Composting Q and A

By National Gardening Association Editors

Starting a Compost Pile

Question: When is the best time to start a compost pile and what are the best things to put in the pile?

Answer: Any time is the right time to start a compost pile! Springtime is great, because you'll have lots of weeds and vegetable matter to add. Although there are all sorts of "formulas" for the perfect compost pile, all you really need to understand is that you should aim for a balance of nitrogen and carbon sources. Nitrogen sources include anything fresh and green -- fresh grass clippings, freshly pulled weeds -- also kitchen vegetable scraps, and manures. Carbon sources tend to be brown -- straw or old hay, for example, or dried leaves. The smaller the pieces of material are, the quicker they will decompose, so, if possible, chop up waste. You can even run the lawnmower over a pile of fall leaves, to break them up. Then, simply begin layering your "greens" with your "browns". Occasionally, throw in a shovelful of dirt to introduce some microorganisms and earthworms. Keep the material moist but not soggy. That's it!

Critters in Compost

Question: I started a compost bin early last spring. When I recently added the compost to my garden, I noticed that it contained a lot of brown beetles and slugs. I saw no ordinary earthworms, though. Are these critters supposed to be in the compost and do they help the process of composting?

Answer: A healthy compost pile should be teeming with creatures of all kinds, ranging in size from microscopic to inches long. You've probably uncovered some potworms and scarab beetles. These are normal discoveries in a compost bin. Earthworms are sensitive to heat and generally stay out of compost bins, preferring to live in the cool, moist soil. Don't worry about most of the creatures you see, as they won't hurt your garden or growing plants. Their preference is to feed on and break down organic debris. Slugs are another matter, though. They will feast on your plants, so keep an eye out for them and remove them.

Foul-Smelling Compost Pile

Question: My compost bin has a slight foul odor to it. What is wrong? Should I go ahead and spread it anyway?

Answer: Foul-smelling compost is a sign of too much moisture. Try turning the compost to incorporate some air and help excess moisture evaporate. The pile will heat up when it has the right moisture content, and you can keep things cooking by moving the cooler material on the sides into the center of the pile. Your compost will be ready to use when it's brown, crumbly, and has unrecognizable bits of organic matter. It should smell like clean soil. If you can still identify roots or leaves, the compost needs more time.

Adding Compost to a Perennial Garden

Question: I have a compost bin and am eagerly looking forward to "feeding" my garden soil with nutrients. However, the garden is almost all perennials. How do I incorporate compost without disturbing the plants? I've read that you spread out 4 inches of compost and till it in 8-10 inches deep, but that doesn't seem to make sense unless you're starting with an empty garden. What's the best way?

Answer: You can spread a thin (1" - 2") layer of finished compost over the soil around your perennials. As it continues to decompose it will provide nutrients to the roots of your plants. Perennial beds usually need to be dug and divided every 3-4 years when the plants become overcrowded. You can use this opportunity to incorporate additional organic matter into the bed prior to replanting your perennials.

Speeding Decomposition

Question: My husband and I started a compost pile this past fall. The weather has been cold, and we've had a lot of rain. The compost is not doing anything. We've probably turned it once a month or so, and have been adding shredded leaves, household vegetable garbage, yard clippings, etc. It's obvious we won't have any nice compost ready for this spring's gardening, but when will we? Should we have waited to begin it in warmer weather? Is there anything we can add to speed-up the process?

Answer: A compost pile cooks best if you turn it frequently. Cold weather and an abundance of rain will definately slow the process. Next winter try placing a tarp over the top of the pile to keep excess rain out or use a covered compost bin. For now you can help speed things up by completely mixing the pile up and adding some nitrogen-rich fresh grass clippings. As the weather warms and dries out, the pile will begin to heat up. Turn the pile once a week or so, moving the center of the pile to the edges and the edges of the pile to the inside, where it's nice and warm. Remember to add a shovelful of soil every once in a while to incorporate some beneficial organisms and good bacteria. Compost happens. Good, fast compost takes a little extra effort!

Planting Directly in Compost

Question: I was told by one person that it was OK to plant directly in compost. Since then, I have been told by someone else that it is not a good idea. Who is correct?

Answer: If you've ever had a monster squash plant growing out of your compost pile, you'll know that it is possible to plant right in compost. However, although compost is a fantastic soil amendment, it's usually lacking in some nutrients or minerals that are found in soil, which could show up as deficiencies in your plants. As a general rule, mix some compost into your existing garden soil before planting. That way, the plants' roots won't be tempted to stay within the bounds of the nutrient-rich compost, but will travel into the surrounding soil, where they'll be better able to withstand drought and other adverse weather conditions. Also, as the compost continues to decompose, its volume is reduced. So it's best to mix it into soil to prevent perennial plants from sinking down.

Compost Quantity

Question: I am planning on preparing my garden soil by tilling and adding compost. Is there a danger of adding too much compost? Is there a suggested quantity?

Answer: Organic matter, such as compost, is so helpful to the soil that you can safely spread a 4"-5" layer over the top of the soil and till it in without worrying about overdoing it. After planting, add a 2"-3" layer of compost as a mulch. At the end of the season you can dig or till it into the soil. Since compost breaks down over time, you can add a similar amount year after year to your garden.

Compost vs. Mulch

Question: Is there a difference between compost and mulch?

Answer: The terms are often used interchangeably. However, compost is decomposed organic matter that can be incorporated into the soil to improve its fertility, structure, drainage (in clay soils) and water-holding capacity (in sandy soils). Mulch usually refers to different types of organic matter that can be layered on top of the soil to moderate soil temperatures, reduce weed germination, and retain soil moisture. Compost can be used as a mulch, as can bark chips, straw, dried leaves, etc. Of course, all of these materials can also be used to make compost. Another way of looking at it, is that compost is generally in a more decomposed state than mulch.

Materials to Compost

Question: Can I add coffee and tea grinds to my compost pile?

Answer: You can add almost any vegetable-based matter to your compost pile, including garden debris, raw vegetable and fruit trimmings, used coffee ground, tea leaves, stale bread, etc. The important things to keep out of the compost pile are bones, meat and fish scraps, cheese, oil, and fat. These things will break down in a compost pile, but you might be inviting rodents and insect pests, which can be difficult to eradicate. Also, avoid adding pet feces, because they can harbor disease organisms.

Sawdust in Compost Pile

Question: Would adding sawdust to my compost pile be beneficial or detrimental? We have access to lots of it.

Answer: Sawdust has an extremely high ratio of carbon to nitrogen. That doesn't mean that it won't decompose, but you would need to mix it with a great deal of material high in nitrogen to try and balance it out, or use it sparingly as your carbon source. And, you'd probably have to keep adding more nitrogen to keep the process going. Materials high in nitrogen include grass clippings, manure and fresh green garden trimmings or kitchen scraps. Sawdust makes a good mulch for garden paths because it is slow to break down. It might be better to use it to keep weeds down in garden paths.

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