By: Jo Kirwan

When we started out on our journey of discovery into the world of gardening and growing our own vegetables at Betty Cornhill community garden (BCG), a seasoned gardener gave us some advice that we haven’t forgotten! If we were not getting the crops expected, then we were either not watering enough or there was lack of good compost.

Little did we know that we would need quite so much compost!

As absolute beginners, the consensus was that things would progress faster if we built the plot from the ground up. Like many other novices might, we went to Bunnings and bought as much good quality bagged compost as we could afford. Imagine our horror when we discovered this barely covered three square metres!

Clearly, it was time for ‘Plan B’… let’s try making our own. Of course, whatever you do in your garden you’re only partly in charge – nature works in its own ways and to its own timetables, and coming up with that much ‘cold’ compost (the type you would make in a bin) was going to take many months, if not years.

After a little research we discovered hot composting and have not looked
back. It is somewhat addictive, as we are constantly on the lookout for ‘green’ or ‘brown’ materials and an area of our home backyard has various piles in different stages of development.

We follow what is known as the ‘Berkeley method’, originally developed by the University of California. It’s definitely quicker than the more common method of putting everything in a compost bin and turning it occasionally. There are several other benefits, but it’s also a more intensive process.

It is worth stressing the information we’ve provided is simply our story so far; we’ve tried to avoid getting too technical but if it gets you interested in the subject, we strongly recommend that you look online for more details.

Enjoy some of our observations to date, after some 12–15 months of following the process:

  • It is quite simple and quick to produce large amounts of good compost for the ever-hungry plants. It usually takes less than three weeks, but should then be left to settle down for a further four. Physically, it’s a really good workout!
  • With hot composting, your main aim is to make a pile which alternates between green and brown organic matter, which is wetted as you go. It seems to work well with roughly equal proportions of green and brown, although (as elsewhere in the gardening world) there is much friendly disagreement over which ratios are the best!
  • What are these ‘greens’ and ‘browns’? Well, greens contain high amounts of nitrogen— things like manure, hay, foliage and old plants (that you might be ripping out of your plot); these break down fairly quickly. Browns are higher in carbon—straw, dried leaves, shredded paper, sawdust or woodchips and are slower to break down.
  • The size of the pile is seen as being crucial to the success of the Berkeley method. The breakdown of these materials generates a lot of heat and if you can build a pile of roughly 1 cubic metre, a sufficient amount of this heat is retained within the pile. This in turn accelerates the breakdown process, as the relevant organisms thrive in the hot, damp conditions that you’ve created. If the pile is smaller than this, the benefits are greatly reduced. Some literature also says the benefits reduce if the pile exceeds 1.5 cubic metres. Given the effort required for one person to build and repeatedly turn a standard sized pile, we’ll just say that chance would be a fine thing!
  • The pile should reach 50–60°C at its centre after a week or so, meaning that many pathogens and unwanted seeds won’t survive. By that time, if you open up the pile you will see that the materials at the centre are already unrecognisable compared to the original inputs and covered with a fine white, ash-like powder.
  • Steam will also be generated by exposing the centre, it all looks a little volcanic—almost as if the compost is smouldering! The powder that appears at the centre is actually a strain of heat-loving fungus and indicates you’re probably on the right track!
  • After about 5 days, you need to start turning the pile every couple of days, aiming to transfer the outside into the middle of the pile, and the middle to the outside. There is a school of thought that turning the pile daily will speed the composting process even further, though so far ours have only ever been turned every other day, and this is easier to schedule in a busy life! Turning distributes the benefits of the process, ensuring that every part of the pile has the benefit of spending roughly equal time in the hot centre.
The perfect ‘recipe’ for hot compost! Photo: Jo Kirwan
The size your pile needs to be for the best results. Photo: Jo Kirwan
A steaming pile of hot compost. Photo: Jo Kirwan

We were lucky enough to speak to a horticulturist during a visit to Kew Gardens in London, and her take on organic gardening was interesting,and very much in line with that first piece of sage advice we received at BCG.

“Don’t dig, just keep piling it up year on year – hot composting is the way to go. Some people like to sieve the compost but I just chuck it on, lumps and all!”

Good enough for us, and results so far indicate we’re doing it right.