Great Leaf Roundup, 2016

Composting Leaves

The composting of leaves from the local yard waste collection, 2015

In my article on composting, I mentioned that last year I went around during yard waste collection week and carted home bags of leaves that people had left at the side of the road. These were corralled in a fenced area and allowed to decompose, at which point they were used as both conventional compost as well as a mulch on the raised beds. The bags were saved and used as sheet mulching around some new beds and will presumably be used again when the greenhouse is complete and we are building the interior grow beds.

Loads of bagged leaves

.. and it goes on like that.

This year’s yard waste collection season has just started and so this morning I went around with the trailer and the van collecting bags of leaves. What I didn’t take into account until I had made a few trips was that replacing our station wagon with a cargo van meant that I was actually carting a significantly larger quantity of leaves with each trip. The fenced area from last year was quickly filled and even after leaving some bagged leaves on top to weigh them down for a bit, then emptying those bags into the space created and putting more bagged leaves on top, it was clear that more leaf composting area was required.

Leaf bag retaining wall

Bagged leaves are used to create a retaining wall enclosing more leaves.

Fortunately, our neighbour had already provided the solution. Last year he followed suit and collected leaves for compost. Instead of creating an enclosure, he had used bagged leaves to create a bit of a wall and then filled the interior with loose leaves. Though his decomposition rate was notable slower than ours in the fencing, the idea of using bags as building blocks is fundamentally a good one. Knowing I wanted a taller wall, I modified his system slightly by stealing some fundamental principles from the construction of retaining walls. I selected bags that were tightly packed and compacted them even more. I then laid them out with their open ends facing inwards. I pressed the openings of the bags flat so that the loose leaves inside the wall would press down against the bags and keep them from shifting. Subsequent layers were built in a similar fashion.

While I have no doubt that the bags will work well as a wall, I am also hoping that leaving the open ends of the bags facing into the pile will allow the biodiversity that will develop inside the decomposing pile of loose leaves to extend its way into the bagged leaves more easily and start to break them down. Only time will tell if this will play out as I would like and whether, when the wall is taken down, the contents will already be well on their way to becoming more leaf mould.

2 responses to “Great Leaf Roundup, 2016

  • Do you have to turn the leaves over and mix them up? If so, how often? What’s the rate of decomposition? When do you start using them? Or do you use them throughout all stages of decomp?

  • There are various ways you could go about it — right up to a “hot compost” pile with lots of mixing and balancing the materials, which will reduce it to soil in a matter of weeks. We take a more passive approach. The leaves will sit there, unturned, for the year. They can be moved at any point to beds, of course, and will continue to decompose in situ. If they stay in the cage for the year they still look leafish but much more like what what you will find on a mature forest floor than on an unraked lawn.

    The interesting thing to see will be how decomposition works this year because the leaves in the main cage were placed atop the remnants of the old pile, which will still have an active ecosystem within. In theory, it should jump-start the process because the populations of little critters should be well balanced to the exact task of decomposing leaves.

    By contrast, the overflow leaves contained in the retaining wall of leaf bags was placed on top of some flattened leaf bags, which should retard the ingress of the grass but also acts as a bit of a barrier between the pile and the soil. It will be interesting to see what happens there as well, though much of that stuff may be moved inside the greenhouse fairly soon and dumped straight into new beds with a mix of other organic material we have on hand — finished mixed compost, composted cow manure and so on.