Creative Urban Gardens Part I: The Shallow Bed

Why Rooftop Gardens?


• They cost little or nothing to construct, making them highly accessible to the poorest slice of the population, those that have to most to benefit from nutritious food
• They can be built almost anywhere there is an area that can support their minimal weight
• They provide either food or a source of income to a family… or both! Also, because there is no middleman all of the profits from selling the vegetables go directly to the farmer
• 
Assuming city water is available, they are not subject to sporadic and unpredictable rainfall like normal gardens
• 
They cut down on heat in the summer and work to insulate during the winter
• 
They help clean the air of an urban area
• 
They are beautiful.
• They give people a real sense of ownership over a part of their diet, and potentially their earnings as well

Little Soil, Lots of Plants 


• Usually no more than three to six inches deep
  
• Usually 1.2m (4ft) wide so that the middle can be reached from both sides, with the length depending on the strength of the roof. If very long, there can be a break every 3.5 m (roughly 12ft) for ease of access, but this is optional depending on preference
• Behaves almost exactly like a normal garden just needs to be watered more frequently. Watering is contingent on depth, meaning a garden that is three inches deep would need to be watered twice as much as a garden that is six inches deep.

Materials:


• A mix of organic materials, compost, and soil the volume of the bed.

• A sheet of plastic to go underneath the garden to protect the roof, create a root barrier, and
 retain moisture.

• Edging material to go around the garden to retain the growing medium.

• If you choose wood as your edging material, a few nails to hold it together.


Maximum Weight Calculation:
 This weight calculation is for completely saturated sand (the heaviest soil), so depend on the garden actually weighing much less. (Note: All measurements must be in meters.)


Volume (V) = Height x Width x Length

V is in cubic meters

Equation: (V x 1.7) + (0.358 x V) = weight in kilograms (kg)


Direct Seeding vs. Transplanting:


Direct seeding is planting seeds directly into the garden bed. It is dependent on having a top layer of soil or compost, but is better for crops like peas, beans, cumbers, and zucchini, and more or less necessary for crops like radishes, carrots, beets, and other root vegetables.

Transplanting is starting seeds in pots or trays indoors and later transferring the plants to the garden. It is necessary for longer season crops like tomatoes and peppers to be started because they have zero frost resistance, and their life spans are too long to fit into the growing season. Transplants also do not require a complete covering of soil or compost on the garden, which can be beneficial if weight is an issue. However, transplanted seedlings often do not have as extensive of root systems as direct seeded plants, so direct seeding is preferable when it is possible.

Next Week: How to use local materials to create a layered soil for your garden, and how to turn an old tire into a productive planter!


Happy planting!
~Otto

For more information, check out:

http://echonet.org/content/urbanGardening

Price, Dr. Martin L. Rooftop and Urban Gardening. Echo, 2010. Web. 1 Jan. 2011.