Creating a Rooftop Garden in Toronto
September 3, 2015 7:16 PM   Subscribe

What plants would do well on our 3rd story rooftop garden in Toronto?

After some back and forth with the city they have approved our plans for our new house. The one thing they are making us change is reducing the size of our rooftop deck. Originally it was going to cover the entire roof (6.8mx8.5m/22'x28') but they made us reduce it to 10m^2/100sqf. The roof is still going to be there so we would like to put some plants on it so that we can have a nicer view from the deck and our bedroom.

Here is a drawing of the roof to help with visualizing the space. The right side is south. For most of the day it will get full sun but towards the later afternoon a big tree in the front of our neighbour's house will likely provide shade.

The plants would be in containers or on trays. We are not going for a proper green roof here.

The perimeter of the roof will be fenced/screened so there will be support for plants in hanging baskets or that can climb/run along the fence.

We have a Japanese maple in the backyard which is maybe 1.8m/6' high that we would like to put in a container and put on the roof if possible. Is this a workable solution or should we give that away to someone and get a new one for the roof?

My wife is against putting an apple tree in the front of the house, would I be able to have one in a container on the roof?

We'll still be able to grow fruits and veggies in the backyard so this garden would be more for a nice view than anything else.

We would prefer perennials but some annuals are fine too. The perennials, as well as the trees, would have to stay on the roof over the winter. The cats will have access to the roof as well so no plants that would be toxic for them.

If there's a better use for the roof you can let me know about that as well.
posted by any portmanteau in a storm to Home & Garden (8 answers total)
This is my general inclination anyway, but my suggestion would be a kitchen garden. I'm a renter with a big patio and deck and I use knock-off rolling reservoir planters (mine come from Home Depot and Lowes). Herbs, tomatoes, peppers, maybe edible flowers (marigold, nasturtium) and sunflowers (which I grew among my cucumber trellises this year and it was cool). Maybe one box of wheatgrass, mint, and catnip for the cats (and mojitos), and some lavender and verbena.

I don't know anything about containering larger trees, but apple trees are a big tree, I'm not sure that's a thing even in a big pot. The maple might do, though.
posted by Lyn Never at 7:34 PM on September 3, 2015 [1 favorite]

There are also plenty of bushes (raspberry, blueberry) that produce fruit without being a whole tree. I'm sure your architect can suggest a safe maximum density (kg/m^2) you can plan to add; remember it will have to support a plant, soil, box, and additional snow load in the winter.
posted by nickggully at 7:55 PM on September 3, 2015

remember it will have to support a plant, soil, box, and additional snow load in the winter....and also the water mass of well soaked soil (i.e.-after it rains) in an extremely large pot will be significant. Myself, I'd lean towards the tall ornamental grasses and try adding a few different things every year.
posted by bonobothegreat at 8:36 PM on September 3, 2015 [1 favorite]

There are apple rootstocks that dwarf trees to as small as ~5 feet. The variety of fruit is grafted onto the rootstock, so theoretically you could have your pick of apple variety at this size (though you'd be limited by availability, or your willingness to learn to graft it yourself).

You can put out host plants for wildlife, like milkweed for monarch butterflies.
posted by domnit at 8:37 PM on September 3, 2015

Just want to be clear and echo the other commenters: you can get small apple trees, but make sure your roof is adequate!
posted by domnit at 8:42 PM on September 3, 2015

A former coworker did corn/beans/squash one year, tomatoes the next, on his very sunny roof south of the Annex.
posted by feckless fecal fear mongering at 10:25 PM on September 3, 2015

Sempervivums look awesome once you get a mat of them going and you can get them in stunning colours, sizes and shapes and they are damn near indestructible and survive Toronto winters if they have good drainage (which will also keep your weight down). Maybe some sort of minimal living wall setup would work on the fence - maybe even just a pot and some light mesh netting - They really don't need much at all in terms of soil as they are adapted to growing in alpine rock faces. Just make sure they aren't shaded.
posted by srboisvert at 10:52 AM on September 4, 2015

Nice plan. The tough thing about perennials & trees/shrubs in containers is that they don't have the insulation of the ground to overwinter in, even at ground level. Sounds like this would be doubly true if you'd like to leave your containers above ground on this 2nd floor deck? Their roots might freeze through and they might not survive. To counter this risk, some people recommend choosing perennials / trees&shrubs for containers that are hardy to 1-2 zones colder than your own zone. By the Canadian plant hardiness map, Toronto is in zone 6. The lower the number, the colder the zone, so searching for perennials hardy to zone 4-5 might help. Your Japanese maple might not do well in the colder above ground container, since most are hardy to zone 5.

A nice hardy native tallgrass with blue-grey-green foliage & rusty plume at this time of year is Indian grass (Sorghastrum nutans). As for fruiting trees/shrubs, there are apple, raspberry & blueberry varieties that are hardy to those zones & can be grown in containers (but even container variety apple trees need some structural support as they grow). Also, serviceberry (Amelanchier spp.) is an underrated hardy tree/shrub with edible berries & lovely orange fall colour, too. Don't know about the risk to cats for these plants though.
posted by onoclea at 8:31 PM on September 6, 2015

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