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Does the prospect of free fertilizer and soil conditioner interest you? Then now is the time to take advantage of nature’s annual gift to gardeners: autumn leaves!

The days of curbside burning of autumn leaves are thankfully over. Communities have realized the hazards of smoke pollution and many have banned curbside burning of leaf piles. But besides the pollution issue, burning leaves is a waste of a valuable resource. Autumn leaves are a wonderful organic supplement to garden and shrub beds, preventing unwanted weeds from sprouting while protecting surface roots from winter chill. And as the leaves break down, they add the benefit of adding nutrients to the soil and carbon-rich matter which aerates and conditions the soil to facilitate root growth.

Use leaves to mulch over-winter vegetable beds and shrubs

Now that summer vegetable beds have been harvested, gardeners look to ways of covering any plots of bare soil. Bare soil invites erosion from winter rains, and weeds of every variety quickly move in to take advantage of exposed soil.

Adding mulch to bare soil will prevent soil erosion and control weeds. If you have ‘over-winter’ crops in the garden, it is even more important to mulch to keep the soil surface from freezing in cold snaps and to avoid frost damage to the ‘shoulders’ of root crops. If carrots, beets and other roots are damaged by frost, the rot starts in the damaged areas and spreads to the rest of the roots.

Leaves are ideal as winter mulch because they are light and fluffy, which adds insulation value. Think of a down sleeping bag. Heavier mulches compress and become soggy, providing less warmth. Any kind of leaves are fine, including big leaf maple, oak and arbutus. The only exception is black walnut leaves, as some plants (e.g., tomatoes) are sensitive to the compounds in the leaves. There are other alternative mulches, such as straw, but these mulches cost money and do not offer the equivalent value of leaves. Straw may also harbor seeds which may take root in your beds. Leaves are hard to beat for being a free and weed-free, balanced fertilizer.

In autumn, add a layer of leaves around all plants in the garden. For closely planted crops, such as leeks and greens, scrunch up fistfuls of leaves and stick them in between the plants. This should be several inches thick. For the cabbage family, leafy greens and leeks, pile up leaves as deeply as possible between plants.

Bare beds can be covered with a generous layer of leaves. We blanket our beds with 6” or more as our supply lasts. To prevent the leaves from blowing away with the next strong wind, we have used two methods. The simplest method is to drape a light net (we use the strawberry netting from our summer strawberry beds) and weight down the corners with rocks. If you don’t have any spare netting, another method is to sprinkle garden soil over the leaves. You want to add enough soil to hold the leaves in place but not so much as to compress them into a mat. We use a hoe for this, and chop it into the soil, pulling a bit a soil with each stroke up and onto the surface of the leaves. This only takes a few minutes and very little effort.

Save some leaves for the compost

Over winter, most home composters gradually lose their balance of nitrogen and carbon. Kitchen scraps, high in nitrogen, are added regularly all through the winter. But carbon-based materials are less plentiful in winter. When the compost gets out of balance, the composting process slows down as the materials settle, losing aeration, until the compost becomes cool and soggy. (See our article How to fix a soggy compost pile.) This is where your stored leaves come in handy.

Leaves are an easy available source of carbon for your compost. If you set a sack of leaves next to the composter, simply grab a handful and sprinkle it into the composter as you add kitchen scraps. Give the composter a spin if it’s a tumbler-style composter. By adding leaves gradually, you’ll avoid having them clump and mat together which slows down their decomposition. If you want to add a lot of leaves to lighten a soggy compost pile, then turn them in with a spade or rotate the composter so the leaves don’t mat together.

Once our garden beds are well mulched, we store all the leaves we can round up during autumn in any container available. An old garbage can is ideal, but you can also use empty feed or grain sacks. The woven-poly types of sack are best since they are very sturdy and breathe a bit. Your local feed or farm supply store may have extras available for free. We save any sacks we can, and fold them neatly in a tote until the fall.

Be sure to set stored bags of leaves where they won’t get wet. We store our full sacks under the eaves of the garden shed. If the leaves get wet they will compress and mat together, and lose insulation value. They are still worth saving, however, and adding to your garden beds.

Leave some leaves at the source

It is nature’s design that leaves fall where they do. They offer the parent tree the same benefits that we gardeners are hoping to transfer into our vegetable beds and shrubs. When gathering leaves, keep the needs of the parent tree in mind by leaving some leaves on the ground where they fall.

Gathering leaves in autumn is a great family activity, since even the youngest children can participate. This is a good opportunity to teach the children about the nature of soil and the value of building rich soil for growing productive plants. Some day they may use this knowledge to enrich their own gardens!