Organic gardening experts are constantly telling us to improve our soils with organic matter, but what kind? Fully decayed organic matter — compost — is, in the words of one* of my favorite gardening books, “the creme de la creme, the piece de resistance, the best in show, the big rock candy mountain of organic matter.” Not convinced yet?
Why it’s SO Great
- Compost improves soil structure, no matter what kind of soil it is. Got clay? It’ll loosen it, letting water drawn from it and oxygen get down to the roots. And in sandy soils, the ability to hold moisture is increased by compost.
- Compost contains nutrients.
- Compost also feeds micro-organisms, thus increasing plants’ ability to USE the nutrients.
- Compost attracts earthworms, which further enrich the soil and improve its structure.
- Using homemade compost reduces the need for products you have to buy, especially the synthetic stuff.
- Unlike those fast-acting synthetics that end up polluting our waters, compost releases its nutrients slowly.
Buying it vs. Making It Yourself
Of course you can buy Leafgro, an excellent leaf-based product available everywhere, or one of the generic bags of compost available in stores. Or you can make it yourself. That way it’s free, it requires no trips to the store, and it avoids adding all that nutritious waste to the local landfill. (I’ve seen estimates that 10 to 30 percent of our landfills are filled with yard waste!)
What to Compost — and Not To
- Leaves (chopped for faster results) and other green yard waste.
- Kitchen scraps, except for animal parts, dairy or oil, which can attract rodents.
- Shredded newspaper and cardboard.
- Don’t use possible contaminants like pet waste, diseased plant parts, or anything sprayed with pesticides or herbicides.
- To avoid having your plants seed all over the garden, remove the seedheads before composting the rest of the plant.
- Don’t use woody plant matter over 1/2 inch thick without chopping it up first.
- The more diversity of composting materials, the better. So get creative.
Composting by Piling it On
The cheapest technique (actually free) is to simply put organic materials in a pile, turn and water them occasionally to keep them aerated and moist, and wait while the invisible microorganisms do their job and compost happens. Making a depression in the top of the pile catches rainwater.
To speed the process, chop or shred the contents first by running over them with a bagged lawnmower or putting them through a chipper-shredder of some kind. I once tried a cheap shredder that used a Weedwacker-type plastic filament to shred my leaves, but found that every tiny stick and acorn broke the filament, so the process was extremely slow-going. On the other hand, I know gardeners who report excellent results with their weedwackers, even the homemade kind.
One wrote to tell me, “I have a leaf shredder that cost less than $100. It’s basically a weedwacker in a can and fits over a garbage can to catch the shredded leaves. I’ve never had a problem with the filament breaking — and you can always get heavier filaments at the hardware store that are almost guaranteed not to break.”
Even easier is what I do with the huge amount of fallen leaves on my property — dump them in a pile and do nothing but add my green garden waste to the pile. Then by fall the pile has settled and I use my handy pitch fork to pile it higher, making room for the next batch of fallen leaves. The resulting product is honestly more like leafmold than fully decomposed compost, but it still works as a good soil amendment or as mulch in my woodland garden.
Composting with Homemade Containers
- If you don’t have huge quantities of leaves to compost, some sources suggest just putting them in black plastic garbage bags to slowly break down. If you chop or shred the leaves first and wet thoroughly before closing the bag, punch holes in the sides, tie the top, and check back in 12 to 18 months, you might have leafmold (partially decomposed leaves) but not actual compost. And Ed thinks even that prediction may be overly optimistic.
- Another cheap and easy container is a plastic or metal trash can with the bottom cut out and holes punched in the sides and lid for air circulation. To ensure good drainage, place it on top of wood chips or bricks.
- Create a homemade container using concrete blocks, bricks, or wood. It should be 3-sided, a 3 to 5-feet square, and no more than 5 feet high. Also, wooden pallets can be nailed or wired together at the corners to create a compost container. A round container can be easily constructed using wire fencing. Whichever method you use, it’s best to have two or three side-by-side containers so you can move the contents from one to the other to aerate.
- People with very limited space can use 4-foot-tall wire fencing, cut to any size and filled with leaves. Whether the compost has completely decomposed or not, it can be dug into the garden in spring as a soil amendment.
