The Vegetable Garden

Why is compost special?

Building and maintaining a compost pile is the surest, easiest way to become a better gardener. Not only will you be producing the best possible food for your garden, but by watching leaves, eggshells, orange rinds, and grass clippings become transformed into rich compost filled with earthworms and other soil creatures, you'll be learning what healthy soil is all about.

Compost is a rich and crumbly blend of partially decomposed organic material that does wonderful things for your garden.


Compost improves soil structure. Most gardeners don't start with great soil. Whether yours is hard and compacted, sandy, stony, heavy, or wet, adding compost will improve its texture, water-holding capacity, and fertility. Your soil will gradually become fluffy and brown -- the ideal home for healthy plants.

Compost provides a balanced source of plant nutrients. Even if you are lucky enough to have great soil, you can't expect that soil to remain rich and productive without replenishing the nutrients that are consumed each growing season. No commercial fertilizer, even one that is totally organic, provides the full spectrum of nutrients that you get with compost. The nutrients are available gradually, as your plants need them, over a period of months or years. The microorganisms in the compost will also help your plants absorb nutrients from fertilizers more efficiently.

Compost stimulates beneficial organisms. Compost is teeming with all kinds of microorganisms and soil fauna that help convert soil nutrients into a form that can be readily absorbed by your plants. The microorganisms, enzymes, vitamins and natural antibiotics that are present in compost actually help prevent many soil pathogens from harming your plants. Earthworms, millipedes, and other macro-organisms tunnel through your soil, opening up passageways for air and water to reach your plants' roots.

Compost is garden insurance. Even very experienced gardeners often have soil that is less than perfect. Adding compost moderates pH and fertility problems, so you can concentrate on the pleasures of gardening, not the science of your soil’s chemical composition. Unlike organic or inorganic fertilizers, which need to be applied at the right time and in the right amount, compost can be applied at any time and in any amount. You can't really over-apply it. Plants use exactly what they need, when they need it.

Can a gardener ever have enough compost? It's doubtful. Compost is the perfect thing to spread around when you are creating a new garden, seeding a new lawn area, or planting a new tree. Compost can be sprinkled around plants during the growing season or used as a mulch in your perennial gardens. You can add compost to your flower boxes and deck planters. You can also use it to enrich the potting soil for your indoor plants.

How compost happens

Organic matter is transformed into compost through the work of microorganisms, soil fauna, enzymes and fungi. When making compost, your job is to provide the best possible environment for these beneficial organisms to do their work. If you do so, the decomposition process works very rapidly -- sometimes in as little as two weeks! If you don't provide the optimum environment, decomposition will still happen, but it may take from several months to several years. The trick to making an abundance of compost in a short time is to balance the following four things:

Carbon. Carbon-rich materials are the energy food for microorganisms. You can identify high-carbon plant materials because they are dry, tough, or fibrous, and tan or brown in color. Examples are dry leaves, straw, rotted hay, sawdust, shredded paper, and cornstalks.

Nitrogen. High-nitrogen materials provide the protein-rich components that microorganisms require to grow and multiply. Freshly pulled weeds, fresh grass clippings, over-ripe fruits and vegetables, kitchen scraps and other moist green matter are the sorts of nitrogen-rich materials you'll probably have on hand. Other high-protein organic matter includes kelp meal, seaweed, manure and animal by-products like blood or bone meal.

Water. Moisture is very important for the composting process. But too much moisture will drown the microorganisms, and too little will dehydrate them. A general rule of thumb is to keep the material in your compost pile as moist as a well-wrung sponge. If you need to add water (unchlorinated is best), insert your garden hose into the middle of the pile in several places, or sprinkle the pile with water next time you turn it. Using an enclosed container or covering your pile with a tarp will make it easier to maintain the right moisture level.

Oxygen. To do their work most efficiently, microorganisms require a lot of oxygen. When your pile is first assembled, there will probably be plenty of air between the layers of materials. But as the microorganisms begin to work, they will start consuming oxygen. Unless you turn or in some way aerate your compost pile, they will run out of oxygen and become sluggish.