There are 11 planting zones on the USDA Plant Hardiness Map in the contiguous United States and southern Canada. The regions are defined by a 10-degree Fahrenheit difference in the average annual minimum temperature in, https://apps.apple.com/us/app/lily-plant-identification/id1570145257 know all abot plants. The higher the numbers, the warmer the temperatures for gardening in those areas. The zones are further broken down into an "a" section and a "b" section, representing 5-degree Fahrenheit differences (for greater precision), with "a" being colder than "b."
Why Do We Have These Zones?
It is standard practice for seed dealers and nurseries to label their products according to their USDA Plant Hardiness Zones. These are the planting zones in which you are most likely to be successful at growing those particular plants. As such, these "zone" designations serve as guides.
Enthusiasts of horticulture plan their gardens carefully. Part of that planning means understanding the USDA planting zones. An important part of the plant-selection process when thumbing through garden catalogs is targeting shrubs, perennials, etc. that are cold-hardy enough to survive a winter where you live.
Growing plants not suited to your region's climate is sometimes possible, but it is not recommended for beginners. Those experienced in gardening, however, often make use of "microclimates." A microclimate is a location on a property where the climate differs from the average climate on that property.
For example, a location against a house's south-facing wall will usually be warmer than other spots in that yard. An experienced gardener could take advantage of this fact by growing a plant there that normally would be a bit too tender for the region.