The USDA has split the United States into hardiness zones for planting. These zones indicate the average annual minimum temperatures for each region. There are 11 hardiness zones, from zone 1 in Alaska to zone 11 in Honolulu, Hawaii. Gardening using these zones as a guide for which plants are best suited for your area and for the appropriate time of the year to plant will help your garden be as healthy, beautiful and productive as it can be.
Obtain a copy of the USDA Hardiness Zone Map--USDA Miscellaneous Publication No. 1475--either by contacting the USDA or by going to its website. The U.S. National Arboretum has an interactive Web version of this map that allows users to click on the area of the nation they live in to pull up a map with a closer view of that section of the country. These maps will allow you to find out the zone in which you live.
Check with the American Horticultural Society's Heat Zone Map to learn what heat zone you are in. This will also help when choosing what plants to purchase, as it is important to know if a plant can tolerate the heat in the area as well as the freezing temperatures.
Go to a few local nurseries to see what kinds of plants they have for sale. Most nurseries will only carry plants they know will be adapted to the area they are selling in. Read the information tags that accompany the plants to make sure they are recommended for your hardiness zone. Ask questions of the person who is working at the nursery--many of these people have a lot of information about local plants and will know which plants are well suited and which are not.
Shop online for plants that you desire for your garden. Most of these stores will provide information about each plant including the hardiness zone it is most suited for. Choose plants that are recommended for your zone. Some plants can be purchased if they are rated for one zone higher or lower than recommended, but there is a greater risk of failure in these plants and extra care may be needed to protect them from harsh environmental elements.
Check websites ending in .edu for more information about particular plants you may be interested in. These are university and college websites and most have agricultural departments or agricultural extensions that are dedicated to helping people in their communities with garden questions. If you have interest in a certain type of plant and need to know if it will be suited to your area, this is a good place to go.
Plant your plants only at the recommended times for your zone. On most seed packets, there is an indication of the time of year the seed should be planted based on what zone you are in--be sure to check before planting seeds outdoors.