This is my second year of vegetable gardening, but first year of intensive in-ground beds gardening. I read that the last frost date for Toronto is May 11-20. I live just north in Thornhill. My question – to confirm, is it still too early to plant seeds/seedlings?
Thanks for your help!
Your information regarding the last frost date – or range of dates – is accurate. The old adage is that planting before the Victoria Day weekend in Ontario is not advised because there may still be a risk of frost, and this is by and large a good rule of thumb for planting many crops, either by seed or seedlings. Planting too early can leave your vegetable seedlings vulnerable to frost damage.
The Ontario Ministry of Agriculture, Food and Rural Affairs provides information on climate zones and planting dates in Ontario, including a map that will help you determine when the last average frost date in your area is. There is also a range of planting dates for various vegetable crops by zone: http://www.omafra.gov.on.ca/english/crops/facts/climzoneveg.htm
If you have started seeds indoors, you will need to “harden off” your seedlings, that is, acclimatize them gently by moving them outdoors in the daytime over a period of a few weeks. Here are some helpful guidelines: http://www.omafra.gov.on.ca/english/crops/gardbk/gh-ch4-1tips.htm
Your seed packages should have specific directions, which provide good guidance. Depending on the vegetable, your packet may say “plant outdoors when all danger of frost has passed” or “when night temperatures are above 10 °C”. Some vegetables like lettuces, spinach and radishes are considered to be “cool weather crops” and seeds can be sown in the garden in early spring, as soon as the ground can be worked, i.e., has thawed.
Vegetable plants purchased at a nursery will typically have been hardened off before they are sold to you, but if you buy them before all danger of frost has passed, you will need to be aware of overnight weather forecasts and make sure to protect them.
You may also find the Toronto Master Gardeners Guide to Organic Vegetable Gardening useful: https://www.torontomastergardeners.ca/gardeningguides/organic-vegetable-gardening-a-toronto-master-gardeners-guide/
Very best of luck with your venture into intensive in-ground vegetable gardening.