Container gardening

Containers should be placed in a sunny location on a balcony, patio or similar outdoor location. Your container crops will need at least 5 hours of direct sunlight a day, and ideally 8 to 10 hours.
Placing your containers in front of a white wall or a surface covered with aluminum foil will increase available light somewhat. If possible, put your containers on wheels and move them with the sun during the day to maximise their exposure to sunlight.

Containers can be made from a variety of shapes and materials including: plastic or terracotta pots, cedar (preferably not redwood because it is in short supply) planters or window boxes, barrels, cut-off milk jugs, or even recycled polystyrene coolers. Make sure the containers are made from untreated wood and not treated with creosote or pentachlorophenol (Penta) wood preservatives that are highly toxic.

The larger the container the better. Gardening containers require more soil than indoor plants, at least 2 to 3 fists deep, preferably more. Generally, most crops need a container that is twice the size of the fully grown crop at harvest.
Whatever the material and size, all containers must have holes in the bottom to allow excess water to drain so roots do not stand in water and rot.
You will need trays or similar catch basin for the runoff water – especially if you are on a balcony with a neighbor below! Unlike lettuce or carrots, tall plants such as eggplants and cherry tomatoes will be susceptible to wind and fall over causing damage. These crops should therefore be grown in wider, squatter containers for extra stability.

Packaged potting soil is preferable because it has been mixed for this purpose, and is relatively lightweight. Soil straight from the garden is much heavier. Soilless mixtures, as the ones used to start seedlings, do not readily support vegetable roots. Also, unless you add compost or soil, because they are sterile soilless mixtures lack certain nutrients that are needed to grow vegetables.
Whatever planting soil you use, you will need to discard and replace it for next season because all of the nutrients in this confined space will be exhausted. Perennial herbs are an exception; they can be grown in the same container every 2 or 3 years and only need to be repotted as they outgrow their containers.
Fill your container with soil to a thumb-width below the container rim creating a bowl to hold water.

You should select crops that have modest root systems: eggplants, peppers, cherry tomatoes, lettuce, onions, carrots and herbs. Cucumbers and sweet potatoes can work, too. Remember that heavy and tall crops are more likely to be knocked over. For this reason, you can grow cherry tomatoes but not large tomatoes. For more information about growing a specific crop in a container, see individual vegetables and fruits.

Containers need daily or twice daily watering. Every time water the container until water seeps out the drain holes. Because of the relatively small amount of soil in a container, even when it rains, the containers will need to be watered often, usually daily. Lots of direct sun, heat reflecting off a concrete patio, and wind all contribute to quickly drying out a container.
Try to insulate your container from a hot surface using a tray with gravel, for example, and from direct sun by placing a plank of wood against the container to shield the container wall to slow down evaporation and keeping the root system cool. Terracotta pots lose water more quickly than plastic pots and will need to be watered more often. You can check moisture levels with your finger. If it feels dry, water.

Most prepared soil mixes include enough fertiliser to support plant growth for 8 to 10 weeks. If your crop grows for longer periods, use a water-soluble fertiliser per the recommendation on the package, usually every 2 or 3 weeks. Too much fertiliser can stunt or kill a plant.