The tomato plant on the garage roof shakes. Suddenly a squirrel emerges and sits in plain view of my kitchen window, holding his lunch between its front paws and gnawing around in a circular fashion. Hearing my muffled yells, it quickly drops the half-uneaten tomato and makes a run for it, leaping for the fence. My blood pressure soars every time this happens, which is regularly.
Gardening on the garage roof wasn’t at the top of my to-do list when I moved into the house. There were more pressing matters, such as removing coffin-like wood-framed raised beds and way-too-many rose of Sharon bushes. Then I converted the front lawn into a veggie garden. Only after those projects were out of the way did I turn my sights to my flat-roofed garage.
I was already using the inside of the garage to store dormant fig and lemon plants over the winter. (Garages are meant for plants, not cars.) I didn’t need more garden space, but the structure was ugly. I decided to container garden on the roof even though I thought growing veggies in containers was a bother (instead of just plopping seeds or plants into the ground, container gardening requires the gardener to come up with pots and potting soil—and plants in containers need regular watering).
In the Beginning
I kept the rooftop container garden simple and inexpensive. I used large, black nursery pots the size of half barrels. Once the pots were on the roof, I simply filled them with a lightweight potting mix.
The pots were simple and inexpensive, but they didn’t look as nice as purpose-built planters so I put knee-high lattice around the edge of the container garden. Quick? Check. Easy? Check. Less ugly than before? Check.
Access was simple: a ladder. I removed it when I was done tending the garden so that my kids couldn’t get up on the roof without me. Watering was easy: I kept a hose on the roof, hooking it up to the end of my garden hose when it was time to water.
I planted okra, eggplant, peppers, and tomatoes, and they flourished. But the highlight was the fragrant, juicy Charentais melons. The scorching-hot microclimate on the garage roof was perfect for them. I no longer thought container gardening was a bother. I was addicted.
In successive years, I made improvements.
In high summer the pots needed watering twice a day. So I mulched the soil surface to reduce evaporation. I tried a variety of things, including shredded paper and wood chips. In the end, my favourite mulch was black biodegradable plastic film, which reduced evaporation and also discouraged squirrels from digging. (The sight of freshly planted soil makes squirrels want to dig, but with the black plastic film, the soil is out of sight—and out of their wee little minds.)
The biggest improvement to my rooftop garden came when I started using sub-irrigation, which simply means there is a reservoir for water in the bottom of the container. I had tried a couple of commercial planters with sub-irrigation and the results were excellent. Then a friend showed me her homemade sub-irrigation planters and explained how to retrofit my big round pots. I could fill up a reservoir every two or three days instead of watering the top of the soil a couple of times each day. The plants grew even better because they never got thirsty.
Last year, with an 11-year-old daughter eager to grow some of her 50-plus tomato varieties on the roof, I made a new batch of sub-irrigation planters using rectangular plastic storage totes. I also installed plank walkways to minimize wear on the roof.
Sold on Containers
I don’t bother planting eggplant, okra, or melons in the ground any more. They do far better in containers.
This year my rooftop crops include red okra, Charentais melons, an assortment of peppers, Cape gooseberry, ground cherry, and numerous eggplants. I had to make even more planters, as my daughter, Emma, grew heat-free jalapeño peppers in addition to her tomatoes, and my 7-year-old son, Keaton, grew mini watermelons.
Squirrels still pilfer produce. At least now my kids shriek at them, too.
Container Gardening Pointers
Animals. This year my peppers and eggplants have inexplicably gone untouched, yet a friend in another part of the city deals with eggplant-infatuated raccoons. My son and I put a wire cage around his melon planters to keep out critters. I suspect we will do the same next year for tomatoes.
Sub-irrigation. It’s a technical-sounding term for watering plants from the bottom, allowing the water to soak up into the soil. A tube allows the reservoir to be filled from above. Other common names for this sort of planter are “SIP” (sub-irrigation planter) and “self-watering.” While widely available at stores, they can easily be made from recycled materials including inverted flower pots, pails, recycling bins, and plastic water bottles. An online search will give lots of information and ideas.
Weight. If you think your rooftop planters might be too heavy for the roof, talk to an engineer. I wasn’t sure about my old garage roof but since I knew that it could take the weight of winter snow, I figured it could hold a few containers in the summer.
Feeding. Feeding plants in containers is a must. I am a busy (and forgetful) gardener, so I like a slow-release, general-purpose plant food.