If you told me when I was 20 that checking the rising temperature of a pile of leaves would be the highlight of my day, I would probably have said “shoot me now.” But it has happened and I don’t regret it. Geeking out on the insanely intricate and intelligent processes of plant biology brings me serious joy. Depression and anxiety fighting type joy. This crazy world temporarily seems to make sense kind of joy.
Leaf composting is just such a process. When trees drop their leaves, they decompose and the nutrients they contain are returned to the soil. The soil in turn is made both nutrient rich for the tree to feed on but also for a host of micro-organisms that live in the soil and magically do all kinds of good things for it. Think worms and vermicomposting times a million. Mother Nature ain’t no dummy.
All that lovely flavor and nutrition you get from your vegetables comes directly from the complexity of your soil. The more you feed the soil, the happier everything is. Fertilizers, even organic ones, feed plants but they don’t feed the soil. So it delivers what is necessary to produce fruits but it doesn’t necessarily deliver everything it needs to be scrumptious or disease and pest resistant. Compost feeds your soil and the richer it is the more tasty your vegetable are but also the stronger they are to resist the bad things that come along. Of course, nothing in organic gardening is foolproof but from what I’ve gathered so far, focusing on complex soil is the best shot you have. I am trying to depend solely on compost, vermicomposting, cover crops and enriched mulch to keep my soils and plants happy. I’ll post on the rest of these practices soon.
As for leaf composting, at it’s most simple you can create a 4×4 pile of dry leaves, wet it down from time to time to keep it moist, and in time you will have gorgeous, rich compost. This takes several months depending on where you live. If you have cold winters and won’t be planting a garden for awhile this might be the easiest option and the compost will ready for you in the spring. Here in Southern California where we have a longer growing season, I want to speed up the process so I always have good compost available and can avoid having to buy expensive, lower quality options. So, I’m going for hot composting where I can hopefully create dark crumbly compost in a couple of months.
Hot composting is when you balance different materials and conditions to raise the activity level of beneficial bacteria that speed decomposition. Anything between 100 and 150 degrees is considered hot composting. The ideal temperature is around 140 to keep things moving quickly but hotter than 150 and the beneficial bacteria may die off defeating the purpose of retaining the heat. Google hot composting and you can lose an afternoon on the various approaches but since I am trying to do everything as easily as possible, this is the approach I settled on.
How to Hot Compost Leaves:
- Collect enough dry leaves to produce a 4’x4′ pile. You can also do this in stages as you collect enough materials and build the layers of your your pile one at a time. I got a couple of Geobins from Amazon to make the piles neat and easier to manage.
- Collect coffee grounds. Call Starbucks or your local coffee shop in the morning and ask them to save their used coffee grounds for you to pick up at the end of the day. I usually get about 10-15 lbs each time. You’ll need about 30 lbs total for the bin. Sometimes the baristas are thoroughly confused by this request but if you don’t mind the inconvenience of seeming like a crazy person it is well worth the effort and they get used to you after a while.
- Collect a pile of greens from around the garden. Could be grass clippings, the trimmings from bushes or old vegetable plants pulled up after harvest. Leafy trimmings are great for keeping pockets of air within the bin. The stems will take longer to break down but it’s not a big deal if they don’t. They’ll continue to provide good aeration to your soil when you add the compost to the garden.
- Fill your container or geobin about 1/3 full of leaves. Spread 10 lbs of used coffee grinds over the leaves and add a layer of greens.
- Water the layer in. The conventional wisdom is to keep compost as moist as a wrung out sponge.
- OPTIONAL: Grab a pitchfork or similar tool and mix up the leaves, coffee and greens. This will speed things up but isn’t totally necessary. And it’s kind of a bitch. So it depends on my mood as to whether I do it or not.
- Repeat the process with two more layers in equal thirds and top with a layer of dry leaves.
After about a week, your compost should get up to about 140 degrees which means activity is buzzing along. It will hover there for a few days and then begin to drop. 2 weeks after reaching 140, my pile slowly dropped back down to 120, still a reasonable temperature to keep things moving. But when it dropped to 100 I decided to take action.
Here’s the rub of hot composting. To keep it hot it needs airflow and moisture. Moisture is easy as you can dig a few inches in to check how moist it is and spray it with a hose if needed. The hard part is oxygen flow. This requires turning the compost which means mixing it all up and around to introduce pockets of air. Basically you are taking what has become compacted and loosening it all up. This is a serious pain in the ass. I did it once and and vowed never to do it again. Instead I bought another geobin and transferred the contents of the first bin to the second. In the process I introduced needed oxygen. I was happy to discover that from about 3/4 of the pile was already nicely composting. There were still leaves and stems but it already had plenty of nice crumbly soil texture and earthworms.
Transferring the pile also takes a little effort but is not nearly as annoying and much more effective than turning it. The temperature dropped to 80 but within a day was up to 90 and within 7 days it retuned to 120. If you’re not in a hurry and don’t feel like adding this step then just leave it and it will eventually do it’s thing. The time spent at that higher temperature has still benefitted the process. Just make sure it stays moist.
The compost is done when the leaves are unrecognizable and it smells nice and earthy, not rotten or damp. Take a clump of compost and squeeze it in your fist. It should hold together but quickly fall back apart if you poke at it. I don’t screen my compost because I’m lazy and internet research suggests it is not necessary when you are layering it in to your garden. Some level of chunkiness and unbroken down stems provides good aeration for the soil whereas a screened compost can become too dense and almost claylike.
I’m constantly learning about this process. I will update this post regularly when I find easier and/or more effective ways of giving your garden the goods it deserves. And by all means, if you know something I don’t about hot composting, educate me. I’m here to learn.