You don’t have to have land, or even a backyard, to grow delicious food. Instead you can use containers – on balconies, rooftops, concrete, and the many underutilised nooks and crannies around the home or workplace. For city dwellers it can be a chance to obtain fresh fruit, vegetables and herbs, and keep in touch with nature. Here Alanna Moore explains how to establish a container garden.
A World View
Growing food in containers is not new. In one of the world’s most crowded cities, Hong Kong, vegetables grow in containers resting on the top of the floating cages used for raising fish. In Colombia, a women’s co-operative produces vegetables for a supermarket chain in tiny yards, roof tops and stairwells. Some city farmers integrate small livestock with their gardening, feeding vegetable scraps to them and using the urine and dung for fertiliser.
In Chile, a 20 square metre city farm at the Centre for Education and Technology produces an abundance of vegetables, fruits, herbs, flowers, chickens and rabbits. Crops are grown in containers stacked up in pyramids, while potted vines grow up the walls and provide shade. Such intensive gardening can out-produce even the most well-run commercial agricultural systems.
In designing a container garden, first consider climate, aspect and micro-climates, especially in winter when structures retain the sun’s warmth, and heat escapes through rooftops. Winds also may be funneled or deflected by surrounding buildings. Sun-facing aspects are best, although insufficient light can be counteracted by using full-spectrum lights or reflective material such as mirrors. Sunny window-sills provide an excellent protected greenhouse situation for container gardens. The improved micro-climate may mean you can grow winter tomatoes such as the fast growing cold tolerant Tiny Tim variety.
Strong sun and wind can be moderated by a vine covered trellis. Deciduous vines provide shade in summer and after losing their leaves in winter, allow sunlight through. Alternatively, temporary shadecloth or a movable lattice for bean crops will reduce summer heat. An exterior vine trellis will also improve the indoor climate.
If your garden is on a balcony, window ledge or stairs, the strength of the supporting structure is the first thing to consider. You don’t want a balcony of soggy pots collapsing onto the neighbours below, and so unless you have a strong balcony or roof, lightweight containers are best.
Use plastic posts, styrofoam boxes, in fact anything that will hold potting mix and allow for easy drainage. Place the heaviest boxes where most structural support is located. With basic carpentry skills you can build terraced, tiered planter box arrangements, and line them with plastic. Hanging containers such as baskets or cut up plastic bottles will utilise air space in which crops such as tomatoes are happy.
Pulleys can be a useful way to access aerial containers, while fish tanks are suitable for potted water plants, but again beware of heavy weight. Adding some small fish to the tank can control mosquitoes, while tadpoles can keep algae levels down and breed up house frogs to help protect plants from insects. Goldfish might eat the tadpoles, so very small native fish that swim around the surface would be more compatible. If sunlight does not reach ground level then there are ways to elevate containers such as building a column or tower of tyres, using a large drum or a cylinder made from chicken wire lined with black plastic. Fill your tower with compost, and to stop it from drying out too quickly, use a drip watering system.
Pumpkins (which thrive in rich, raw manures and composts), watermelons, cucumbers and grapes are easy to grow this way. They can be trained to happily trail onto a roof top from their tower, although you may have to put mesh over the roof it if gets too hot. Potatoes will also thrive when planted in a 44 gallon/200 litre drum, but you should add mulch regularly around growing plants to make harvesting easy.
Watering your garden can be a soothing activity and a time to observe the life processes of the ecosystem. It’s also crucial to water container gardens because they dry out quickly. A watering can is recommended as one of the most efficient ways to water plants or you could install an outdoor tap near your plants to allow a hose to be connected. If time doesn’t allow you the pleasure of ‘watering mediation’ you could use a soaker hose or trickle irrigation system. These are cheap, easy to set up, and conserve water. An automatic timer connected to a tap will make life easier and allow you to go away for weekends without worry. Hydrogels – also known as ‘water crystals’, a jelly-like product which provides slowly released water to plants – added to planting mix may reduce watering frequency by up to 75%.
Potting Mix and Fertilising
Potting mixes must supply the nutrients, support, water retention and drainage required by an intensive garden. Soil is not a good medium to grow container plants in, mainly due to the great weight and often high water holding capacity. You can buy or make better, lighter potting media. Compost is an excellent, well balanced growing medium. To make your own, many things can be used; the best are locally available organic wastes, such as lawn clippings, and kitchen and fruit shop scraps. Compost can be made in shady corners, in small bins, or in heaps on concrete. For seed raising, cover the compost with an inch or two (2-5cms) of light soil. Seedlings, can be planted straight into it.
