Containers with water reserviors have two big advantages over conventional containers: they need less frequent watering and they produce higher yields.
‘Self watering containers’ – as they are also known – have been used widely for food growing in the US and Canada for several years. (‘Self watering’ is a bit misleading as they still need watering!). Plants grow stronger because water (and air) is delivered more directly to the roots, mimicing nature and encouraging strong root growth. The problem of overwatering is eliminated by an overflow hole on the side of the reservoir.
They’re slowly becoming easier to find in the UK. One specifically designed for food growing is the Earthbox. At over £30 each, they’re not a budget option – but they look well made and Vertical Veg will be testing one out this season. Stewart also make a range.
Alternatively you can make your own using recycled materials. Various guides are avaiable on the web to help you. The excellent ‘Guide to Setting up your own edible rooftop garden‘ is free to download and includes step by step instructions. Another method is described by Mike Lieberman from New York here.
Alternatively, you can add a small water reservoir to an existing container using a large, 3 litre plastic milk bottle, a strong ice cream or yoghurt cartoon, and a piece of PVC pipe – like photo below. This is a second best option – but useful to provide a ‘reserve tank’ for your plants if you are away for a weekend or forget to water.
To make this, cut holes with scissors in the milk bottle to snugly fit the yoghut carton and piping, and drill 10 to 20 holes in the yoghurt carton to allow water to pass into the soil. Cut the PVC pipe to the height of the container – this will be your fill tube. Fill the container and yoghurt pot with soil (pressing it firmly into the yoghurt pot), and use the fill tube to keep the reservoir topped up. The water will wick out from the yoghurt pot into other parts of the container.