Choose the Best Regional Version with our Frost Date Maps
To select the best regional version for your local climate, you should know your average frost free dates. Remember, average means that half of the the time your last frost date will fall before this date–and half of the time it will fall AFTER this date. It is not the last possible date of frost. If you are not sure of your local frost free dates, you can use our frost date map. This map has been compiled from average first and last frost date maps from the Internet Accuracy project (scroll down to see original maps).
Frost is also effected by the proximity of water, wind shelter, altitude, and microclimates. A stone wall or nearby pavement can create a warm bubble, and a perennially shady spot (like a conifer grove) could be in a colder zone than the rest of your garden.
These are the approximate areas recommended for each of our different versions. Extremes of altitude, temperature or humidity may require some adjustments of planting dates.