Hello,

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:

pro:
lots of sunlight (around 9 hrs)
lots of space

con:
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:

PROTECT THE PLANTS FROM WIND
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.


COLLECT RAINWATER
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.


"SELF-WATER" THE PLANTS, IE. WICK THE COLLECTED RAIN INTO THE SOIL
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!


Jeremy.

Very professional, makes me jealous of your skills

The wind block isn't high enough though, the plant leaves will just grow above it and still catch wind. Also, it doesn't protect the growing medium from wind which also has a tremendous effect on evaporation (on everything actually). Better to surround your whole setup and atleast double the height.

Also, I don't think tomato plant stems are that bendy (bendie? ) to make a 90° angle without snapping, unless you make a large enough initial curve to mitigate this. Perhaps planting them in the vertical wall might help akin to a green wall planter. That way you can also cover the top to prevent more evaporaton from the growing medium.

I've never grown tomatoes myself so perhaps someone else has better growing related advice.

Thanks very much for your super-quick response Arico!

I think I should clarify that the plan is for the tomatoes grow directly horizontally out of the box that contains the soil, rather than growing upward then bending to the side. I've never seen examples of this, but I know tomatoes can be grown upside down, and of course rightside up, so I figure horizontal should be possible too. Perhaps this will address your concerns of both the stalks snapping, and the leaves growing above the windblock. Even so, you might be correct that they're too close to the top of the windblock.

Regarding evaporation from the planting medium, maybe it's not clear from the diagram but I plan to put a lid on the soil box, so the only significant route of evaporation would be through the slots that the stakes stick out of.

jeremy

That is a lot of work too grow tomatoes.Getting everything up through the trap door.I'm assuming you are young.Good luck and have fun.

I will only comment on the self-watering aspect. You may be very surprised by how much water that volume of soil consumes when allowed to suit itself. You may find that if it rains enough to keep that meager reservoir filled, it's raining enough to do the watering directly.

I've done self waterers built from oval and round goat size stock tanks that used 1/2" nylon rope (which works very well) to bring water from the bottom part of the tank that is roughly the same volume as the soil. It empties the reservoir more quickly than you would think, even with that ratio of soil to water compartments.

I also watered lines of puts from a 4" PVC pipe that ran the length of the line, beside and below the pots, nylon ropes run from the pot soil into holes in the top of the pipe, filled from an upturned "U" at the end. I would guess it, too, was about equal volumes of soil and water space. And being pots, which consumed more water, it needed very frequent topping off.

And water generally must wick up. At any time a wick has any portion of its run lower than the top level of the water, it will flow down the wick continuously and drip from the low part of the wick, not wick upward according to the soil's need.

I would consider designing so that the soil compartment sat above part of the water reservoir so that all wicks ran strictly upward. If the reservoir and soil compartment could also be one unit that can hold water, with a permeable barrier to support the soil, the ropes wicks can be run up though the barrier, the water catchment can be above the water level outside the box, and a small hole just below the bottom of the soil level will keep it from flooding in heavy rain. The hole just becomes an overflow when the reservoir is full, either from the catchment or from rain soaking down through the soil.

That can also give you a larger reservoir, and there will little or no evaporation because it's fairly isolated from the environment. Oh, and you want some way to gauge the water level. A small pore pipe down into it where you can stick a dip stick is enough, or a stick with a float, if you want to see it from a distance. The same pipe can be the filling intake when rain is short.

One of my future projects is to do one where the soil compartment fits down into the outer walls, with the water in the bottom, or is a box that sits on top of the same size water box. The ropes will just hang down into the water when the box it set back down. Major maintenance is kind of awkward right now when you can't lift the soil out. I haven't worked out what to make all that out of, so I'll probably shape the removable soil compartment to fit down inside the stock tank to rest on stops.

Thanks very much for your lengthy feedback IntheHotofTexas!

In earlier models, I'd done elaborate calculations factoring in average rainfall, reservoir area and volume, container volume, and plant hydration needs, but I admit I've gotten sloppy about that. Now that you mention it, I think the ratio of soil to water reservoir volume is way too high, and there's much more soil than necessary for just 6 plants. I'll do some research and will probably end up significantly increasing the reservoir volume and decreasing the soil volume. Another consideration is weight, but fortunately where I live in Montreal, the roofs are designed to hold up to 40lbs of snow per square foot, so I'll make sure I don't come close to that.

Regarding ensuring the wick goes up, it's not super clear from the pictures but in my current design the wick is a sheet of fabric that emerges from a slot in the container and drapes down into the water, so the water should indeed only be traveling upward from reservoir to soil. However, it is true that the base of the soil container is level with the base of the water reservoir, so I don't know if that could result in some siphoning process that would fill the container up to the level of water in the reservoir, or worse yet, simply drain the water since the container bottom isn't sealed. Do you think this could happen? If so I could elevate the box above the waterline.

I can see pros and cons of putting the soil box above vs. next to the water reservoir. Pros for soil-over-water include less space usage and strict upward wicking; pros for soil-beside-water include easier maintenance (as you alluded to in describing your design) and no need for dip stick/float (which is admittedly not a big deal). Given the ample space up there, I'm still leaning towards the soil-beside-water approach.

Jeremy.

I'm not sure, but I believe that when there is a path for water to follow by gravity, rather than capillary wicking, it will flow with gravity. It will want to equalize the water levels in the box and reservoir. And will, of course, soak the soil to whatever common level the water seeks. Should be easy to find out. If it's going to happen, it should happen even before soil is loaded into the box. Just drape the wick cloth over the side of the reservoir, wet the cloth throughout, and watch the water flow out.

I think it will do this whether the high end of the wick in the soil box is higher than water level, so long as any part of it is below the water level. It will only stop when enough water leaves the reservoir to bring the water level below the lowest part of the wick.

If the weight per square foot began to get critical, I think I would make the reservoir wider and have one end of it extend under the soil box so the wick can pass upward from the bottom of the reservoir into the soil. The wick can be a close fit with the opening for it to pass through. Closeness of the fit won't stop it wicking. My wicks pass with contact through the course nylon fabric that holds the soil.That also lets excess rainwater run automatically down around the wick into the reservoir, helping refill it or just running over when it's full.

Consider nylon ropes as wicks. They are very easy to manage when you're loading the soil or if you have to dig and can be wound around to service every level of soil at every point. The are efficient wicks and empty my reservoirs exactly as the soil demands. (Before I forget, if it hadn't occurred to you, you do have to wet the soil, really wet the wicks, in the beginning before it will draw up the water.)

Thanks for more great feedback IntheHotofTexas. I'll do a little experiment to see whether soil at water level will result in endless, wasteful wicking, and if so, will make sure the soil is higher than the water. And I'll probably go with nylon ropes for wicks as you suggest, they seem to be a commonly favoured medium.