If you’ve been dutifully adding vegetables and food waste to your compost pile or rotating bin, it may be time for the next step: using it in your garden.
How do you know when compost is ready?
Homegrown NH Host Emma Erler, lead horticulturist at Kirkwood Gardens, says most gardeners practice “cold composting,” allowing kitchen scraps and yard waste to gradually decompose into organic matter over time. She says it can take between six months and two years to fully break down.
To be usable, compost should be dark and crumbly, damp but not soggy, and you should not be able to recognize the original composted materials.
In your pile, you will probably find the bottom third will be ready to use. Just rake off the top so it can continue decomposing in an active pile.
How to use your compost
Erler says compost helps to increase nutrient levels and improves soil structure, drainage, and the water-retaining capacity of your garden soil.
- On established flower beds, work in approximately 1 inch of compost over the entire bed, keeping it away from plant or tree stems. For new beds, till or turn 2 to 3 inches of compost before planting. Keep in mind that cold compost will likely contain weed seeds.
For vegetable beds, add up to 3 inches of compost and till or incorporate into the soil with a broadfork in spring or fall.
Erler notes that compost should not be considered your primary source of nutrients in the vegetable garden.
The nutrients in compost will mostly be in organic form and therefore unavailable for immediate plant uptake. They will become available slowly over time as they are broken down by microbes.
Screen compost for existing lawns and spread a thin layer (one-quarter to a half-inch) after thatching or coring, and before seeding.
For a new lawn, compost can be used to improve soil by tilling 2-3 inches of compost into the topsoil before seeding.
- Trees and shrubs benefit from compost, and 1-2 inches can be applied over the entire root zone to the drip edge, avoiding the trunk to prevent rot.
- For use as erosion control on exposed slopes or erosion prone areas, spread coarse compost (materials left after sifting) as 2-4 inch deep mulch.
- You can add compost to potting mix for houseplants or seed starting. The microorganisms in compost may help suppress plant diseases such as “damping off.” Aim for about 30% compost by volume.
See you in the garden!
If you have a gardening question for Homegrown NH, email or send a voice memo to HomegrownNH@NHPR.org.
Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
