Thursday, 16 September 2021

What is the difference between compost, organic matter, and leaf mold?

This is a question from a recent Training Day Student: they asked me to clarify the differences between compost, multi-purpose compost, leaf mold, farmyard manure, potting compost, John Innes, organic matter, etc  - what were they, what was the difference between them, and did we use them for different things?

This is an excellent question!

It's one of those things that every professional gardener knows, as a matter of course, and it's easy to forget that we were all new to it, once. 

So here we go! What do we have, under the general heading of "compost"?

1) Compost - home-made

2) Compost - multi-purpose

3) Farmyard manure

4) Organic matter

5) Manure from someone's muck heap

6) John Innes products

7) Leaf mold

Let's look at each of those in turn - grab yourselves a cup of tea, folks, this might be a long post!

1) Compost - home-made. This is what we make in our own gardens,  from our own weeds, cut-down herbaceous material, kitchen vegetable scraps and so on, which rot down into "compost". It is free to make, and it is fantastically "eco", because we are keeping all the nutrients within our own garden, which is a good thing for many, many reasons. It teaches us about the true meaning of recycling, it reminds us of the circular nature of gardening, and it teaches us patience - it takes as long as it takes, and there is no point trying to rush it.

Use for: potting on cuttings, digging into beds and borders, using as a mulch.

Pros: free to make, on hand when we need it (because it's already in our gardens!), rich with nutrients.

Cons: takes time, is messy - and compost pens are rarely pretty, plus they take up space in our gardens.

2) Compost - multi-purpose. This is the stuff we buy in plastic bags from the garden centres. It used to be made mostly from peat, mixed with rotted plant material,  but now we know that Using Peat Is Bad, so it's mostly plant-based by-products such as coir, bark, coconut husks, and so on with - allegedly - added fertiliser.  It's mass-produced, it often contains contaminants such as glass, stones, plastic etc, which vexes me, and I have written about this at length. The worst thing about shop-bought compost is that if you let it dry out, it is very difficult to re-wet it: you have to tip it into a tray, add water, and physically push the water into the dusty compost, using the same action as when you "rub up a crumble". And if you don't know what that means, I've described it in detail, here

Use for: seedlings, potting on cuttings, potted plants. 

Pros: cheap to buy, easy to transport (it comes in bags), fairly clean to use.

Cons: goes dusty if allowed to dry out, only contains enough nutrients for 6 weeks (read the pack! It says so!), is often contaminated, is of variable quality, and uses a lot of carbon with packing, transporting, storage etc.

3) Farmyard manure. This is now available in bags, to buy, from garden centres, which used to make me laugh like a drain when I first saw it. Yes! People are buying small bags of cow poo! *laughs* Anyone who has ever walked past a farm will know what a huge volume of cow poo is produced in the UK, great steaming heaps of it, so it strikes me as amusing that townies are buying it in dainty little 50litre bags.  However, if your garden soil is lacking in nutrients, or in "body", then adding farmyard manure is the best thing you can do, and at least by buying it, you are supporting the farming industry.

Use for:  digging into beds and borders, using as a mulch.

Pros: neatly packaged, clean to transport, good rich stuff. Properly speaking, it should be regulated, so it should contain known amounts of nutrients, and should not contain more than an acceptable level of chemicals, drugs, etc (ie all the treatments given to the cows, in their normal farmed lives).

Cons: again, packaging, transporting: all of which is a high carbon cost.

4) Organic matter: this is the posh name for farmyard manure. For squeamish townies who don't like the idea of putting cow poo on their gardens. Poor souls.

5) Manure from someone's muck heap. Anyone with a horse or two will gladly give the stuff away for free, because horses, like cows, are basically poo-machines: you put grass (hay/feed etc) in one end, and get poo out of the other. The trick is to get what is known as "well-rotted manure". Fresh horse poo is too "hot" to use on plants: it generates heat as it rots, and literally burns the plants. But very old horse poo, which has been badly stored, or has become water logged, is horrible stinky stuff, and will not doe your roses much good. "Well rotted" manure is a homogenous mass, which does not smell of anything in particular, and is not unpleasant to the touch. If you can see individual "clods" of poo, then it is not well rotted. If it stinks, it is not well rotted. If it is slimy and heavy, it is not well rotted. If someone invites you to help yourself to their muck heap, ask them which is the oldest one, and head there.

Use for:  digging into beds and borders, using as a mulch. 

Pros: free! Should be lovely rich stuff, full of nutrients.

Cons: you normally have to shovel and bag it up yourself, so it's hard work, and can make a mess of your car.  Also, it may well contain drugs/chemicals from anything given to the horses, ie worming treatments, other medication etc. Another good reason for heading for the oldest part of the muck heap, in the hopes that any chemicals will have degraded.

6) John Innes products: ah, the holy grail of gardeners. Loam based products, finely graded and tested for nutrient value, and selected for various uses, ie seed compost, potting compost etc. Loam, by the way, is the Ultimate Soil. It's friable, holds water well, full of nutrients and minerals, is lovely to handle, etc etc etc. 

Use for: seedlings, potting on cuttings, plants in pots: there is a different grade for most requirements.

Pros: all of the above.

Cons: expensive!

7) Leaf mold. A bit of a soap-box of mine... I am always writing about it, I've even written an eBook about it!  (How to Make Compost and Leaf Mold - does what it says on the cover...) Briefly, you just rake up all your fallen tree leaves in autumn, and let them rot themselves down into a wonderful lightweight, fluffy, non-smelly product which you cannot buy... no, no-one sells it, I can't think why, and as soon as I move house and get a bigger garden, I am going into production, believe me! Leaf mold does not contain much in the way of nutrients, but has a lot of minerals, and is a truly fantastic soil conditioner. 

Use for: seedlings and potting on cuttings, if mixed 50/50 with compost:  digging into beds and borders, using as a mulch. 

Pros: free! Easy to make! Takes an annoying waste product - dead leaves - and turns it into something wonderful!

Cons: takes time - 2 years minimum. But patience is a virtue....

So there you go, a quick run-down of the main types of "compost", their differences and their uses. 

And to make it even easier for you, here's a handy table!





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