architects (ASLA) show this weekend in Boston! We’re in Booth 2037.
The Expo will take place at the Boston Convention Center, and in addition to the tradeshow floor, there are a ton of great speakers on the schedule. Continue reading
Flickr credit: sahunhong
A large-canopy tree is a very beautiful thing. On this, most people will agree. But is not only beautiful—it also benefits its community. It provides shade and shelter, protects air quality, and reduces air temperatures, water runoff, and human stress. A street lined with such trees is a desirable place to live and work, and a community with many large trees is attractive to visitors, residents, and businesses.
Growing large-canopy trees is a worthwhile investment and a cornerstone of today’s movement toward sustainable communities. Yet the designers of today’s built environments and city planners tasked with creating sustainable, livable, resilient communities continually make mistakes that doom their trees to failure. We wouldn’t hesitate to condemn an engineer who designed a building without being sure the columns would support its weight. Yet we allow designers to populate our landscapes with trees that have little chance to grow to a mature canopy height. Designers sometimes even refer to small stunted tees as “mature,” either an indication that they do not know what a mature tree looks like, or that they are resigned to failure as the price of placing trees in a city. Continue reading
