Thursday, February 14, 2013

Edible Rooftop Review - Part I

[Eagle Street Rooftop Farm, Brooklyn, NY]
Rooftops are one of the major underutilized spaces in cities and for this reason have long been targeted for greening efforts, from plazas and ornamental roof gardens of the early 1970s to today's rooftop farms and edible gardens. In this post I've highlighted a few of the technologies related to rooftop farming, and some case study farms that represent a spectrum of ways to incorporate farms on roofs, from technology to programming. This is only a small sample of all the urban rooftop farms out there -  if you think I missed an important one, please shout it out in the comments! If you're planning or designing a roof garden (edible or otherwise) an excellent resource is Roof Gardens: History, Design and Construction by Theodore Osmundson. For very small projects (think garden shed) Small Green Roofs by Nigel Dunnett is a handy resource. 

[Typical green roof section]

Soil-based roof gardens are classified as either extensive or intensive. Extensive gardens have very shallow soil profiles (2" or less) and can only support small, shallow-rooting plants like succulents. Extensive roof gardens mitigate urban heat effects and slow and store stormwater runoffs, but cannot support larger vegetation. Intensive gardens have deeper soil profiles, sometimes to several feet depending on the structural capabilities of the building and the plant material desired. Intensive gardens can support edible plants, shrubs and even trees depending on how they are designed. Sometimes these two are differentiated as greenroofs (extensive) and roof gardens (extensive). Planted roof systems typically consist of a number of layers designed to protect the roof itself from water intrusion, and vary most in the design of the growing medium, which must be both lightweight and able to hold water effectively. Rapid water loss to evaporation is one of the major challenges to roof garden plants. Other options for roof-gardens include planter boxes, hydroponic systems, and greenhouses.


[Gary Comer Youth Center edible roof garden, Chicago, IL]
Eagle Street Rooftop Farm, in Brooklyn, NY converted their entire 6000 sf warehouse roof into farmland, by installing an extensive rooftop garden wall-to-wall.  Crops are grown in beds of soil 4-7" deep, and sold in an on-site market and to local restaurants. The farm also runs education programs and is open to the public daily. Brooklyn Grange is a successful 2-acre commercial farm using an extensive roof garden design, also in NY. Both these farms embody the most traditional aesthetic of 'farm', as if a little piece of Kansas had been blown onto a Brooklyn rooftop.

Gary Comer Youth Center roof garden in Chicago, IL is  a non-profit in-place garden, growing 1,000 pounds of food annually and feeding 175 children at the center daily. Soil is 18-24" deep in growing areas. The garden won the ASLA Honor Award for General Design in 2010. The garden design translates traditional farm rows into a playful urban space by alternating the row sizes, and uses concrete bands between rows.


[Uncommon Ground (top) and Ledge Kitchen garden (bottom)]
Uncommon Ground is a rooftop restaurant garden featuring 28 raised cedar and steel frame planters (for 650 square feet of growing space) on a 2,500 square foot roof deck of recycled composite materials. Plants are grown in a special soil mixture. The garden was the first certified organic roof garden, and all produce goes to the restaurant. Ledge Kitchen in Boston, MA is a 4,000 square foot restaurant garden, growing produce in planters filled with a lightweight soil surrounded by recycled rubber mulch walking paths. 


[Bell Book & Candle aeroponic garden]

Hydroponics as a growing system has been shown to produce higher yields, and to use less water, than conventional growing methods. Hydroponics also make production available in places where there is no soil.  

Bell Book & Candle is a New York City restaurant with a rooftop kitchen garden growing in aeroponic towers. A mist of nutrient-rich water nurtures a whole range of crops from greens to tomatoes. Sixty percent of the restaurant's produce is grown on the roof. The aeroponic system used by BB&C is a home system, readily available on-line.

Local Garden in Vancouver is a commercial hydroponic-based farm on a parking garage roof - read more in Grow City's earlier post.

How do these different systems compare for yields, management, and start-up costs? Any graduate students out there looking for a thesis topic? Knowing how the system will effect the success of the farm, and meet it's goals, is a crucial element in designing an edible rooftop. More on greenhouse rooftop gardens, and growing systems in a future post.