Overcrowded desks stacked with seeds and seed catalogs are a sign of the season. Whether you are still perusing catalogs and making selections, or your mail box is already filling up with seed packets, making a seed-sowing schedule—whether you are planning a vegetable, herb, or flower garden—allows you organize all the seed packets you have purchased and sow them at the proper time.

Know Your Frost Dates

Ideally, gardeners order seeds based on when they need to start sowing seed, although if you already have a pile of seed packets on hand, it’s still not too late to make a sowing schedule. The first step in creating a schedule is to determine the last spring frost date in your area. You can get single, hard-and-fast dates from your local Cooperative Extension Service, plus there are various guides on the internet that provide frost dates. Perhaps the best is provided by the NOAA Satellite and Information Service.

NOAA gives frost dates for over 4,000 U.S. cities. Unlike simplified sites, it gives last frost dates for three temperatures—28°, 32°, and 36°F—with three levels of probability for each temperature. That allows you to pick a date when there is a 90 percent chance temperatures will drop below a particular temperature, along with a 50 percent chance and a 10 percent chance. The date you choose depends on what crop you are sowing, and also, to some extent, on whether or not you are a gambler.

For example, for cool-weather crops like lettuce, you may be willing to risk cooler temperatures and plant on the date when there is a 50 percent chance temperatures will drop below 32°F. If you are planting warm-weather peppers or eggplant, though, it’s generally best to be safe, not sorry, and wait until you are sure the weather will stay warm.

You can also use the information on the NOAA chart according to how much care you are willing to give your crops. For example, you can plant warm-season crops a little early and plan to protect them with cloches. Or sow cool-season crops extra early and cover them with row covers or plastic tunnels if necessary.

The site also gives dates for first fall frost and total estimated numbers for frost-free days in the growing season.