Saturday, December 29, 2012

Resolve to compost in the new year

Compost helps your garden by providing nutrition to your soil.

The Roanoke Times | File 2010

Compost helps your garden by providing nutrition to your soil.

Karen Hager is The Roanoke Times' gardening columnist. Her column appears twice monthly in Extra.

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About Karen

Karen Hager lives in Blacksburg with her garden-loving family: a husband and son. She learned her skills by trial and error, and encourages all gardeners to do the same. You can reach her at

No matter what type of gardening you engage in, and no matter how large or small your garden, every gardener should make a resolution to compost in the new year.

Compost is partially decomposed organic matter, commonly made up of plants or plant-based foods, and sometimes the manures of plant-eating animals. Because compost is made mainly from plants, it usually contains the growth elements that plants need in roughly the proportion that they're needed.

Compost helps your garden in many ways by providing nutrition to your soil, improving the structure of your soil, and increasing your soil's ability to retain water. Using compost also can help to prevent some plant diseases.

Because most compost has a pH level at which most plants thrive, adding compost also will help to stabilize the pH of your soil. And it encourages microorganisms by serving as a food source for soil-dwelling creatures.

When compost is fully decomposed, it's known as humus. Humus contains humic acid, which makes essential minerals present in the soil more accessible by plants. Humus also stimulates seed germination and plant growth, so fewer fertilizers are needed to get good yields.

As a practical matter, composting is a way to turn waste products from kitchens, gardens and yards into a valuable resource. Why throw items in the trash when you can recycle them into garden gold instead?

How to compost

Composting is nature's method of recycling. Bacteria and other soil-dwelling organisms break down organic matter on a continuous basis. If you set out to make compost, you're just speeding up the process.

Nearly all organic materials can be made into compost, but some things are better to put into your compost pile than others. Being choosy means that you'll have compost quicker and your compost will be better balanced.

Composting occurs fastest when you use a balance of about 30 parts of carbon to 1 part of nitrogen, by weight. Most people don't remember which materials supply which elements, so it's helpful to think in terms of 30 parts of "brown" materials to 1 part of "green" materials.

Brown materials that are good sources of carbon include the dried-out stems, leaves and stalks of plants. Straw, hay, cornstalks, pea vines and bean vines are all good brown materials to use.

Autumn leaves tend to mat together and prevent air from entering the pile, so don't make these the main ingredient in your brown layers. It's better to shred and add leaves directly to garden soil.

Pine needles decompose slowly and are very acidic, so keep them out of your compost pile, and instead use these materials as mulches for acid-loving plants.

Green materials that are sources of nitrogen include almost any fresh or slightly wilted plant material. Grass clippings and kitchen scraps are obvious candidates, but nonpoisonous weeds and healthy plant residues from the garden also can be used, as long as they haven't gone to seed.

You should not compost diseased plants or weeds that have gone to seed, or add grass clippings from lawns that have been treated with herbicide. Don't add coal ash to your compost pile, as coal ashes are toxic to plants, and be aware that using wood ashes will raise the pH level of your pile. It's usually better to keep wood ash out of the compost pile and apply it directly to beds to adjust pH.

Don't use the manures of cats and dogs in your compost pile. Manures of meat-eating animals may contain disease or parasites that are harmful to people.

Hot vs. cold

All composting gives off some heat, which is the byproduct of bacteria digesting organic material. Different bacteria thrive in different temperatures.

When the heat generated by bacteria is between 70 degrees and 90 degrees, this is called a "cold" pile.

When conditions exist for bacteria to thrive and raise temperatures as high as 160 degrees, this is known as a "hot" pile.

You get a cold or hot pile depending on how you build and maintain your compost pile. Hot and cold piles are built the same way, but the recipe for a hot pile is more exact.

A hot compost pile is the best way to make compost quickly. The high temperature will kill many of the pathogenic organisms and weed seeds present. A hot pile works best if it's made up all at once and then allowed to compost completely without further additions of material. More maintenance will be required to assure that the pile's temperature stays high.

Cold compost piles take longer, don't destroy pathogens or weed seeds, but can be built over a period of time. If you are recycling a small, steady stream of organic matter, you'll likely be doing it in a cold pile.

Once you build a cold pile, sit back and let nature go to work. Keep an eye on the moisture level and add some water if needed. After a few months, turn the pile, bringing material from the middle to the edges. It will take a year or more to get finished compost, but it requires very little effort. You can also use it sooner as a topdressing or mulch, or mix it into your soil in fall.

Ideally, all ingredients in a compost pile should be mixed together, but layering will work fine, as long as the layers aren't too thick. Looser materials can be piled thicker without risking compaction and loss of air.

If all of this sounds too complicated, you always can fall back on the lazy method of composting. Throw everything in a pile, taking care of which items to include and not to include, and let nature take its course.

Eventually, everything breaks down, even if you take no further action. And what results will help to make your garden healthier and happier.

Visit my blog at for more tips on composting.

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