Composting the Remains of a Garden Season

September begins the busiest composting season. Through the autumn months, one of our compost bins fills to overflowing with discarded plant material from every part of the garden, while the contents of other bins are harvested for autumn mulching of garden beds.

It begins when the first chilly nights finish off already-worn-out potted annuals. These plants, their green leaves and subtle stems still relatively high in nitrogen, are dumped into an empty compost bin, their tightly woven root-balls chopped up with a sharp spade. This layer is then mixed with an equally thick layer of high carbon material, such as straw or the woody stems of spent perennials, and then a thin layer of finished compost from the adjacent bin is mixed in to kick-start decomposition.

It is an inaugural event. Over the next several weeks the pile grows with uprooted potato vines, the baked skins of winter squash and apple peels from a weekend soup marathon, mildew-covered summer squash plants, shriveled sweet pea vines, thick-stemmed sunflower stalks, the rest of the potted plants, overlooked cucumbers and zucchinis the size of footballs, worn-out pole bean plants, retired tomato vines, and a legion of weeds. These materials are all relatively high in nitrogen, so we layer them with relatively high carbon materials such as straw or shredded autumn leaves, once they become available.

Everything gets chopped with the spade as much as possible. Vegetable scraps from the kitchen get tossed in, buried deeply in the pile to discourage the local wildlife from rummaging through the pile. The growing pile is soaked with water at the end of each day’s work.

Then in late September or early October, we make several trips to the goat farm for loads of composted goat manure. While most of these nannyberries get stockpiled under tarps for the winter (they are almost impossible to acquire in spring when they are actually needed), some are spread thinly over the surface of the compost pile to increase the host of composting bacteria.

So the pile grows through October. Layers of well mixed garden debris, both green and brown, thin layers of composted manure, more garden debris, and so on. If I have time to harvest a bucket or two of seaweed from the high tide line, an excellent source of nitrogen, it gets mixed into the pile, and the stream of compostables from the kitchen never ends. On cold October mornings, steam rises from the heart of the pile where bacteria are still hard at work.

We don’t bother to turn this autumn compost pile when its core cools. At some point the fire goes out and the pile acquires a cap of ice and snow. Come the spring thaw, we will turn the pile into one of the empty bins, moving the material on the edges to the center, and watch the needle on the compost thermometer inch upward as the pile heats up.

If I wanted to keep those thermophilic bacteria working through winter in the center of the pile, a minimum size for the bin would be 5 feet by 5 feet by 5 feet (ours are a more standard 4 feet by 4 feet by 4feet), and here in northern New England, I would still need to insulate the perimeter of the bin with straw bales or other suitable material, more work than I care to undertake.

We are careful not to toss dandelions, quackgrass, and other perennial weeds into the compost pile, nor any weedy plant that has gone to seed. The roots and stolons of perennial weeds, as well as many weed seeds, can survive the hottest compost pile temperatures to show up in the garden wherever the compost is spread.

On the other hand, we do not hesitate to compost the spent nasturtiums, calendulas, Shirley poppies, and other self-sowing annuals that we like to see pop up in the garden as volunteers year after year. By the time they are tossed on the pile, they’ve sown so many seeds through the garden that a few more surviving the composting process will not be noticed.

Finished compost can be used as an autumn mulch around garden trees, shrubs, and perennials.

Finished compost can be used as an autumn mulch around garden trees, shrubs, and perennials.

As the autumn compost bins fills with the remains of summer, the bins that contain finished compost empty as their contents are screened, then spread around the strawberry plants, highbush blueberry shrubs, and raspberry primocanes. If there is a surplus of finished compost, the grape vine and peach tree are next in line, followed by the garden’s trees and shrubs. When the compost gives out, we continue mulching with nannyberries until every tree and shrub is surrounded by a think layer of dark crumbly mulch that will be quickly incorporated into the soil come spring. This is the only fertilizer that the woody plants in Marjorie’s Garden ever need.

Finished compost should be screened to eliminate any materials, such as corn cobs, that have not had time to decompose.

Finished compost should be screened to eliminate any materials, such as corn cobs, that have not had time to decompose.

Screening finished compost is always necessary. Corn cobs, orange rinds, and sunflower stems take forever to decompose, so anything too large to pass through a 1-inch wire mesh screen is recycled through the growing compost pile. A coconut half-shell spent three years in our compost piles before finally ending up as a bird feeder on the back porch.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: http://www.facebook.com/pages/The-New-England-Gardeners-Year/187285218055676.)