It has only been in the last year, since I acquired a very small plot of earth to cultivate, that I have begun to appreciate what can be achieved in a small space. Before this I had a container garden on the patio that I experimented with, but I have to admit, growing things in pots is so much more difficult for a novice, than growing things in the ground. Open earth does a lot of the hard work for you - it holds water and nutrients, it collects the warmth of the sun, it has a healthier balance of pests and predators. Container gardens are not like that - they dry out and deplete easily, and the pots themselves are ideal habitats for unchallenged pests - in my case, slugs.
This year, my back yard pots have been neglected. It is only now as we crawl into autumn that I have begun to fill them again and take care of the volunteer plants that have sprung up from last years seed. It seems that I will get a good harvest from a little effort - remembering to water everyday, staking and pinching out.
The situations where container gardens are most likely to be appropriate are the places that most desperately need them, for their aesthetic and habitat supplying qualities as much as the food. In the high density concrete jungle of the city, they will catch the rain, slowing its otherwise unimpeded rush across paving slabs and into storm drains. They will attract wildlife where once no creature dared tread.
Anything particularly fussy about its growing conditions can thrive in a container. For many people here in the UK, blueberries are container crops, as few have the naturally acidic garden soil they require. Tomatoes, aubergines, chillies, sweet peppers, beans, salad onions and salads will all do well. Most herbs, especially the Mediterranean natives can thrive in shallow, dry soils. There are now varieties of root vegetables bred especially for shallow container growing.
I know how disheartening it is to want to grow a sizable proportion of your own food, to be confronted with just a windowsill or patio. I spent many years not bothering, waiting instead for a patch of garden to come along. It was a long wait and we eventually made use of the limited space we had. Resist the temptation to not bother, to believe that the effort is pointless. To make things easier, start with a good book. General gardening books aren't particularly useful to container gardeners. Instead, try one of the many books suited. The Edible Container Garden by Michael Guerra is particularly inspiring and comprehensive. Books on square foot gardening, self watering containers and container 'recipe' books are also useful.
Start with the largest containers that you can; and the deepest. They will hold moisture more effectively, meaning that if you are as disorganized as me and forget to water for a day or two, the result shouldn't be catastrophic. Look for seeds and plants suitable for containers - you can buy patio root vegetable seeds and dwarf fruit trees bred to crop prolifically in small spaces. Start with something that you like to eat too - if you don't eat salad, don't grow it just because it is ideal for pots. Choose a tasty variety of tomato instead, even if it will be less productive for the same space.
If you manage to grow a pot of basil on a windowsill, you have added a little life and flavour and fragrance to your world. If you then manage a trough of herbs and salad on a patio or balcony, you have saved yourself more than a few pennies and food miles - and created a small ecosystem teeming with valuable organisms. If you then manage a grow bag or two of tomatoes, beans, new potatoes or even a dwarf fruit tree, then you may just be able to make a few whole meals out of your labours and will be well equipped for the day when that little patch of earth does come calling for you.