nowing the plant hardiness zone for our gardens can save us a lot of time, money, and heartbreak. If the dictum “right plant, right place” is true, then we should strive to understand our gardens as a place–defined in part by weather patterns, rising and falling temperatures, longitude and latitude. Every plant hardiness zone will have its idiosyncrasies of elevation, precipitation, and microclimates, but the USDA’s Plant Hardiness Map
remains an essential tool for growers. Since 1960, the USDA has made its data on regional temperatures available as a map divided into 13 major zones for growing based on the average minimum winter temperature. A difference of ten degrees divides each zone, with subsets of five degrees for growers requiring more exactitude.
Visit the USDA’s website here
to find your personal growing zone. When we enter the zip code for the Hudson Valley Seed Company, for example, we discover that we are located in Zone 6a with an average annual minimum temperature ranging of -10 to -5 degrees F. What does this tell us? Well, for one, we can expect tender annuals to eventually succumb to frost in our region. But aside from that, it allows us to shop wisely when we’re selecting perennial vegetables, herbs, and flowers–and to look for varieties that can withstand up to -10 degrees F. We can also use our zone to determine whether a crop might be a good candidate for overwintering (read more about overwintering here
and shop row cover here
). Also of interest from these maps is that they can teach us about the relative climates in our geographic area. For example, in the higher-elevation areas surrounding our homebase in Accord, New York, we find that the zones decrease quickly, through 5b to 5a (with annual lows between -20 and -15 degrees F), while a quick trip into Manhattan sends us to the relatively balmy zone 7b (where it never drops below +5 to +10 degrees F)!
On the subject of frost, another important tool in a gardener’s tool chest is knowing when to expect the last frost for spring sowing and the first frost marking the end of the growing season. To calculate the average first and last frost dates for your garden, try this site
from The National Gardening Association. Use your first and last frost dates to organize your schedule of sowings, or consult one of our universal Planting Guide Posters
To get even more “granular” with the help of a local expert, consult your county cooperative extension. The extension system is a long-standing partnership between the USDA and land grant universities to provide the general public with sound agricultural and gardening advice based on current research. Staffed with paid and volunteer experts and Master Gardeners, cooperative extensions will usually provide a contact for growing advice. Try this site
for finding your local extension, or get in touch with a Master Gardener through this handy website
provided by the American Horticultural Society. These resources will enhance your growing expertise, allowing you to find the "right plant" for the "right place" in your garden.