Backyard Composting Class Recap – Greenspring Horticultural Center

On a Saturday in August, several of us attended the Backyard Composting class at the Greenspring Horticultural Center. The class was led by Pamela Smith, Community Horticulture Supervisor and Volunteer Coordinator for Greenspring, as well as the Clark House and White Gardens, properties owned by Fairfax County.

Pam described composting as the natural breakdown of organic waste into a nutrient-rich, soil-like material that, while not a fertilizer, is highly valued by gardeners and farmers. She emphasized the importance of maintaining a 3:1 ratio (by volume) of carbon-rich "brown" materials to nitrogen-rich "green" materials for optimal decomposition.

Examples of compostable materials:

• Nitrogen (greens): kitchen scraps, green plant clippings, green lawn clippings

• Carbon (browns): dry leaves, conifer needles, woodchips, sawdust, newspaper (excluding glossy pages), and dampened cardboard

  
  

Pam highlighted the importance of water, oxygen, and bacteria in the composting process. Compost can be made in piles, bins, or trenches, but the pile must stay moist and be turned regularly to introduce oxygen, which speeds decomposition and helps generate heat. Ideal compost pile temperatures range from 120–150°F, which can help kill weed seeds and plant pathogens. Adding a little soil can introduce beneficial bacteria, and breaking materials into smaller pieces accelerates the process.

Pam also discussed materials to avoid in composting: meat, bones, dairy, grease, charcoal, carnivore waste, glossy magazines, and plants with milky sap. Citrus peels and avocado pits break down slowly and should be added sparingly, if at all.

To deter pests, enclosed composters are recommended. Another option is vermicomposting, which uses red wiggler worms to break down waste—a different but effective method that also results in rich organic material.

The class concluded with a tour of Greenspring’s composting area, a large-scale setup using multiple open bins with wooden dividers to manage the various stages of decomposition for their garden waste. Recommended Reading: Stu Campbell Let It Rot Charles Dowding Compost: Transform Waste Into New Life