The Alchemy Behind Black Gold:  The Practice of Composting

Bryan Fischer, Horticulturist, Gardens on Spring Creek

Last week we examined composting as a concept. This week’s article will shift from concept to application. 

Broadly speaking, compost piles are fed three types of inputs: (1) carbon-rich “brown”, like dried leaves, straw, and other small, dried plant materials (twigs thinner than a pencil are OK), (2) nitrogen-rich “green” materials, like fresh grass clippings, kitchen scraps, and seed-free annual weeds and (3) water. Don’t incorporate items such as bones, meats, oils, fats or greases, as these can quickly attract pests. If something doesn’t belong in your garden (like a perennial weed, weed with seeds on it, or garden plant infected with a pathogen) don’t incorporate it into your compost pile. Many of these “baddies” can survive home composting and revel in the opportunity to proliferate in a cushy garden setting later.  

For the purposes of home gardening, “lasagna” style composing is often most practical. Not only does it reduce the measurement required to keep the pile composting effectively, but it can also be done passively with no turning required. To try this, start with a layer of brown materials on the bottom of the pile about four inches thick. Add green material (gradually is fine) until it forms a layer four inches thick, then alternate back to brown. Be sure to keep your rings of green material smaller than your rings of brown material so that pests don’t have easy access to the food scraps in the pile. Expect unturned piles to take up to 12 months to finish their first compost batches; turning the pile will shorten this timeframe somewhat.

While one can fuss about achieving the ideal ratio of green to brown, I just eyeball the pile.  If it appears dry or isn’t composting as weeks go by, add more green materials or water. If it appears slimy or smells stinky, add more brown materials, like leaves. The consistency of a wrung-out sponge is said to be a good indicator of the ideal moisture content of a pile. 

Such compost can be spread prior to planting or seeding of a garden. Ideally, this would be 90+ days before most crops are to be harvested (like tomatoes, beans, etc.) and 120+ days before root crops (like carrots) are to be harvested to minimize chances of a pathogen from the compost surviving on the crop at the time of harvest. Once spread (1-2 inches deep is typically plenty), either till it in as a soil amendment or cover it with mulch. Tilling compost is generally best for vegetable production, with mulching preferred for landscape applications. However, natives and xeric perennials do not require, nor do they appreciate compost. 

I approach compost as I try to do many things in life: less is more. While a light compost addition will typically benefit the garden, one that is too heavy will quickly harm it with excess nutrients and salts, leading to plant stress and leaf burn. After all, gardening is a marathon, not a sprint, even if spring would suggest otherwise. With any luck, you’ll have many more seasons to practice perfecting your “black-gold” operation.