Short answer, no, it’s not necessary. Neither for compost nor leafmold. But it speeds up both. I don’t even own a shredder and compost still happens. Btw both bacteria and fungi are at work in compost, as well as invertebrates.

I cold compost leaves and they break down just fine but it does take a couple of years.

I only shred those that I'm going to use as mulch.

We never add green or brown to this pile- I have another long term pile where I toss woody debris. We never turn it, water it, or anything else- I just use up as much as I can possibly use up each year then toss new leaves on top.

I don't shred anything. I think slow and steady is a nice way to go.

Shredding only speed's the process.

Thanks, all. The thought just came to me that if the other ingredients I'll be putting in the compost pile - food waste, grass clippings, weeds, spent flowering stems, shredded paper - would decompose in, say, x number of months, but the unshredded leaves would take two years, then the leaves will definitely be the limiting factor for not just the speed of decomposition but also the temperature the pile can achieve. I'm imagining that to achieve the highest possible temperature (which is important to kill weed seeds and for any number of other reasons) it's best if all the ingredients in a pile decompose at roughly the same rate. I'm concerned that the presence of whole leaves in a compost pile could limit the temperature the entire pile could achieve.

I'd be very glad to be told where I'm wrong in my thinking.

The leaves won’t take two years in a mixed heap. In fact pure leaf mold doesn’t take that long either, at least not in my climate.

Leaves take longer, unshredded, in a big pile on their own. BTW also depends on species and conditions - I find large maple leaves mat, for example. The 'limiting factor' is most likely to be nitrogen (mixed piles will help with this), air (turn frquently and/or shred), or water (depends - too little water is bad, too much means not enough air).

But most of this is whether your limiting factor is impatience or laziness - for me it's laziness. I can wait.

Thanks, all - much appreciated. As I'm thinking this through, I guess my main concern is not so much the length of time the compost pile with whole leaves takes to decompose, but the temperature I can achieve in the pile if the whole leaves are taking longer than the other ingredients to decompose. I do have a sense (maybe completely wrong!) that if the various ingredients in the pile are decomposing at a differential rate, the bacteria won't be able to work together at maximum efficiency throughout the bulk of the pile, and therefore the temperature won't get up to the optimum level (to kill weed seeds, etc.)

Most of the leaves that I'll be putting in the pile are large maple leaves, so yeah: maybe the issue of matting mentioned by armoured is another reason they might take longer than the other ingredients.

Will you be turning the pile?

I want to say I'll be turning the pile since I know it's important, but i just went through my first season of having a compost pile and I never once turned it, so I'm not sure I can break my bad habit of laziness. I just never got the hang of how to turn such a large volume of material. But that's an important point - I guess if my goal is to achieve a high temperature, turning sure does facilitate that, doesn't it?

A separate thought: I wonder if using whole, unshredded leaves within a mixed browns-and-greens compost pile allows for better aeration within the pile than using shredded leaves within the same pile? (Hmm..or maybe worse, if they mat up?)

Dry leaves aren't going to get hot regardless what you do. If you have green material to mix with them,the pile will heat but must be turned periodacly to keep heating. Less labor is required for a 3 bin system or simply moving pile each time it's turned.

Rick, I’m in NY, where it’s one zone colder and probably wetter than your MA z6. I do lazy, no turn, cold compost piles. When I go through the effort to shred fall leaves, I prefer to use them as mulch that will break down quickly. Otherwise, I use whole leaves in thick layers in my compost piles, with layers of wet/greens/nitrogen between… leaving small twigs in the leaf mix will help keep it from matting. Even my unmixed cold compost is ready to use in just one season — I’m currently emptying the piles I made in spring.

There's no need to turn a compost pile, except to speed up the process. Some people (me) just like to flip a pile. I also always keep a leaf mould bin for whole leaves, because I get more leaves than I can compost. It's just there. I don't think about it or do anything to it, except add leaves to it annually. I will occasionally rob it for to cover the kitchen scraps in a compost pile. It's at least three years old and I'm harvesting it now.

A lot of people just run a compost pile only as a means to deal with household waste. My mother, who never so much as planted a marigold or plunged a spade into garden soil, made several yards of compost annually without lifting a finger. Once or twice a day, she sent my brother or me out to the "mulch pile" with a pail of kitchen scraps. The same place where the kitchen scraps went is where my brother took the grass he mowed and the leaves he raked. Never once after my father, the gardener, died, did it even occur to us that we could harvest the bin contents.

I really want to buy a chipper right now---to try to deal with the saplings popping up all over in my blueberry field---but I've talked myself out of it because I'm finding few areas in my life where I can address my personal unnecessary use of fossil fuel. If I start piling up those saplings now in bare spots in the field, the process could be done without gasoline.

