From our blog, a discussion that gets a bit into the weeds about odds and frost date ranges.
Margaret Roach and Johnny’s offer seed-starting calculators. Enter your frost date, and it calculates when seeds should be started indoors, transplanted, or directly sown outdoors. NOTE: Use these calculators as a rough guide. In the spring, I use two sets of frost dates: a riskier one for cold weather crops that can handle a bit of frost and a more conservative one for warm weather crops. Tomatoes, for example, not only can’t handle a frost, but they’re also generally not happy at temperatures under 60 degrees F.
Winter sowing is a method of sowing seeds outdoors when it’s still cold in containers such as milk jugs. Susan Mulvihill has a nice video on the technique and also points interested growers to wintersown.org.