Questions About Composting

Answers to common composting questions

From Composting in the Home Garden, Illinois Extension

​​​​​​​Are oak leaves too acidic to be used for compost?

No, oak leaves in compost will not create an acidic soil. However, you need to be careful when applying walnut leaves because they contain a growth inhibitor to which some plants are sensitive. Walnut leaves must be thoroughly composted before applied to the garden.

Are there any plants that I should not use compost around?

The pH of compost is slightly basic (or alkaline), thus avoid adding compost to acid loving plants such as azaleas or hollies.

Can I add sawdust to the compost pile?

Yes, sawdust can be added to the compost pile. However, compost has a very high amount of carbon, so if you add sawdust, add nitrogen (such as a cup of 10-10-10 fertilizer per 25 square feet). To be safe, avoid adding sawdust from lumber treated with CCA (chromated copper arsenic).

How do I know when compost is ready?

Compost is ready to use when it is dark brown, crumbly and has an earthy odor. Compost is ready when it is fluffy, and should not be powdery. The original materials that were put into the compost pile should not be recognizable, except for small pieces of stems.

Can I add weeds to the compost pile?

Weeds will not be a problem for compost piles that heat up properly. However, if the pile does not reach high enough temperatures, weed seeds may not be destroyed and could pose a future problem.

Is outdoor composting possible during the winter?

Weather can have both positive and negative impacts on outdoor composting systems. Extremely cold temperatures slow down rather than completely halt the composting process. Download the infosheet for tips on increasing success with winter composting systems.

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