How should I overwinter empty containers used for vegetables and annuals. I have covered the surface with plastic garbage bags in the past, thinking this protects the soil over the winter. Then just left them on the ground on my patio. I thought I would add a layer of mulched leaves and then wrap with plastic this year. Please advise as to best practices. Thanks!
Thanks for contacting us with your question.
You didn’t mention what kind of pots you have. If they are ceramic or clay or another material that would crack then yes, you’d need to cover them with something – preferably a tarp that is reusable from year to year rather than plastic that you throw in the garbage after each season. If the pots are sturdy/flexible plastic or fibreglass or some other material you would still use a tarp to prevent wear and tear from freezing and thawing.
It’s great that you are trying to re-use your soil rather than dumping it in the garbage. However, it’s recommended that you first make sure that the soil is clean and that the plants that were growing in it did not have bacterial, fungal or viral diseases.
This involves sterilizing the soil – see the link below for a few methods to do this. You can then refresh the soil with compost – about one third compost to two thirds potting soil – and also a handful of sharp sand or chicken grit (used to feed chickens) or perlite for drainage. Then add shredded (undiseased) leaves to the top to mulch.
You can do this for each individual pot, or you can dump all the soil into a bin such as an old garbage or recycling or compost (green) bin for the winter, sterilize in spring and then mix in the appropriate amount of compost. Refill your pots. This would also help to aerate the soil. Then add shredded leaves to each individual pot after you’ve potted up your plants – this will keep the roots shaded and cool and help prevent moisture evaporation.
Doing it the second way would allow you to stack the pots, especially if you are short on space. It also allows you to clean out the pots with water and a bit of dish soap to sterilize them before you use them the following year.
A third option is to spread the soil in your garden beds or lawn and use fresh soil and compost the following year – again, after you’ve sterilized the pots.
Note that the link below suggests removing large roots and dead plants – if the plants were not diseased you can chop them up a bit and spread them in your garden to decay naturally. Otherwise, put them out with municipal yard waste – this is generally heat-treated to kill off any pathogens.
Finally, if you used the soil to grow members of the Solanaceae (nightshade) family such as tomatoes, peppers or potatoes, we suggest re-using this for your annuals or other vegetables such as legumes, as a form of crop-rotation, because: (a) tomatoes are heavy feeders and the soil will be more depleted than with other plants; and (b) nightshades are more likely than other plants to carry diseases that can be passed on through the soil to other members of the nightshade family.
In that case, you may want to separate these nightshade soils into a different bin.