by Catherine Haug, November 2, 2011
Using leaves in your compost or as mulch is an excellent way to return nutrients to the soil. But it’s not as simple as just piling them on. The Composter Connection has a great article on composing leaves: Using Autumn’s Bounty: Leaf Compost, Leaf Mulch, Leaf Mold, by Bill Kohlhaase.
You can read the entire article online, but here’s a few notes I made as I read the article.
Leaves do far more good in your compost, than in a landfill, so rake with joy and next spring your garden will thank you for it. But it’s not just a matter of piling them on. While a pile will produce leaf mold (see below), they will not decompose properly without mixing with a source of nitrogen in your compost pile.
Nutrition of leaves:
- “Pound for pound, the leaves of most tress contain twice the mineral content of manure.” But leaves of different trees provide different minerals.
- They dramatically improve aeration and drainage in your soil.
- They encourage growth of valuable microbes in the soil.
- Leaves have the most nutritional value when they have first fallen, so it’s important to rake and shred early.
Leaf Mulch, Leaf Mold, Leaf Compost
What you intend to make with your leaves will determine the process you use.
- Leaf mulch protects perennials and shrubbery, and improves the soil’s water holding capabilities;
- Leaf mold helps with soil drainage problems, by improving the crumb and friability of the soil;
- Leaf compost provides vital nutrients to enrich your soil; making compost is enhanced by addition of ‘green manure’ which provides nitrogen to help with decomposition of the leaves.
The Process
Raking
- Freshly fallen leaves contain the most nitrogen and minerals, and their cells are still pliable and friendly to decomposition.
- Start raking as soon as they start falling from your trees; it takes several weeks for all to drop.
See 12 Rules of Raking (2) for more.
Shredding
- Shredding is essential for making compost, and beneficial if making leaf mold.
- If you don’t have a shredder, mow over a pile of leaves several times, to break them up.
- Leaves break down slowly – may be 3 or more years if they are not shredded & mixed with green manure or other nitrogen source.
- Tip: mow lawn and leaves (to shred them) together, then rake them together.
Leaf mulch
- Mulch can be applied under trees, shrubs and plantings to protect and insulate the soil.
- Loft is important – the trapped air increases the insulation ability.
- Leaves generally increase the acidity of soil. Test mulched soil in the spring and add wood ash, lime or other alkaline substances to raise the pH if needed (6).
- Finely shredded leaves tend to work themselves into the soil and encourage moisture absorption, without inhibiting the warming of the soil.
- Whole, or poorly-shredded leaves should be pulled back in spring so soil can warm.
- Store excess leaves for use during growing season as mulch; this is best if they have been shredded. The stored leaves are making leaf mold.
- Mulching directly into your lawn has advantages and disadvantages. See When Leaves Turn Into Litter for more.
Leaf mold
- Leaf mold is made much the same way as compost, but without the addition of nitrogen.
- Simply pile the shredded leaves in a bin or cage, keep them moist, and leave it to time. Turning occasionally is helpful but not necessary.
- If the leaves are finely shredded, and you regularly turn the pile, you’ll have leaf mold in 12 months. Otherwise, the process can take up to 3 years (5).
- When left in contact with the earth, the leaves interact with microbes in the soil to form leaf mold.
- Making leaf mold (or compost) in raised beds greatly improves the volume of your soil.
- Leaf mold absorbs five times its weight in water, making it an excellent addition to hard and clay soils.
- Add leftover leaf mold to your compost pile.
See Paghat’s Garden: Leaf Mold (4) and Garden Web: How do you make leaf mold? (5) for lots more.
Leaf compost
Making leaf compost is not much different from making any other compost.
- Use a bin, cage or tumbler to contain the shredded leaves;
- Provide regular moisture;
- Pay attention to the carbon:nitrogen (C:N) balance. Leaves are 60 parts carbon to 1 part nitrogen, another nitrogen source should be added, such as green manure such as lawn clippings, or animal manure.
- You can also just add your shredded leaves to your household compost or humanure.
- To avoid matting of a mostly-leaves pile, frequent turning is a must. [However, if adding leaves to humanure or household compost, frequent turning is not recommended – see my earlier article What Makes your Compost Tick? for more.]
- Maintaining correct C:N balance is not always easy. For one thing, manure has more weight per volume, less of it than what appears to be 20 percent by volume will give a correct balance.
- Layering green and brown helps for eyeballing balance.
- When you have a lot of leaves, don’t be tempted to make your piles too large: they are harder to turn and contain.
- The classic “three bin” method (7) of composting is a great way to keep large amounts of leaves organized and progressing through the decay cycle.
- Leaves may make your compost/soil too acidic, so be sure to test the pH and add alkalizing agents as necessary (see Changing the pH of your soil (6) for more). Pine, fir, spruce, oak and maple leaves are the most acidic.
- Interesting efficient method: Rake unshredded leaves directly over the remains of your vegetable garden at the end of the season, then rototill the entire plot to break up the leaves and greens and mix them with the soil. Add manure or green manure to the mix. A second rototilling in a week or so is recommended, to further break down leaves
For more information
- Using Autumn’s Bounty: Leaf Compost, Leaf Mulch, Leaf Mold, by Bill Kohlhaase.
- Mother Earth News: 12 Rules of Raking
- When Leaves Turn Into Litter
- Paghat’s Garden: Leaf Mold
- Garden Web: How do you make leaf mold?
- Savvy Gardener: Changing the pH of your soil
- Chiot’s Run: Three-Bin Compost System
See also my earlier posts on composting: