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CUES: Center for Urban Ecology and Sustainability

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CUES Walkabout

a collaborative project with The Bell Museum of Natural History and The Minnesota Landscape Arboretum)

Welcome to the
Compost Display at the
Minnesota Landscape Arboretum

Composting is an excellent way to recycle your yardwaste at home. Leaves or grass clippings taken to a yardwaste site are plant nutrients lost from that vegetation. By composting, you re-use those nutrients and make your home landscape a bit more self sustaining. Copies of Minnesota Extension Service publications on composting are in the Andersen Horticultural Library in the Snyder Building. There you'll also find information on how to order copies of your own.

Designs for Composters

Three Bin Composter

Our demonstration composter has three bins. The pile on the right is the newest. It's composed of tree leaves, garden debris, and grass clippings. The pile in the middle is composting. no fresh yardwaster has been added since it was moved into the middle bin, ensuring complete degreadation of its contents.

The bin on the left contains finished compost. Go ahead, pick some up and sniff it. It has an earthy fragrance. Use it as a soil amendment or a mulch. You can compost leaves, grass clippings, weeds before they set seed, spoiled fruits and vegetables, vegetable peelings, carrot tops. Avoid adding diseased plants, pet feces, eggs, grease or fat, bones, meat or cheeses.

Bag Composter

If you don't have space for compost bins, you can do bag composting.

In the fall, mow the leaves on the lawn to chop them into smaller pieces. Collect the leaves in large plastic bags. Add a scoop of soil to each bag and dampen the leaves, if necessary. Set the bags in a shady, out of the way place.

In the spring, turn the bags to mix the contents. Do this once or twice during the summer. By fall, or certainly by the next spring, you'll have compost ready to use in your garden.

Common Composting Concerns

My compost pile doesn't heat up!

There are several reasons: If the pile is less than 3' x 3' it might not have enough mass to heat up. Optimal size range for compost pile is 3' x 3' to 5' x 5'.

Or, you might need to add more nitrogen to the raw materials you're composting. When building a compost pile, strive for a mix of 50% brown to 50% green raw materials.

Brown materials are leaves, straw, dead plants. Green materials are grass clippings, seedless weeds, carrot tops, etc. which supply nitrogen, a food source for microbes and bacteria that breakdown the materials in the compost pile. In a pinch, add high nitrogen fertilizer to the brown material, such as inexpensive lawn fertilizer - without weed killer.

Or, the pile might lack air needed by the hungry microbes. Turn compost occasionally to incorporate not only fresh air, but to turn the outer layer of the compost pile, into the center.

Heavy rains also create a sodden compost pile and drive out the air by filling up pore space. During rainy weather, cover the compost pile to deflect excess moisture.

Will a compost pile stink?

Compost piles develop a foul odor when the contents becomes compacted. A thick layer of grass clippings packs down and stinks. A compost pile that is too wet will also become malodorous.

Avoid odor problems by turning the piles regularly to incorporate fresh air into the composting materials.

Why can't I use diseased plants and weeds with seeds?

To kill the disease organisms and weed seeds, compost has to get quite hot, 140-180 degrees. Most home compost piles don't get hot enough. Send seed-heavy weeds and diseased plants to a commercial drop site where they'll be composted at higher temperatures.

Will a compost pile attract mice and rats?

A compost pile turned regularly heats to internal temperatures in excess of 100 degrees, making it unattractive to rodents.

Avoid eggs, meats, bones, fats/grease and animal feces in the compost pile. These may attract rodents.

How will I know the compost is done?
Compost is "done" when the original components are no longer recognizable. The composted material has turned into a soil-like material with an earthy fragrance.

For Further Information

The University of Minnesota Extension Service has the following bulletins on composting:

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Last modified on March 06, 2013