How to build a better garden with compost

This spring, I planted six kale plants in a row down the middle of a raised vegetable bed. In a few weeks, three plants on one side were almost twice as big as the others.

Growing conditions were the same but for one thing — I had dug compost in the soil where the healthier plants grew. Though I added commercial soil for raised beds to the other side, it was the area with my compost — which last year was a heap of banana peels, coffee grounds, weeds and tired soil dumped out of plant pots — where the magic happened.

Composting, and adding the resulting organic matter to soil, is the easiest and most effective way to build a better garden. Compost improves soils. Mixing it into clay soil lightens it, improving drainage. Mixing it with sandy soil adds humus, increasing water retention. Plants grow better.

A thick layer of compost mulch helps prevent weeds, conserves moisture and, over time, improves soil quality by adding organic matter.

Composting helps the environment, too. According to the state Pollution Control Agency, 12% of Minnesota garbage is food waste, and up to 18% is yard waste. Why not keep some of this material on your property and help your garden grow?

Creating compost isn't complicated or expensive. The University of Minnesota Extension Service has a variety of do-it-yourself compost bin designs (extension.umn.edu/how-manage-soil-and-nutrients-home-gardens/composting-home-gardens) that use chicken wire or hardware cloth and cement blocks.

If you prefer to buy a bin, check your county or city website. Hennepin County sells bins at www.hennepin.us/composting. Washington and Ramsey counties have bins available at recycleminnesota.org/work/compost-bins-rain-barrels/.

Suspended barrel bins that are turned with a crank are expensive and rarely large enough to produce much compost. I've had good success with a black plastic compost bin that sits on patio blocks. With a removable top and a sliding door at the base, it keeps big pests like raccoons out of the pile and provides easy access to finished compost at the bottom.

Before setting up a bin, it's wise to check city ordinances to see if there are rules on compost bin sizes and locations. An easily accessible spot in sun to partial sun is best, because heat speeds compost pile decomposition.

Much has been written about the proper proportion of brown (generally dry) and green materials (wetter) for compost bins. Dried leaves and grass, straw and small twigs are brown ingredients; green stuff includes kitchen waste like fruit and vegetable scraps, coffee grounds and plant trimmings. The key is to have a mix of both to speed decay. Too much brown stuff will make the pile too dry, and it will just sit there. Too much green stuff risks making the compost too wet, leading to an anaerobic pile that reeks and doesn't decompose well.

Compost piles should be moist, not sodden. If a pile seems too dry, add green stuff and a bit of water. If a pile is too wet, stir it with a shovel. If you don't have enough brown ingredients, adding shredded black-and-white newsprint can help. Newspaper ink is soy-based and poses no risk to the garden.

If you catch your lawn clippings, you can add those, too, but make sure they are scattered and don't form a thick mat in your bin. Don't bother with commercial "compost starter" mixes. A handful of herbicide-free lawn fertilizer, mixed into the pile, will get microbes moving, and the occasional shovel of soil helps move things along, too.

Never add pet feces, meat, cheese or bones. Anything with fat or oil shouldn't be included in a home compost pile, and weeds with seeds or parts of diseased plants shouldn't be added, either.

It's up to you to determine how aggressively to manage your compost. A new pile started in the spring, kept moist and regularly turned, will yield compost by fall. If you're a lazy composter like me, it can take up to a year to get good compost. I add material to my bin all summer, stir it with a shovel now and then, and top it off with root-clogged soil from the pots I empty in the fall. By the following May, I usually have about three-quarters finished compost in my bin.

This year I had enough compost to mix into and mulch the raised beds where I planted tomatoes. Not only did the tomatoes grow well, but the compost stayed fluffy and loose on the surface for weeks and I didn't have to water as much as usual. That this material came out of my own kitchen and yard, enriching my garden instead of going into a garbage can, really was magical.

Mary Jane Smetanka is a Minneapolis freelance writer and a Hennepin County Master Gardener.