Another gardener wrote to tell me he plants seedlings right in the top of the leaf bin. He makes a slight depression and adds a quart of so of soil, then plants vegetable seedlings. “The thing to remember is that these leaf beds do need to be kept watered.” Well, whoda thunk?
Containers to Buy
You can buy plastic compost bins that are either stationary or made to be tumbled using a lever. The tumbling type is meant to be filled all at once, so you need some space to save the materials until they’re ready to be added, then turned. Also, don’t fill the tumbler too full or there won’t have room for the ingredients to mix as you’re turning. And as always, shredding ingredients first makes compost faster. Tumblers, because they’re closed, are excellent for urban situations where rats are to be discouraged.
Hot vs. Cold Composting
Unlike the cold composting methods described above, which often take a year or more, some gardeners prefer speeding up the process in a method called hot composting. It produces results much faster — as fast as three months is possible! — and kills more weed seeds than the colder methods, though not all. Temperatures inside the pile reach as high as 170 F.
How to Maximize Results from Cold Composting
Experienced cold composters often aim for the perfect combination of 8 parts brown materials, 2 parts green, and 1 part soil. The finished compost from such a cold pile will release nutrients slowly and is preferred for long-term fertility of the soil. (Compost from the hot process might better be used on one-season plants.)
How to do Hot Composting:
- You may have read that the ideal ratio of brown (carbon-containing) materials to green (nitrogen-containing) is 30 to 1 but don’t get hung up on that number because it refers to the absolute amount of carbon or nitrogen, not the quantity of matter you throw in the bin. Best I can tell, real composters recommend either equal parts brown and green bulk ingredient or two parts brown to one part green. (Who knew there were so many conflicting opinions?) Brown ingredients are dry leaves, newspaper, and straw. Green are yard waste like grass clippings, and most kitchen scraps. If there’s not enough green, the decomposition takes longer. If there’s too much green, your compost bin will smell bad.
- Hot piles are best created all at once, not gradually.
- Some sources recommend layering the ingredients, alternating green and brown, and watering between layers, while others say that layering isn’t necessary.
- Add to the mix a little soil, by itself or with sod attached, or some manure. No commercial “compost starters” is needed. Some composters add liquid fertilizer when they water for faster results.
- Chop or shred the ingredients first.
- Serious hot-composters (at least those in a hurry) turn their ingredients daily, if possible, by moving them to a different bin or pile. This ensures good aeration. The less frequently you turn, the longer it’ll take to get results.
- Keep the contents moist by hosing them down during the turning process. Compost with the right consistency feels like a wrung-out sponge.
- A compost thermometer tells you what’s going on and is a big help.
What to do with it
When your compost product is finally crumbly and black or dark brown, it’s time to use it in the garden. Possible uses include:
- For new planting areas spread 1-2 inches on the surface, then mix it into the soil before planting.
- For vegetables, work a 1-inch layer into the soil at the beginning of the season, and follow by adding a bit more (no more than a half-inch layer) before each new planting throughout the season.
- Apply 1-2 inches on top of the soil and just leave it there to work itself into the soil gradually (letting earthworms do most of the work). To make the garden look more finished and to help prevent weeds, apply a thin layer of actual mulch on top. (Wind-borne weed seeds will germinate when they land on compost but not on mulches.)
- Add to the planting holes of new plants, up to one-third, and mix well with the garden soil.
- Apply 2-3 inches over the root system of troubled plants
How much do you need?
To cover an area with anything, including compost, here’s the formula:
Take the square footage of area to be covered by the desired thickness of the application, then divide by 324 to yield the amount in cubic yards. For example, a 200-square-foot area covered with 2 inches is 200 x 2 = 400 divided by 324 = 1.23 cubic yards.
More Great Info on Line
- Ed Bruske’s Composting Video, in 15 short clips, is here on MonkeySee.com.
- EPA’s Guide to Composting.
- Florida’s On-Line Composting Center.
- The Great Compost Tea Debate between two published experts in the field. First up is Jeff Gillman, next the counterargument by Jeff Lowenfels, and then a brief rebuttal and lots of great comments by readers.
- Master Composter programs are sprouting up all over the country, training people to teaching composting in their communities.
- Compost Bin Blog
- Compost Guide
- Composting with worms, called vermicomposting, is right here on this site.