Garden on Your Rooftop

Backgrounder

Are you making the best possible use of the space above your head? I’m talking about the space on top of your house – the rooftop! It’s possible to harvest lots of fresh vegetables from a rooftop garden and deliver them directly to your kitchen table.

Go up to your rooftop or out to your patio and look around. How could you make the space more useful? Can you imagine a lush garden with maize, cabbage and other vegetables flourishing there?

If you have a good supply of well decomposed compost, it’s easy to make a garden on your roof. Compost is best because it’s lightweight and full of nutrients. Soil is often too heavy for the roof.

Make the vegetable bed the same way you would make a regular garden bed. It can be any shape you like. It doesn’t have to be rectangular. You may want to form it so that it fits into a corner of your rooftop. The garden can be any length, but it might be helpful to break it up with a path every two to three metres. Each bed should be just narrow enough – about one and a half metres – so that you can reach to the middle. Try to make the best use of the space.

To keep the garden lightweight, you will want to make shallow growing beds. You can grow plants in beds that are only 8-20 centimetres deep. As a guideline remember that to make a garden bed that is 8 centimetres deep and measures 1 metre x 1 metre you will need about 140 kilograms of compost.

Another way to keep the bed lightweight is to add some soft drink or beer cans. Crush the cans and punch holes in them so that the roots can grow in and out. Mix the compost with an equal volume of these crushed tin cans. Make sure that a layer of compost covers the cans.

The cans make the growing medium looser so more air can get in and also allow you to make a deeper bed without adding much weight.

If you can’t get any cans, look around for something else that might do the same job.

If you have a sheet of plastic use it for a base. This may help prevent water from seeping into cracks on the roof. It will probably always be wet under the plastic, but that is better than having a lot of water in direct contact with the roof.

You can grow many different vegetables in your rooftop garden. Try growing the same vegetables or flowers that local gardeners grow.

Smaller vegetables such as cabbage and onions will probably work better than very tall plants such as maize or plants with a large leaf area like pumpkins.

Stay away from root crops and large vines. Root crops generally need deeper beds to grow in. And large vines, such as pumpkins, jicama or sweet potatoes need more water than they would get in a shallow bed. If you want to grow these large vines you will probably have to make a deeper bed or have fewer plants in a bed and water more often. If you take those steps then you should be able to grow vines such as pumpkin or watermelon.

These shallow beds that you make on your roof are not likely to need more water than deeper beds. But they will need to be watered more often – sometimes every day. Because they are so shallow they can’t store much water. This is the main disadvantage of a shallow bed. You cannot go away and leave it for some days without watering.

So water the beds often and add a little fertilizer now and then if you see it’s necessary. If you don’t have any chemical fertilizers then use manure tea.

As we said, the best material for making a shallow bed is good quality compost. If you have lots of it then that’s what you should use.

If compost is not available you can use things like grass clippings, corn cobs, weeds, and other vegetable wastes or crop residues you have around. Water regularly with liquid fertilizer to add nutrients. The organic matter will decompose as your garden is growing. The best thing to do is experiment with mixtures of kitchen and garden wastes.

Your city garden doesn’t necessarily have to be on your roof. You can turn any flat cement slab into a garden. It could be a rooftop, driveway, sidewalk, or a section of a parking lot.

If you’re going to start gardening on your roof, start small and expand the garden as you experiment with different growing materials and vegetable crops.