Other people's gardens

Growing food on the roof

What if the greens you need for tonight’s dinner were grown on the roof of the office where you work?

Even though I work from home and can easily grow my own food, I love this idea, so was excited to meet Dr Sara Wilkinson, Associate Professor in the School of the Built Environment at UTS, who is researching urban food production.

I wrote a story for UTS Brink magazine,  which you can find here.  But let me cut to the chase. Sara’s research is looking at the barriers to rooftop food production, much of which revolve around the legalities. To leap that hurdle she is developing a template of rights and responsibilities that sets out a relationship between urban gardeners and building managers.

She has also been looking at what works best. She tested three different growing arrangements on the roofs of UTS buildings: a raised bed; a wicking bed; and a vertical garden. Of these the wicking bed proved most efficient. It was the cheapest to establish ($412 plus labour), required the lowest water use, produced the largest harvests, was easiest to transport and assemble and was easiest to garden.

Rooftop food

Bed with a view!

A wicking bed waters plants from below through a capillary action that draws water from a reservoir in the base of the container. The soil is separated from the water by a layer of geotextile fabric, and the plant roots take up moisture as needed. (You can watch Sophie Thompson from Gardening Australia building one here.) The reservoir means that watering – the most labour-intensive of container-gardening tasks – is reduced from every second day to once a week or so.

The beds were planted with a mixture of eggplant, zucchini, basil, carrots, beetroot, lettuce, chilli, capsicum, silverbeet, celery, rocket, mizuna and marigolds. Soil toxicologists studied the produce grown on the rooftops before it was harvested for consumption to allay concerns about pollution from busy Broadway several floors down. Initial results showed traces of lead, which bio-mediated out once the plants were a bit more established. Of the produce grown the silverbeet was found to give the best results for the least time and effort, which won’t surprise gardeners.

 

The next stage of Sarah’s research is to apply the findings in the corporate and commercial sector and she is in discussions to introduce food production onto commercial building rooftops in the Sydney CBD. So while it may be a while off yet, the future really may offer salad and sides from the rooftop of your workplace or apartment block.

If you’re interested in following up yourself, the City of Sydney, which sponsored Sarah’s research, has posted manuals and information on green roofs.

 

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