Soil thermometer use
You will need a good quality soil thermometer (usually about 6 to 8 inches long--measuring temperatures from low 40's to upper 80's). Be careful not to confuse a soil thermometer with a compost thermometer--they are NOT interchangeable. It is suggested you take 2 measurements of the seed bed in which you intend to plant. The first should be the temperature 1 to 2 inches down--this is slightly below where your seeds will be , but will provide the soil warmth needed for them to sprout well. Then, since direct seeded plants need warmth in the root zone, take another measurement 4 to 6 inches down, which will indicate if there is enough ground heat for growth.. You will find appropriate temperatures for both germination and growing out in many sources--some seed catalogs, the back of some seed packets, or in a reference such as The New Seed-Starters Handbook by Nancy Bubel. Keep in mind that direct sun can raise temperatures rapidly in the top 2 inches, but in the root zone it may still be very cool. You might want to be equipped with some cloches, floating row cover, or at a minimum, some cardboard boxes to cover newly seeded areas if the weather turns wet and cold. Good luck, and thank you for using Ask an Expert.