Growing Vegetables on City Rooftops

[Cross posted at European Tribune, Daily Kos, and Corrente in slightly different versions.]



Crazy?

Maybe, but we're doing it.


At the end of this post is a guide full of relevant links showing how you can do this yourself. We've also told our story using pictures at this Flickr page. Next to those pictures are similar instructions on how to do this .

Our experience has shown that this process has other benefits, namely that it builds connections in a fragmented social/political landscape. If you're trying to organize people, it's got a lot of potential. A big selling point is that it is something that can be done by individuals. You don't need to appeal for funding, attend planning meetings, or hire a budget busting number of "professionals".

If nothing else, you'll get some great tomatoes out of it.

In cities, most people can't garden because of scarce resources. The biggest being lack of arable land. Other limits are money, knowledge, time, and desire.

If you've got the interest, we can show you how to inexpensively grow vegetables using fewer inputs and in less time, wherever you happen to be. I'll be honest and say that nothing we're doing is all that novel. The individual "technologies" are there for anyone to put together. We want more people to do just that and have been posting our results to blogs with that in mind.

What exactly are we talking about?

Last summer, my friends and I grew heirloom vegetables on our respective rooftops in Chicago using homemade self-watering containers similar to Earthboxes®. What's so special about the design of the Earthboxes®? After reading that they "more than double the yield of a conventional garden using less fer..., we looked a little deeper and found that the results are scalable and they've got some numbers (PDF file) to back up the hype. With that in mind, we decided to make our own boxes using cheap, readily available containers.

Here in Chicago, as in most cities, green roofs aren't used to grow vegetables. Gardening for food production isn't part of the design scheme; if they are built at all, the roofs are sold by emphasizing their other environmentally friendly features, e.g., they reduce the heating/cooling load on a building and keep rain water out of the sewer system. Unfortunately, they are large, expensive projects and don't encourage anyone other than good government types or motivated environmentalists to participate. These containers can be put together using basic hand tools and commonly found materials. They can sit on the ground, a deck or balcony, or any roof that can handle the weight.

It's possible to do this on a much larger scale. In Montreal, a few non-profit groups have built an enviable partnership with their local and regional governments. It's something that could be done by like minded people here in the U.S. who want to make their communities greener and healthier.

I'm Convinced, How Do I Make These Things?

Before you get started, one important question to ask is "How do I know if my roof can handle the extra weight?" A builder, architect, or engineer can tell you if it's possible. Even if your roof can't support the weight, there are many creative, low cost ways that you can use these ideas to grow plants on your balcony, deck, or windowsill.

What exactly is an Earthbox®? And why is it perfect for the challenges of urban rooftop gardening? (Well, aside from the fact that they're not cheap.)

Once you understand how the original Earthbox® works you can use just about any combination of containers that does the same thing.


Here are the best plans for homemade self-watering containers that I found:

Where to start?

This (heads up - pdf) is a link that obsessively details the whole process of making homemade boxes using different types of containers.

At the end there is a planting guide taken from the Earthbox® site, along with some other helpful tips.

If you've got a bunch of 5 gallon plastic buckets, the double bucket design on pg 18-19 of the pdf works well. Here's a video on how to do it. It's what my friends Art and Heidi did, as you can see in the middle of my photoset and in these pics from her Flickr photoset.


The design I used, but wished I hadn't

Here's the link.

I'm going to change what I made before planting this spring by replacing the pvc piping with a safer plastic or other inert material. I had reservations about using pvc in the first place, see below under caveats for more.


What I should have made (the 2 tub design)

Here's the link

It's a lot easier to make and doesn't need any pvc.

You can find the fish pond baskets needed for the 2 tub design here.

Keep in mind that the height of the basket determines the capacity of the water reservoir you're creating. You probably don't want one shorter than 5" unless you're going to have some kind of automatic watering system (more on that below).


Ok, so how much does it cost?

For the box, potting mix, fertilizer, trellis and watering system, the official Earthbox® is about $110/box. The comparable homemade version is roughly $50/box, with the trellis accounting for almost half of that. Plus your time........ I think that you could get that number much lower by reworking the box and trellis design.

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A couple of caveats:

These sound pretty technical, but after you read through the above links you'll know what I'm talking about.

The plastic in most of the homemade boxes, i.e. Rubbermaid containers or 5 gallon buckets, isn't UV resistant like the official Earthbox®. You could paint them with a protective coating, but the only paint I found that will stick to Rubbermaid type plastic is very expensive. Instead, I tried to protect the boxes by putting an oversized garbage bag over them, one that doubled as the mulch cover. It's only been a year, but so far, so good. Worst case, I'll have to buy a new tub (roughly $5).

Using PVC as the screen support - as I did in my boxes - is questionable. I've asked several soil testing groups about pvc leaching into the soil, the consensus is that unless it's burned, rigid pvc is stable (though incredibly toxic to manufacture). It's the pliable pvc products containing plasticizers- things like i.v. drip bags and baby teething rings - that leach phthalates when heated. The resulting residue can cause havoc with the endocrine system. (I'm no expert. If you know about this stuff, I'd love to hear from you.) I've got plenty of links if you want them, though they're mostly inconclusive about using rigid pvc. Wikipedia says that CPVC is safe to use for drinking water supply lines, but no doubt about it, the stuff is nasty.

I'm going to replace the 4" pvc pipe screen supports in the boxes I made with heavy duty plastic disposable drinking cups.
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I made the trellis support system out of pressure treated lumber and thin wall metal electrical pipe, clamps, and wire - all cheap and available at Home Depot. It takes some basic construction knowledge and tools to put them together. The idea was to use the weight of the tubs to support the trellis system without making holes in my roof. I also wanted it to be sturdy enough to keep up year round and not worry about it getting blown off the roof. If you weren't as concerned with it blowing over, 1" pvc would work just as well and is easier to work with.

I don't have any specific links to the trellis because I came up with that, though I was inspired by this photo.

You can buy the trellis netting here.

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Last summer, watering the 30 boxes on my garage roof every day or two was a hassle. This year I'm looking to automate the process, but I haven't worked all the bugs out yet. The Earthbox® company makes an automatic watering system, but it costs about $25/box and they only work with official Earthboxes®. (Because the Rubbermaid tubs are taller than the official box the valve won't reach to the bottom of the reservoir. )

Donald 1800 is a frequent poster on the Earthbox® forum who has a great post full of pictures showing the official automated watering system at work. He doesn't think it's worth the time or expense to make your own automatic watering system.

This is a link to a DIY watering system. Because my boxes are homemade and I've got so many, I'm going to try something like it.


I used lightweight potting mix as recommended by the Earthbox® planting guide. Each of my homemade boxes used 2 cubic feet of mix (don't use potting soil, it doesn't wick water properly and your plants will die.) This year we're thinking of following Donald 1800's recipe for better potting mix/fertilizer.

Since peat is a dwindling resource, we're looking for something else to use in our potting mix. The most promising is coir, a product that comes from coconut shells. Another interesting growing medium is Gaia Soil. Though because it's made from recycled polystyrene, it might be better for decorative rather than edible plants.


A few helpful forums/blogs -

Low Cost Container Gardening Ideas

The official Earthbox® Forum.

Container gardening at GardenWeb.




If you want to see the photo essay that complements this diary, please go on over to our Flickr page, or google the phrase "Flickr rooftop vegetables".

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