Rooftop Garden, 2007
[What's new in 2008 2009 2010? Our website, Green Roof Growers, has more information and the latest photos. And check out this video.]


Last summer, my friends (Art and Heidi) and I grew heirloom vegetables on our respective rooftops in Chicago using homemade Earthboxes®. [I've been told it's a good idea start calling them self-watering sub-irrigated planters and to put these little ®'s everywhere.]

There are some big ideas in those little Earthboxes®. After reading that they "more than double the yield of a conventional garden using less fertilizer, less water, and virtually no effort", 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.

"Why Bother?"

Turns out it will take more than growing some tomatoes to change the world.


One of the reasons we put together this Flickr page was to show landless city residents how they can grow a little of their own food.


Heidi would come over every few weeks and take some photos of my plants, which she then sent me along with some shots from their roof garden. I rearranged them and added this commentary.

You don't have to do this on your roof. Any place you can get enough sun works. Check out this guy's Distinguished Professor's site for some really creative, low cost ideas on how to grow plants in containers. Inside Urban Green has step by step instructions on how to turn recycled plastic bottles in to planters that can fit on a windowsill. If you've got a little more space, the Path To Freedom people will show you how to turn your urban lot into a small farm.

Here in Chicago, "green roofs" haven't been 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. We think these boxes can be used by ordinary people to reclaim a scarce resource in the city, land. They're also a great way to build connections in a fragmented social/political landscape.

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

While I've got your attention - ask your local politicians to help make these boxes widely available. A group in Montreal has an interesting program. 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.

Here are two more rooftop garden links.

The official box has a great looking automatic watering system. I'm trying to figure out how to automate the watering of all those tubs on my garage roof without spending a lot of money. Here's what I've got so far: Out of a reservoir kept full with a Hudson valve, I'd run poly tubing to each of the boxes. If I force all the air bubbles out of these lines, the siphon/water level effect should keep all the tubs watered as long as the vacuum seal isn't broken.

[It works! I don't think I can claim credit for anything new. It seems like something that Archimedes figured out a long time ago.]

Any other ideas/suggestions?


[What follows is a copy of the email I sent to a few people who asked how they could make the boxes themselves. We've since put all this information on our blog, Green Roof Growers. You can see a post on how to make these planters here.

Also, here's a list of what we're growing this year

If you've got any questions after looking this over, send me an email. If I've got an answer or a link I'll pass it on. I found answers to most of my own questions by searching gardening forums, a few are listed at the end of this. If you're in Chicago and want to stop by and see this for yourself, send an email and I'll give you the address.

Before you get started, find out if your roof can handle the extra weight. A builder, architect, or engineer can give you the answer.

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. Heidi put together a step by step set of instructions on how to make a 2 bucket planter.

Here's a good 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.

[The title is a little misleading. After reworking the scraps, I was able to make each box using one intact Rubbermaid container, and 1/3 of another one. In other words, I can make three finished boxes from four containers. It turns out that a yogurt container, more on that in a bit, is exactly 1/3 of the height of the 18 gallon Rubbermaid container. Using nylon snap ties, I attached the previously cut out center of the lid to 1/3 of the cut up tub wall. This gives you a screen that's supported on the perimeter by the cut up tub wall. Then I attached the yogurt cups to support the center.

It helps if you're using a jigsaw.

If you're still reading this and want some more info, send an email. Sorry, no pictures.]

Instead of fish pond baskets, I used some of the stash of 32 oz. yogurt containers that I had lying around. I used two per rubbermaid tub, placed side by side, drilling the sides and bottom of the containers full of 1/4 inch holes before attaching them to the rubbermaid tub.

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).

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 you could get the cost down by making a simpler trellis system.


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, LDPE #4, 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 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 a bad idea. 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 replaced the 4" pvc pipe screen supports in the boxes I made with heavy duty plastic drinking cups.

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.

[6.5.09, more info on making trellises, here.]

You can buy the trellis netting here.


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 basic DIY watering system. I've got a better idea.

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 is what we used for potting mix and fertilizer in 2007. We're thinking of changing it to Donald 1800's potting mix/fertilizer recipe .

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 lightweight growing medium is Gaia Soil. Because it's made from recycled polystyrene, it might be better for decorative rather than edible plants.

A few forums/websites -

The official Earthbox® Forum.

Container gardening at GardenWeb.

Low Cost Container Gardening Ideas

Inside Urban Green, "Modern methods of growing food, foliage or flowers for the millions of us who are not green thumbs".

Homegrown Evolution, "Vegetables, chickens, hooch, bicycles, and cultural alchemy"

If you do a Google search on the phrase Flickr Rooftop Vegetables, you'll find links to some related information that I've posted to different gardening and urban agriculture websites. Some have helpful comments. It's what I've been telling people to Google if they want to find out more about this project.

Finally, we have our own site, Green Roof Growers, where you can go for updates.


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