Pre-Plant: Planning a Roof Garden


Starting a rooftop garden requires tenacity and a good plan. Tenacity because there are more hurdles to climb in order to plant your roof, including assessing weight limits and reading the fine print of tax abatements.  If you are like me and live in a multiple-resident building, you’ve also got to present your neighbors with the pros and cons, and hope they’ll be so excited by the former that they agree about allocation of funds for your project.  Meanwhile, you have to devise a plan.

In the plan, both infrastructure and timing must be accounted for.  As a newbie gardener, I’d been nervously awaiting my seeds, and excitedly preparing to get my hands dirty.  But first, it was important to know how to proceed with 1000 square feet of roof space.

I started by consulting books and the wisdom of gardeners like the folks at Retrovore, and my other food fighter friends – in sum, an eager team of gardening enthusiasts (we’re bringing back community!).  Together we came up with some preparatory planning to create a lush, edible landscape that takes into consideration the unique planting opportunities and the difficulties presented by the roof.

For one thing, the rooftop is unprotected, and is thus windy.  To shelter our raised beds, we will need to construct a windbreak of evergreens along the sidewalls, which should be both aesthetic and purposeful.  (50 feet of young Canadian Hemlocks, $156) Fortunately, beds for these evergreens can be built from the pile of free, recovered wood currently hanging around in the back of the building. Score! But for growing edibles, planters have to be constructed from untreated wood. I’ve found a great source for salvaged, untreated wood at Build It Green in Queens, where wood starts at 15 cents per foot.

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One of the benefits of being so high up is the access the plants will have to lots of direct sunlight.  This means good growing but also a need for strategic watering, like a drip irrigation system set on a timer. Watering close to the surface will help prevent water waste, and a timer will ensure we are watering in the early morning when the temperature on wilt-worthy summer days is cool. A rain censor is an added bonus, stopping the flow after a rain.  Irrigation is one of the more expensive aspects of the garden budget, at an estimated $350, but considering my status as a green gardener who doesn’t want to kill everything, I think its a wise investment.

Another important consideration is soil.  You don’t want to haul any old dirt you find up to your roof for your garden. And if you are planting directly in the ground, please get your dirt tested.  Luckily in New York we have the Lower East Side Ecology Center, which produces compost from New Yorker’s table scraps and makes a potting soil (featuring perlite, green sand, black rock phosphate, vermicompost and coconut coir – a sustainable alternative to peat moss), which they sell to the public, and deliver! Cost for soil that can be a permanent support for our garden for years to come: $500 for 1000lbs.

The garden may seem expensive to some, at our estimate of $2000.  But we are starting from scratch, and have decided as a collective to make an investment in energy efficiency, and in the creation of a living space, where we can save money by eating what we grow.  It is my hope that Councilman David Yassky’s Green Roof Tax Abatement (an extension of the J-51 abatement) passes, allowing us to recoup 90% of our costs. But at worst, we know we are making a great investment.

Stay tuned for the next post in the Roof Garden Rookies series, where I will be talking about starting my seeds.

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View Comments (6)

  1. Wednesday, March 25th, 2009
    I love this idea. I live in the Bronx and am looking to start rooftop vegetables gardens here, but with all the rules they impose on the rooftop gardens, I got discouraged until now. Someone said that you need like a 10 foot high fence around the perimeter of the roof, in order for people to go up there. If this is true, do you think the hemlocks would serve this purpose? Thanks!!
  2. Wednesday, March 25th, 2009
    Please be assured that you DO NOT need a 10' fence! Any fence requirements that may exist would certainly be much lower than that. But if a fence is required, you'll need to put up something more permanent/structured than a screen of evergreens. When my husband and I built our roof garden, we constructed long wooden planters for the perimeters of our roof and attached panels of lattice and picket fencing to the backs, it worked really well and gave us a framework to train vines, etc.
  3. Wednesday, March 25th, 2009
    I'm so excited to see your garden, Paula. What an inspiration!
  4. Kirsten
    Wednesday, March 25th, 2009
    Wow! Sounds so exciting! I hope you'll do an update when seeds begin growing. I'm curious how you'll get 1000 lbs of soil to the roof. That will be a feat.
  5. Wednesday, March 25th, 2009
    Congrats Paula. Hoping to see your garden one day, via a tour?
  6. Saturday, April 25th, 2009
    drainage in roof garden is also important. Some info can be found here.