The time comes in every gardener's life when you start to hanker after a greenhouse: for overwintering tender exotics, raising tomatoes and just pottering about in. For most of us it's a substantial investment, but if you've got the time, some willing helpers and hundreds of plastic bottles, there's a much cheaper alternative: the plastic bottle greenhouse.
Richard Bennett of Sustainable Communities Initiatives designs and builds these greenhouses. He says they're the perfect project for schools:
With lots of children to help gather the bottles and wash them, it's a great re-use educational structure that really works. A standard construction of 2m x 3m will need around 1400 bottles to be collected and rinsed. The bottoms are cut off by the children with their safety scissors, two tabs are cut on either side near the top by an adult with a craft knife to stop the top bottle sliding down it.
Now it is ready to be placed in the wall. A sturdy frame is built with wires spaced at 30cm intervals up the frame and roof: the wires hold the bottle in place and it is the cross tie wire that binds it into a solid wall, closing most of the gaps. On a sunny day it can easily be 10 degrees hotter inside the plastic bottle greenhouse than outside.
Any damage from wind or vandals can be easily repaired at little or no cost, Richard says.
That sounds ideal for allotments and gardens as well as schools and community gardens: they're building one at the National Garden of Wales, too. If you fancy making one yourself, full instructions and a list of what you'll need to find, borrow and buy, are available on this PDF at the REAP site.
If you don't have enough volunteers or don't want to wait until you've gathered hundreds of bottles, another option for a cheap greenhouse is to locate an unwanted secondhand one: often people will give you theirs for free if you're prepared to dismantle it and take it away. For more advice see allotment.org.uk.
If you have less time and fewer plastic bottles at your disposal, there are still dozens of ways you can use them in your garden, as a quick glance on Flickr shows. I like to cut them into jaggedy-edged tubes and put them over seedlings as protective "slug sleeves" or cut off the bottom and bury them upside down alongside tomatoes and other thirsty plants to aid water take-up.
Any cunning tips for using plastic bottles in the garden? (Or should we be refusing to buy them in the first place?) Share your thoughts in the comments below.