Q1. Can I place cardboard on my garden during the winter?
Q2. I have many harvested pepper plants and leaves from the garden. Can I put these on the garden over the winter?
Thank you for contacting the Toronto Master Gardeners. The main purpose of mulching your garden during the winter is to help stabilize the temperature and prevent unnecessary freezing and thawing that can damage and heave plant roots and bulbs. A thick layer of snow does this well but is not something we can count on in Toronto winters any longer! Cardboard (and newspaper) are sometimes used to suppress weeds. Weed seeds will be dormant in winter so these methods are most effective in spring, summer and fall. There is some discussion in the horticultural field regarding the use of newspaper and cardboard and you can read more here. These products are typically covered by some kind of organic mulch to prevent the cardboard or newspaper blowing away and to aid in their decomposition .
Organic mulches such as harvested plant debris, leaves, wood chips, straw and compost are all appropriate things to add to your garden for winter. A layer of 2-4 inches is ideal to insulate the ground and add nutrients to the soil as they decompose over time. Your pepper plants and leaves can be used for this purpose. If you are able to chop them into smaller pieces (e.g., with a mulching lawnmower) this will hasten decomposition and decrease matting of leaves, but is not essential. Diseased or pest infested plant material should be put in the City yard waste and not in compost or on garden beds.
This article from the University of Nebraska Extension provides a general overview of winter mulching and may be of interest to you Winter Mulching. In addition, the Toronto Master Gardeners is hosting an online “Garden Chat” on Wednesday October 27th at noon about Fall Garden Clean-up. Free registration is available here.
Best of luck!