For organic gardeners in cities with limited space, growing food in containers is a solution, but its important to understand the challenges, so you can get the best results. My blog this week talks about some of the main challenges which relate to soil fertility, plant selection, ideal containers and watering.

Soil fertility

Fertile, living soil is the number one criteria for a healthy and productive organic garden. A garden that is connected to the ground can draw up minerals from a long way below the surface, can attract creatures that live in the soil such as worms, and can be sensitised to drawing in more nutrients and life forces by other plants living in the soil near the plants being grown. You can use crop rotation in garden beds to also naturally improve soil fertility. With all these processes, you should end up with continuously improving soil.

With container growing, most of these natural processes are not available to the gardener. So its vital to recognise that your soil in containers will never be as good as soil in the ground, if it had the same attention, and the soil in containers will not continuously improve. Once you have come to that realisation, what can you do:

• Start with a healthy soil mix in the container, not just commercial potting mix. The ideal is for some of the soil mix to be well made compost from your own composting process.

• Don't attempt to grow plants that need high soil fertility

• Add organic liquid fertiliser to the soil more regularly then you would in a garden bed. You can make some of your own liquid fertiliser by growing stinging nettle and comfrey.

• At the end of each year remove the soil from the container and replace with a new soil mix that has compost. Don't dispose of your old soil, use it in your compost process with plant, vegetable scraps and some animal manure to add life back into the soil.

If you choose to grow fruit trees and perennial herbs in containers, removing the soil each year will be challenging, especially for fruit trees which have a big root mass. Removing soil when your annual vegetable crops are finished each year will be quite easy.

Plant selection

You can grow vegetables, herbs and fruit trees in containers. With your plant selection, apply the following guidelines:

Vegetables and herbs

• Select plants with a high yield per space, ideally plants that like growing on a climbing frame

• Select plant that are easy to grow and do not require high soil fertility

• Select plants that do not take up too much space

• Always plant in season for your location

Fruit trees

• Only choose dwarf varieties

• Select the best varieties for your climate

Ideal containers

Containers can be made from clay, ceramic, plastic, wood or metal. Clay and wood containers tend to breath more than the other materials and allow better transpiration of water, reducing the potential for water-logging. Denser container material will hold heat longer which helps seed germination.

The ideal container size depends on what you intend to grow. Here are some tips:

• Fruit trees with a large root mass will need much bigger container than herbs or vegetables.

• Herbs and small leavy plants with a shallow root mass only require small containers

• Vegetables, especially root vegetables, require a reasonable depth of soil and will demand large pots

• Don't select pots which are so large that they are too heavy to move. Once of the key benefits of container growing is that you can move pots around to make the most of the sun or protect them from the cold.

Watering

You should have a layer of gravel at the bottom of the container and a drainage hole. Sit the pot on a material that enables the water to drain out properly. Maintaining ideal water conditions in container growing is quite a challenge. The soil mixture in a container can dry out quickly, compared to a garden bed which can access water from a long way below the surface. Conversely, the soil in the container can easily become water-logged, so over watering is also a common problem. Its OK to let the surface soil of the container be a little dry, test below the surface with your finger to feel moisture levels.

Conclusion

Our Gardener subscriber site can help you with container growing as it includes:

Vegetables and herbs:

• Container growing search

• Ease of growing search

• Yield per space search

• Instructional content on container growing

• Local climate planting guide

• Dwarf varieties for all fruit tree crops

• Local climate planting guide

Author Peter Kearney – www.cityfoodgrowers.com.au