Garden-lovers without backyards, go vertical!
Such is the cry of a Park Slope resident who recently showed a crowd of New Yorkers (including yours truly) how to start a green roof garden. Since starting a roof garden is a bit more complicated than planting on the ground, he took us step by step through the process, including how to set it up, what to grow, and how to maintain it.
A green roof generally means a carpeting of plants on a roof, which improves the energy performance of buildings, and reduces storm water runoff. Though many urban dwellers have flowerpots or container gardens on their roofs, these aren't providing the energy savings that green roofs do.
So Jeff Hens set out to create a vegetable garden that would provide some of those benefits. While his garden far from carpets his roof, it does sit right against the roof membrane, helping to insulate his house, while providing fresh food for his family.
If you'd like to start a green roof garden of your own, here are some things that you might want to take into consideration:
Safety First and foremost, you want your garden to be safe. This isn't just about protecting those on the roof from falling off. Since roofs are generally windy places, you'll also want to protect passerbys from falling tools. So install fencing and securely tie down all equipment. Consult your local department of buildings for any necessary permits and regulations about fence height.
Weight Wet soil is heavy. So too is a foot of wet snow on top of that soil. So you'll want to figure out the sustainable weight load of your roof (consult a structural engineer), as too much load in the wrong places can cause structural damage. In most cases, you'll need to use a planting medium instead of soil.
For his wood roof, Jeff used a mix of 15% stalite permatil, 15% vermiculite, 25% compost, and 45% stalite, (available through gardening centers.) Since the nutrients have been consumed, the compost gets renewed at the start of every season, but otherwise he estimates he will not need to replace this. When it snows, he makes sure to push the snow off the beds, and hasn't had a problem with weightload yet.
Containers You'll need a container that is lightweight, but allows drainage. For maximum energy benefits, it should sit flat against the roof. Jeff uses a modular planting system designed for green roofs made by Green Grid. So that the plant roots don't burrow into his roof membrane, he lines the recycled-plastic trays with a fabric weed block. He's also seen roof gardens created in wading pools, feed sacks, and even recycled tires.
Watering In the hottest months, you'll need to be watering daily. Jeff solved the problem by running a garden hose up the side of his building, and attaching it to drip lines and a timer system. This allows him to go away for several days at a time without worrying about his plants dying.
Plants Finally, what can you grow up there? Part of it depends on your available weight load. Jeff grows most of his vegetables in an 8" deep tray, which he figures to weigh 24 lbs/sq foot when damp, and 28 lbs/sq foot when soaking wet. Even still, not everything does as well as it would on the ground. Here's the list of what he's gotten to work, and a few that failed:
| Worked | Worked with Some Caveats | Didn't Work |
| Herbs Lettuces Bush Beans Pole Beans Snow Peas Bok Choy Kale Spinach Zuchinni Cherry Tomatoes Mustard Greens | Tomatoes (some wilt problem) Ornamental Squash Chard | Carrots Peppers Collards Melons Broccoli |
Images: JHBklyn
Related: Growing Potatoes in a Bag
Copyright © 2008 Apartment Therapy
excellent guide to container gardening. the list of vegetables that worked and didn't work so well is quite helpful! :)
view sugarpond's profile
Although I love the passion here for rooftop gardening, this "how-to" guide is really misleading and may set people going on the wrong path. I love the idea of urban agriculture but the truth is, roofs are difficult places to build on and a lot of care needs to go in to ensure that leaks and load bearing issues are not a problem. A number of really important steps in the rooftop garden process were not discussed in this article.
Weight load is a huge problem. Roofs are not designed to carry this extra load and the weight calculations given here are not accurate. That soil mix is much heavier than a typical lightweight green roof soil which typically includes 80 to 90% expanded shale or clay and 10 to 20% organic material. In addition, it looks like there is a lot of other stuff on that roof that would have to be included in your weight calculations.
Water is a problem. Roof membranes have a warranty. When you put stuff on top of them without using a root barrier/protection board you invalidate that warranty. In addition, roof membranes are very susceptible to cracking and puncturing and without the necessary protection layer under your trays, you will eventually create holes in your membrane and have leaks.
Step 1 - Get a Structural Analysis to verify your roof's load bearing capacity.
Step 2 - Contact your roof installer and verify that your warranty will still apply if use a protection board.
Step 3 - Get busy planning that garden! You will be an urban pioneer! I would love to see a world where we can all create localized food networks like the gardener has done here. It's very inspiring!
view Green Roof Guy's profile
Green Roof Guy -
Thanks for the additional caveats. I agree about people being careful. As I said, they should definitely consult a structural engineer about what their roof can support.
Jeff has had his roof garden for several years and hasn't experienced any problems, but as they say, your mileage may vary.
What do you grow on your green roof? We'd love to hear more about it!
view NinaC's profile
Right now, we just have some sedum and sempervivum varieties but your post is inspiring! I especially like hearing about the plants and what was successful.
We've been meaning to try some microgreens and maybe even squash - things that are very lightweight. . .
view Green Roof Guy's profile
Very nice. You've got some great examples here.
I'd like to add one more.
A few of us who live in the city of Chicago are growing heirloom vegetables on our rooftops in cheap homemade self-watering containers.
Not selling anything, we're giving "it" away.
Here's a Flickr page we put together that tells our story. Next to the pictures are plenty of links that show how this can be done using commonly available materials and non-specialized skills. The basic design of these containers allows for "more than double the yield of a conventional garden using less fertilizer, less water, and virtually no effort".
If you don't have a strong enough roof structure, try another spot. Any place that gets enough sun works just as well; a balcony, deck or down on the ground.
Thanks for posting about this.
view Bruce F's profile
very inspiring thx!
view Lizzykewl's profile
I'm a garden lover but unfortunately I live on an apartment and I don't have a backyard and not even on the roof I can't do it. But still I'm happy because in my neighborhood I have a park full of flowers and trees. Every night I'm relaxing by taking a late walk with my wife.
_________
mesa physical therapy
view EddieSmith's profile