Garden School:

Garden School:
Teaching this week: Assessing a new garden, and when to say "No" !

Tuesday, 3 March 2015

Leaf Mould: lovely stuff!

I get quite evangelical about both leaf mould and compost, which is hardly surprising considering it's my job... but even now, I am still surprised to find that so many gardeners are fully prepared to spend hours faffing with their compost heaps, but are not interested in making the much smaller effort to make leaf mould.

It does requite a little bit of knowledge, certainly, and a spare corner of the garden,  but once set up, it is hardly any effort at all.

All you have to do, quite literally, is make a lightweight pen to keep them together - in this one, you can see that I have used chickenwire and odd stakes and branches for the corner posts:  my Client and I like to use recycled and natural materials wherever we can.

Generally speaking, it takes nearly two years from start to finish: much slower than compost, but well worth the wait. So you will need to build three pens, filling one pen per year. By the time you are starting to fill the third pen, the first pen should be just about ready for use.

I've put in posts all round to keep the leaf mould away from the outbuilding wall and from the fence, to avoid any damp problems.  This one measures about a yard deep and nearly two yards long, but frankly the size depends more on where you can fit them in, and what materials you have to hand.

Oh, and make a note of that white slab against the fence!

Here we have the new pen, newly filled with leaves in December 2013.

All I do is quite literally rake up the leaves, and tip them in, pressing them well into the corners.

I take care not to include any Horse Chestnut leaves - they take forever to rot - and of course no conifers.

This is mostly Beech and Hornbeam from the hedges, Mulberry from the big tree, Birch, and a lot of Lime from the Lime Walk.

They all go in together, in no particular order, and I make sure they have a good sploosh of water on them after I tip them in. If it's a frosty morning, there's no need to add water, but generally speaking leaf mould pens fail for lack of water more than for any other reason, so add a bucket-full to each layer and you won't go far wrong.

Oh, and - as with your compost heaps -  make sure not to allow a "cone" to form: level off the top, to ensure that water stays inside the pen, and doesn't drain straight out.

Each week, I would find that the heap had sunk down 6" or so, so I could add that week's rakings, and water it well.  At one point I had more leaves than I could fit in this one pen, so I used the one next door for temporary overflow, and made a mental note to make the next set bigger!

Once the leaves stopped falling, I stopped adding, and left the pen alone. For the first month or so I would fling a bucket or two of water over it if I happened to be passing, but that was it.

Here we are in March 2014, it was sinking well, but you can't yet see the top of the white slab.

By June 2014 it had reduced by about half, and the top of slab is just showing.

By December 2014, the slab was halfway visible as the pile continued to shrink.

All this time, there was no stirring, no turning, no adding chemicals, nothing at all except letting it get on with the natural process.

And by January of this year, 2015, it was ready for use.

And here is that pen, opened up, with the top layer of dry stuff scraped off: I don't waste that material, I just add it to this year's pen.

As you can see, lovely stuff! Thick, black, fluffy, lightweight, totally smell-free.

It's worth repeating that this leaf mould material has little "goodness" in it: it's not like compost, which is rich and full of nutrients. The leaves give most of their nutrients back to the tree before they drop, but what we are left with makes wonderful soil conditioner: if the soil is sticky clay, it breaks it up: if the soil is dry and sandy, it helps it to hold water: it lightens a heavy soil, and it thickens up a very poor soil.

Wonderful stuff indeed!

Mostly I mix it 50/50 with home-made compost then use it as mulch on the surface, or for digging in when planting holes are needed. You can also use leaf mould for germinating, as being quite low in nutrients, it won't encourage the seedlings to outgrow themselves before they have formed proper root systems.

So there you have it, leaf mould in just one year: even I am impressed, as I always tell people that it takes two years to make good stuff. I think I had the right balance of a good big pen, the right volume of leaves, ie more than would fill it, and plenty of water.

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