Self-watering wind-protected rain-fed rooftop planter design.

Montreal, Canada


I'm a novice gardener making my first attempt at growing tomatoes in my condo. I live in Montreal, Canada, where the growing season is approximately April to October. I've already begun growing tomatoes on my balcony, but the space is limited so I want to migrate some of them to my rootop.

My roof has pros and cons as a gardening site:

lots of sunlight (around 9 hrs)
lots of space

very windy
awkward to access (ladder through trapdoor), esp when transporting materials, including water

I work in computer animation and have used 3d software to design a planter setup that is intended to do the following things (please see attached images):

The tomatoes are grown horizontally along stakes elevated 1' from the ground and surrounded by panels made of corrugated transparent plastic mounted on wooden frames. These panels block the wind but let the sun in.

Next to the box that contains the soil, rainwater is collected in a tray made of a wooden frame covered by a tarp (brown). This is in turn covered by another tarp (blue) that is suspended over the collection tray to prevent evaporation, and slanted to prevent water buildup. NOT SHOWN (because it's difficult to model): the blue tarp comes down on the sides and tucks into the tray, so there is no opening for the water to evaporate. Water runs off the blue tarp and collects in the tray. Note that there is also a ramp (support for ramp not shown) that drains into the tray, but I'm not sure if I'll use that in the end because it might be difficult to pin it down and prevent it from being blown away.

An absorbant fabric (pink) - perhaps a towel - wicks water from the collection tray to the soil box, ensuring that the soil is always moist.

This design is not intended to be 100% self-sustaining; I will have to prune suckers + monitor the plants, and I will likely need to manually top up the rain in the tray if it doesn't rain for a long time, but the idea is to have it as low-mainenance as possible.

Here are my questions:

Does this general design seem viable?

Currently the six plants are spaced 16" apart. Is that a good distance?

Currently the box containing the soil is 8' long x 1.45' tall x 2' wide, = 23.2 cubic feet, which is 3.87 cubic feet per plant. Is that sufficient soil in the container?

Currently the stakes are elevated about 1' above the ground. Is that a good amount of space to prevent them laying on the roof surface? Or can I just forgo the stakes and have the plants spill across the roof within the wind-protected area?

Please feel free to let me know any other concerns or improvements I could make.

Thanks very much!


This message was edited Jun 24, 2020 7:55 PM

Thumbnail by jeremyeliosoff Thumbnail by jeremyeliosoff Thumbnail by jeremyeliosoff
Ottawa, KS(Zone 5b)

Hello Jeremy,

I am not sure you can grow tomatoes horizontally. You might want to experiment with that on your balcony. The roof appears white in your first photo. Is that the case for the actual roof ? Grin. You might want to wear some clothes while working with your tomatoes.


This message was edited Jun 29, 2020 11:05 AM

Montreal, Canada

Ha ha, yeah don't mind the buff naked standin, I'm next to a huge office building so will def wear clothes!

The roof isn't actually white, it's covered in gravel so it's light grey. Why do you ask? I guess it matters in terms of lighter = less hot and more light reflected back at the tomatoes.

I must admit I hadn't even googled whether it's possible to grow tomatoes horizontally, but doing so does reveal a few examples, eg:

Thanks for the feedback!


Ottawa, KS(Zone 5b)

Hello Jeremy,

" The roof isn't actually white, it's covered in gravel so it's light grey. Why do you ask? "

I just wanted to make sure it wasn't black tar.

That link does show tomato vines trained and supported horizontally in Nigeria. That is very unusual. I have never seen tomatoes grown like that. Those vines must have been very long to be trained like that. The examples where the tomato plant was planted horizontally resulted only in horizontal underground orientation.

You will probably want to use an indeterminate tomato variety to get a longer horizontal plant. Some tomato growers adopt a practice like grape vine growers, and graft their tomato vine onto a special root stock tomato variety. That is a complication you probably don't want to add to your project.

" Currently the six plants are spaced 16" apart. Is that a good distance? "

Sixteen inches would be rather close spacing of tomatoes in a garden, but your scheme is so novel that the normal rules don't apply.

"...which is 3.87 cubic feet per plant. Is that sufficient soil in the container? "

It could be. I am not sure you want to use actual "soil" in your project. You might want to use something like Premier ProMix, which is a peat moss based product (of Canada). I use ProMix for my indoor gardening. You do need to use soluble nutrients with ProMix, because it has a small nutrient content sufficient only to get the plants through a seedling stage.

Growing tomatoes can be a bit of a challenge under conventional gardening circumstances. Your project adds additional challenges. Good luck with it. You may need it.


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