Just writing this, I've almost talked myself back into it. Those bare spots could really benefit from a thick pile of chips.

The discussion should spend some time on why you have unshredded leaves and how to shred them even more. Unless your home is on a totally paved lot where you have no reason to compost you likely have a lawn and mow it.

You can use the mower to shred the leaves and you can use it chop them into dime size pieces with a lot of of dust. If you rake your leaves and don't have a bagger you can still use the mower to create windrows of leaves which you then rake up. This way you get the benefit of the grass adding its green matter to the compost.. If you use a mower with a bagger you could still take the bagger off and run over the leaves to get them chopped finer. You might want to consider running thru the middle of the lawn and chop that first. Also run around any beds and the edge of paved surfaces before you rake or blow the leaves from there. That will keep you from having unmanageable piles to mow. If you want a smaller leaf size go over the entire lawn without the bagger attached. Maybe multiple times. Then put the bagger on and clean it up. I'd recommend bagging out the entire lawn.

Whether you're raking it up after mowing or chopping and bagging you'll be making much smaller compost piles; but you'll make less trips to the compost piles and the piles won't shrink as much.

To get the dime size pieces I let my bagger fill up and then keet going thru the lawn working toward the center. Since the bagger is full you'll be picking up leaves and clippings and pushing them to the exhaust side of the mower deck where they'll fall to the ground. Work in a circular/oval pattern pushing those leafs to the center by overlapping the last pass so that they get picked up again and shredded some more. With this method you'll be able to sit on your mower and do the entire lawn no matter how thick the leaves are; well almost. One disadvantage of this method is that there will be a brown color to the lawn from the dust but this will build up your soil over the years.

Many thanks to everyone. I actually do own a decent Worx leaf shredder which I used last year, but it sure was a lot of work to shred 30-some-odd yard waste bags of leaves (many bags picked up from neighbors' curbs, thank you very much). At the time I intended to use the shredded leaves as leaf mold but as this season went on I realized I needed more brown material for my (separate) compost pile, so into that pile went all of last fall's shredded leaves. I'm trying to think how I want to handle this year. All other things being equal, I'd prefer to not use the shredder simply because of how much work it was, but I do think that the fact I was putting shredded rather than whole leaves into the compost pile during this season helped the pile heat evenly and nicely -- but honestly I'm not entirely sure, and I appreciate the suggestions that that may not be necessary.

I guess when I do fall cleanup over the next month I'll mix some of those leaves with fall cleanup material, but I also will need to reserve a lot of them (whether whole or shredded) over the winter for mixing into next year's compost pile as all the grass clippings and kitchen waste will need the leaves as good brown material.

It's fun being a gardener - so many things to learn.

I just generally do a mix - I shred what I can with a vaccum/blower thing, and just rake up the rest. What I have done some of is pile up the leaves (when not enough time to shred and pile, or if someone else is helping, they pile and I shred later); the limit tends to be how wet the piles of unshredded leaves get, a nightmare to shred then. In future I'm going to try covering the piles to keep them dry and shred once in a while when I feel like it, it's much less burdensome when it's just exercise with tools.

Again with maple leaves (my experience anyway) - shredded will heat up nice, unshredded if damp will mat - that sounds like what you're getting. It also makes an enormous difference in how much space the piles take (not kidding about 10X reduction) and how soon it's ready.

All that said though - my base case, go-to method is to pile them up and forget about them, mostly.

Side note about the utility of shredded leaves (by lawnmower or otherwise) - they are easy and nice to dispose of a bit at a time in the garden or lawn or wherever, whenever you feel like a light bag or a bucket or two can be spread, if you notice the soil is thin or the mulch receded a bit much or been washed away, or perhaps someone doesn't like the way some mulches look. When I do this right, a bit of mulch here and there is hardly noticed, and a bit spread on parts of the lawn, very lightly raked or before/after mowing just disappears after a rain, for example, it all seems gone and feeds the worms.

This is not quite the laziest approach but a tiny bit of work once in a while when you need fresh air and aren't in a rush feels just about the same as no work at all.

"This is not quite the laziest approach but a tiny bit of work once in a while when you need fresh air and aren't in a rush feels just about the same as no work at all."

Yea,that sound's about right and in my case you might say it's a way of getting something done before my get up and go get's up and leave's me.

Shredding even a little makes them decompose a lot faster. Its not necessary to turn every leaf to confetti;even crinkling makes a difference.

I use a large plastic garbage can and a string trimmer. a couple of times through the pile in the can is plenty. work your way down from the top and then pull it out while still running. Done. No mess.