A tried and proven outdoor potting mix comprises: one part coarse sand, one part well composted hardwood sawdust, and two parts composted pine bark. Peat moss, although suitable and very light, cannot be recommended, as its production destroys peat bogs. Other light components in commercial mixes include perlite, coconut fibre, vermiculite, and bagasse (sugar can residue). Worm casts, a sprinkle of rock phosphate, rock dusts, garden lime or dolomite are also valuable additives to potting mix. Use a piece of shadecloth to stop the mix from disappearing out the bottom of the pots, and mulch the surface after planting to help prevent evaporation of moisture by sun and wind.
You will need to add fertilisers for continuous production. Of the many commercial fertilisers available, few are produced in a sustainable manner. Luckily there are many books available with eco-friendly recipes.
There are three ways that fertilisers can be applied:
- Add rotted manures or rich composts directly onto the potting mix
- Scatter controlled release pellets after planting out onto the surface (there are some great organic products around, such as pelletised chicken manure)
- Liquid feeding. Diluted human urine is ideal for this (1:5, or 1:10 for delicate seedlings), used fresh around any plants except for root crops. It’s relatively harmless stuff, but avoid splashing it on the edible parts of your plants.
Comfrey ‘tea’ makes another excellent liquid feed. This is made by immersing a quantity of comfrey leaves in double the quantity of water, leaving them to soak for 3 weeks until well rotted (and the smell has gone), then diluting the resulting solution by half with more water. Weed and compost teas are also great; just soak the material a while, then strain it, and use the solution for watering.
There is a huge range of fruit and vegetables suited to containers. Generally speaking, plants with a fibrous root system rather than a long tap root are preferable. Growing a mixture of plants together in a guild (i.e. intercropping / companion planting / polyculture / stacking) will maximise the use of space while growing large and small plants together will make best use of light. Small semi-shade tolerant plants such as lettuce, mint, and warrigal greens (Tetragonia tetragonioides) will grow happily beneath taller plants and fruit trees. Other container gardening tips include:
- relay planting, with slow and fast growing crops in together
- succession planting (immediate replanting after harvest)
- saving seeds by allowing a few of the best plants to set seed
- crop rotation (to reduce disease and demand on nutrients)
Herbs and salad plants are ideal to grow. Go for small versions like Tiny Tim tomato. Plucking greens, such as rabbit’s ear lettuce, will produce over longer periods than standard varieties. Peas and beans grow well on a trellis. Most vegetables are happy in shallow containers – however, cucumbers need a deep mix, as do root crops. Other small container crops include sprouts and mushrooms which like dark corners indoors.
There are many small fruit trees such as dwarf peaches that grow to a maximum of two metres and are suitable for containers. Other naturally small fruiting plants are Cape and English Gooseberry, kumquat (eat them skin and all), strawberries, pineapples, cherry guava, Brazilian cherry, currants and passionfruit. your fruit trees – this keeps them small by pruning, and training them to grow against walls or fences along wires.
Coping with Pollution
Plants grown near busy roads may be contaminated by heavy metals, especially lead. Leafy vegetables are most vulnerable, while root and fruit crops are more resistant to heavy metal absorption; so select appropriate varieties if planting near streets.
Other techniques to reduce heavy metal contamination include:
- the generous use of compost and mulch
- maintaining soil pH levels between 6.5 and 7
- peeling root crops grown in contaminated soils
- washing leafy vegetables grown where air-borne lead is prevalent with a 1% vinegar solution
- planting a dense screen of shrubs and trees between the garden and the road
Growing Seedlings and Recycling Containers
Producing seedlings is fun, productive and inexpensive, especially if recycled materials are used. Seed trays and punnets, for instance, can be made from margarine containers. Foam fruit boxes are also good for this purpose, the large holes must be covered with a piece of shadecloth or newspaper to stop the potting mix from falling out. A nursery is not necessary for keeping seed trays, as any shady position will do. For cold conditions a foam box (without holes) with a layer of sand on the bottom to hold moisture, and covered with a sheet of glass or plastic, makes a good mini-hothouse. To protect seedlings after the shock of transplanting, or from harsh conditions, cover them with a cut-up clear plastic container, old plant pot or banana leaf.
So if you have felt restricted with no backyard, just a balcony or ‘pocket hankerchief’ of concrete leading to a back lane, containers are a small step towards freedom and the creation of green and productive havens. Container gardens also are a bonus for the restless and transient – just pack them with the rest of the furniture or give them away.