Weeds in a Compost Pile

It's best to avoid reintroducing weeds into the garden through compost.

Many gardeners will quickly balk at the idea of putting weeds in a compost pile, and for good reason. By placing weeds in the compost, you run the risk of re-establishing them in the garden when your compost is deployed. Most weeds can be safely composted if they're pulled before they have a chance to go to seed. Taking heed of a few basic precautions for weeds in a compost pile can help a gardener avoid a maintenance headache.

Composting Basics

Broadly speaking, compost is the process by which organic matter -- both from plants and animals -- is decomposed into humus, a constituent of new soil. Many schools of thought exist on compost, and sometimes agriculturalists disagree on how to best maintain a healthy compost pile. Nonetheless, there is common agreement that all organic matter will compost, though some things take longer than others. Weeds will break down in a compost pile, too, but can present some problems.

Rules for Composting Weeds

As a rule of thumb, it is not a good idea to compost weeds. Compost piles will not kill weeds, and some especially noxious weeds are able to resprout from their roots or branches. Less aggressive weeds can be composted safely, but it's sometimes wise to let them sit out in the sun a couple of days after pulling them so that they may dry out and begin to decompose before being exposed to a potentially fertile compost heap. Also, always try to compost weeds before they go to seed, as seeds are difficult to break down in a compost pile. Adding weeds that have gone to seed into the compost will increase the likelihood that they'll be reintroduced into the garden.

Pernicious Weeds

Especially problematic weeds like quackgrasses, blackberries, witch grasses and morning glories should be kept out of the compost pile altogether. While some weeds will not resprout in a compost pile unless they've gone to seed, especially persistent weeds are able to grow from even the smallest root pieces. For this reason, they should generally be kept out of the compost to avoid having them overrun the compost pile and to prevent reintroduction into the garden.

Composting Against Weeds

Curiously, composting can be an effective method for getting rid of weeds. Agriculturalists at the Ohio State University Extension recommend using leaf mulch as a means to suppress weeds in the garden and to help fertilize crops. This also helps to maintain an appropriate balance in the compost pile by not overloading it with carbon matter like leaves, paper and straw. Simply spread fallen leaves around plants and they'll slowly break down into an effective fertilizer for the nearby plants.

References

• Ohio State University Extension; Composting at Home; Frederick Michel, et al.
• Grist; Umbra on Composting Weeds; Umbra Fisk; 2006
• Enjoy Gardening; Composting Weeds; Jim Hole; 2005
• VegWeb: What Not to Compost; 2009
• Home Composting Made Easy; How to Compost Leaves, Weeds and Garden Debris; C. Forrest McDowell, et al.; 2007

Resources

• How to Compost; Make Use of Your Fall Leaves; Kristin Black