When is soil generally considered “workable” in Toronto?
Thank you for writing to the Toronto Master Gardeners with your question. I am presuming that you are asking about the growing season.
According to Agriculture and Agri-Food Canada, http://www.agr.gc.ca/eng/science-and-innovation/agricultural-practices/climate-change-and-agriculture/future-outlook/climate-change-scenarios/length-of-growing-season-in-ontario/?id=1363033977515, the growing season is measured in days starting from the estimated seeding date (10 days after the average daily temperature is above 5°C) until fall frost (when the minimum daily temperature is 0°C) or until October 31st – whichever comes first. This is the same time period used to calculate effective growing degree days.
Furthermore, the Coupled Global Climate Model (CGCM 3.1) predicts a 1 to 2 degree Celsius increase in monthly average temperatures from now to 2039, resulting in earlier crop seeding dates, and later fall frost dates.
According to the NOAA, the National Centres for Environmental Information, on average, the frost-free growing season starts about May 9 and ends about Oct 6, totalling 150 days.
Good luck with your planting.