Why Leaves Are Worth More Than They Look

On a coastal smallholding, the wind rarely lets you keep anything you haven't tied down. Leaves are no exception. Come October, a gale off the sea strips the sycamore and the last of the hawthorn and dumps them against the leeward fence in a dry, rattling drift. Most growers in exposed spots curse this and rake the lot onto the bonfire. That's a mistake. Those leaves are the cheapest soil improver you will ever get your hands on, and the salty air does nothing to spoil them.

Leaf mould is not compost. It is a fungal process rather than a bacterial one, slower and cooler, and what you end up with is a dark, crumbly, almost peat-like material that holds water superbly and feeds the soil gently. On a seaside plot where the ground tends to be thin, sandy or stony, and where summer winds wick moisture out of everything, that water-holding quality is worth its weight in gold. It conditions beds without adding much in the way of nutrients, which makes it perfect for potting mixes and for mulching around plants that resent being overfed.

Which Leaves to Keep and Which to Bother With

Not all leaves are equal, and by the sea you'll have some odd ones blowing in. The general rule is that thin, soft leaves break down fastest.

• Good and quick: sycamore, ash, lime, field maple, birch and most fruit-tree leaves.
• Good but slower: oak, beech and hornbeam. These are acidic and take up to two years, but the resulting mould is superb.
• Avoid: horse chestnut, sweet chestnut and walnut, which are leathery and slow. Also skip anything evergreen — holly, laurel, conifer needles — as these can take three years or more and turn sour.
• Leave alone: any leaf with black spot on roses, or with obvious mildew, and anything that has washed up in the tide line. Seaweed is wonderful stuff, but it belongs in the compost heap, not the leaf bin.

If you garden somewhere the salt spray really bites, you may notice a white crust on leaves blown in from the shore. A quick shake and a light rinse with the hose before they go in the bin sorts it. In practice, rain does most of the work for you.

Building a Wire Bin That Stands Up to the Wind

The classic wire bin is still the best method, and it costs almost nothing. Make a cylinder roughly a metre across from galvanised wire mesh with a 25mm or 50mm grid — small enough to hold the leaves, open enough for air and rain. Line the inside with a couple of stakes driven into the ground so the whole thing doesn't set off across the field in a February storm. On a really exposed site, put it behind a hedge or a shed wall, and consider a second stake on the windward side.

Site it on soil, not on concrete or gravel, so worms and fungi can move in from below. Fill the bin as you collect, treading it down lightly every so often to stop the wind lifting dry leaves straight back out. Water it if the leaves are bone dry when they go in — a bin of dry leaves will sit unchanged for years. Aim for the texture of a wrung-out sponge.

You can run three bins side by side: this year's collection, last year's part-rotted, and finished mould ready to use. If space is tight, a single bin works fine, you just wait.

The Patient Bit — and How to Speed It Up

Leaf mould is a slow business and there's no honest way around it. Expect 12 months for a usable mulch and 18 to 24 months for fine, crumbly mould you can sieve and use in potting compost. The fungi doing the work are happiest in damp, cool, airy conditions, which is exactly what a coastal autumn and winter usually delivers.

A few tricks genuinely help:

• Shred them. Run the mower over a pile on the lawn, or stuff handfuls into a bin and go at them with a strimmer. Shredded leaves rot in half the time.
• Mix in a little nitrogen. A sprinkling of grass clippings between layers, or a handful of blood, fish and bone, gives the fungi a boost without turning the heap into a smelly compost pile.
• Turn once or twice a year. Not essential, but it re-aerates the mass and lets you check moisture.
• Keep it damp, not sodden. Coastal rain is usually enough, but a bin under a dripping roof line can dry out at the top while staying wet underneath.

Don't panic if the bin looks inert for months. The change tends to happen quietly, and one spring you'll push your hand in and find the bottom third has turned to something dark and friable.

Using Leaf Mould in a Seaside Garden

Once it's ready, sieve it if you want the fine stuff and keep the coarser material for mulching. In a salty, free-draining plot it earns its keep in several ways. Fork it into vegetable beds in autumn to bulk up thin soil and improve its ability to hold water through a dry, windy July. Spread a 5cm layer around soft fruit, roses and perennials as a summer mulch; it suppresses weeds and stops the surface panning hard after heavy rain.

For pots, mix roughly one part sieved leaf mould to two parts soil-based compost and one part grit or sharp sand. That gives you a free-draining but moisture-retentive mix that suits bay, rosemary, lavender and other seaside stalwarts far better than a rich, heavy compost. It's also excellent as a seed-sowing mix for anything that doesn't want much feeding.

Salt spray, wind and thin soil make coastal gardening hard work. Leaf mould is one of the few things that asks nothing of you but time, and the leaves are already blowing into your yard. Build the bin, fill it, and let the weather and the fungi do the rest. Two years from now you'll have barrowloads of the best soil conditioner money can't buy — and you'll never burn a leaf again.