There’s Hope for Urban Design


‘Tis the season of garden seminars. Recently I participated in a thought-provoking one-day seminar on the theme of bringing nature into our cities. I spoke about hellstrip gardens, but a couple of the other speakers addressed larger-scale landscapes. After seeing their photos and hearing about so many projects that are underway or have already been developed in different cities around the world, I left feeling hopeful about the direction of urban design in this country and globally.

View of the High Line, from the book Hellstrip Gardening. Photo by Josh McCullough.

A highlight was hearing Patrick Cullina speak about his experience designing and managing the acclaimed High Line Park in New York City, a conversion of an old elevated rail line into a public “promenade” with naturalistic landscaping, plenty of paths, and places to hang out in settings from secluded to central.

While showing many photos of the High Line, including some “before” and “during” ones, Cullina made a persuasive argument for the benefits of landscaping post-industrial sites (such as abandoned railways). These sites can simultaneously reference the city’s history and provide safe corridors for wildlife and pedestrians, connect neighborhoods, open up new views across and within a city (like the views of the Hudson River and down the length of major streets from above that the High Line offers), add habitat for both plants and animals, showcase public art, inject seasonal change into urban areas, be gathering spots and stages for impromptu and other live performances, help urban dwellers connect with nature, improve the local economy through tourism and by raising property values and decreasing crime, and provide large-scale space for children that is contained and separated from car traffic. Whew! Talk about multiple benefits.

The High Line has received over 4 million visitors since the project’s first phase opened in 2009. The park has already become an icon in that city of so many iconic places. It hosts public art, live performances, parties, work sessions, food vendors, classes, and tours. It includes special play areas for kids. For a sampling of what goes on there, check out this “year in review” post from 2014 at the Friends of the High Line blog.

(And for you avid gardeners who wonder about these details, we learned that the garden areas of the park have an average of 18 inches of soil depth. Though the plantings were inspired by the vegetation that grew up during its abandonment, the entire site had to be structurally fortified and the hardscape constructed before the soil and plants were brought in. Prairie plants and deciduous woody plants dominate to provide maximum seasonal variation. Seedlings rather than named varieties were used to encourage natural variation of colors and growth habits. In other words, it’s a naturalistic design in a wholly manmade environment.)

Another notable talk was the overview of green roof designs in many different countries presented by Karla Dakin, one of the authors of The Professional Design Guide to Green Roofs (Timber Press, 2013).

The science of designing green roofs has made huge strides. Simple designs featuring  varieties of sedums have given way to broad experimenting with native and other climate-appropriate plants.

A sedum-dominated green roof at the 4-H Children’s Garden in Michigan.

Counter-intuitively, roof gardens aren’t necessarily xeriscape environments. In areas with enough rainfall, they can be watered until established then left unirrigated, but in fire-prone regions they may require monthly watering to keep the plants from going dormant and dry.

But in exchange for water spent on them, green roofs do provide significant benefits in urban areas. They can mitigate urban heat by 40 to 60 degrees! They also process stormwater and filter air pollutants, making cities healthier for us all.

Dakin pointed out that roof gardens can create communities too — both as physical gathering spaces and as projects where private citizens and public organizations work together. Like the High Line, a public roof garden gets people out of car-dominated spaces and gives them a safer open space in which to gather and linger. And like other major public projects including the High Line, a substantial roof garden requires the kind of funding that can only come from cooperation between several entities (or a really excited philanthropist).

Sean Hogan, plant explorer, designer, and proprietor of Cistus Nursery in Oregon, spoke on using native western plants in green roof design. He said diversity is important to make green roofs more self-sustaining and to strengthen the ecosystem services they provide. His average green roof project contains over 100 species.

If, like me, you are curious to learn more about these ultra-urban landscapes, the Green Roofs and Walls of the World Virtual Summit is happening THIS WEEK. Check out the list of presenters, plus there will be live Q&A sessions and many vendors, all accessible from the comfort of your own home and computer.

How the heck does this virtual event work? Here’s a little explanatory video.



  1. Victorian England dealt beautifully with urban gardens.

    Adore the High Line. A must visit site for everyone, gardener or not.

    Of greater interest, is the business model of those inventing/creating the High Line. Most horticultural pursuits, commercially, fail. Not this one. And, success rippled to property values nearby.

    What is urban, anymore? Subdivisions eaten by sprawl?

    An eco container garden seminar is coming soon to ‘XYZ’, all the buzzwords with eco, pollinators, multi-season, etc. Yet using annuals grown in greenhouses with packaged soils, irrigation, fungicides, insecticides, fertilizers, trucking required, etc. Hardly eco. Yet, attendees, thankfully limited to 40 the brochure said, will think they are being so ‘good’ to the environment.

    Garden & Be Well, XOT

    • I read about the High Line gardens and would love to see them. I’m always drawn to areas where roof top gardens and adequate green space is available.

      Agree on the comments that many rails systems are coming out and commuter bike ways are taking their place. There is a lot of good with that conversion, there is a lot of passenger train interests growing again. Still, reclaiming an unused section of service line with green space is a win for all involved.

  2. Phase 3 of the High Line which just opened last fall took a different approach. We visited just 10 days after it opened. Perhaps to reduce costs, the third section has retained many of the original structures of the railroad, including its weedy landscape. The landscape is described as “self-seeded,” which is another way of saying that it is populated by the weeds that blew into the railroad ties during its 30-year fallow period. The plant list of the High Line reflects its eclectic origins. It is a mix of natives and non-natives, including many reviled by native plant advocates such as Tree of Heaven. What is remarkable about the landscape in the third section is how similar it is to the earlier sections, which were planted. In other words, achieving a “naturalistic” landscape bears some resemblance to the weeds of a vacant lot. The final section of the High Line is no less charming and beautiful than its landscaped predecessors.

    Contrast this approach with the famous green roof on the California Academy of Sciences in San Francisco which was planted exclusively with native plants. The consultant for that project advised the Academy to plant only the plants that volunteer in the sidewalks of San Francisco. The Academy ignored his advice and now they are stuck with a maintenance nightmare that was dominated by non-native “weeds” within 18 months. See the story of that failure here:

    Peter Del Tredici of Harvard’s Arnold Arboretum is the expert on the subject of realistic gardening for urban landscapes. He was recently invited to speak in San Francisco to an audience of professional native plant “restorationists.” He was warmly received. I’d like to think that San Franciscans are slowly figuring out what will grow in a radically altered climate and a radically altered urban environment.

  3. I recently visited New York and took a brief walk on the High Line – Chicago has a similar project underway.

    Growing up with ample room to roam in woods, fields, prairie, farms and streams. I was thankful that those growing up in an urban setting would have a taste of what I loved and in retrospect took for granted.

  4. The High Line is a fantastic and beautiful place – which has changed that whole area of the city. It is a great use of a railroad line that will never be used. However, I want to point out that there may be disused rail lines that could conceivably be put into use as the idea of passenger rail travel becomes more popular – again. Unfortunately some disused tracks were turned into bike paths and it does not seem that bikers and hikers are willing to give up that space. Once I could have taken the train to Boston from my western Massachusetts town, but an essential bridge halfway there now belongs to the bikers. Happily, the passenger rail line from NYC through Connecticut cities like New Haven and Hartford to Springfield Mass and now to Greenfield and on to Vermont and Montreal is now operational again.

  5. On a trip to Sydney, I discovered a high rise building that was practically covered in grass and moss (intentionally of course) – it was beautiful. I think this kind of ‘green architecture’ is catching on.

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