The majority of vegetables that are usually grown in flats are grown for about 4 weeks before they are set out into the garden. The other thing to consider is germination time which is usually in the 4 days to two week range. Usually the catalog or package will have the information about germination time. Add the germination time to the time in flats. Then subtract that from the date you want to plant it outside. It's better to have the plant a little young when set out rather than old enough that the roots have hit the bottom and sides too much and have started stunting the plant. A book which has very detailed information about the time in flats is How to Grow More Vegetables than you ever thought possible on less land than you can imagine by John Jeavons. The 5th edition is the latest. Try to get it as it has about 25% more info than the fourth edition. Check the packages or the Square Foot Gardening book to see whether a vegetable gets planted before, on, or after the frost free date, and by how many weeks in either direction. Sharon gordonse@one.net