Using USDA Plant Hardiness Zones and Ecoregion Maps to Find Your Growing Region

Learn how these two essential tools help you understand your local environment and choose the right plants for success.

By Garret Merkley · Explainer · Jun 7, 2026

Branched from Selecting Local Native Plants for Your Specific Ecoregion

Quick take

USDA Plant Hardiness Zones indicate the average annual extreme minimum winter temperature, crucial for plant survival.
Ecoregion Maps describe broader ecological characteristics like climate, geology, and native vegetation.
Using both together provides a comprehensive understanding of your local growing conditions beyond just winter cold.
These tools are vital for selecting plants that will thrive, especially when choosing native species.

To successfully grow plants, you need to understand the specific conditions of your location. The USDA Plant Hardiness Zone Map and Ecoregion Maps are two fundamental tools that provide distinct but complementary information, helping you pinpoint your growing region and make informed decisions about what plants will thrive there.

How USDA Plant Hardiness Zones Work

The USDA Plant Hardiness Zone Map divides North America into 13 zones based on the average annual extreme minimum winter temperature. Each zone represents a 10-degree Fahrenheit range, further split into 'a' and 'b' subzones (e.g., Zone 6a, 6b) representing 5-degree differences. This map is primarily a guide for perennial plants, indicating which ones are most likely to survive the winter cold in a particular area.

For example, if a plant is rated for Zone 7, it means it can generally tolerate winter temperatures down to 0 to 10°F. If you live in Zone 6, that plant might struggle or die during a typical winter. It's important to remember that these are average minimums, and unusual cold snaps or microclimates in your yard can still affect plant survival.

How Ecoregion Maps Work

Ecoregion maps offer a much broader, more holistic view of an area than hardiness zones alone. They classify regions based on their dominant ecosystems, taking into account interacting factors such as climate (beyond just winter minimums), geology, physiography (landforms), vegetation, hydrology (water systems), and soils. Various organizations, like the EPA, have developed different ecoregion frameworks, but they all aim to delineate areas with similar ecological characteristics.

For instance, two areas might be in the same USDA Hardiness Zone, but if one is a sandy coastal plain and the other is a rocky mountain slope, their ecoregions would be vastly different, indicating very different native plant communities, soil types, and rainfall patterns.

Why Both Tools Matter for Your Garden

While hardiness zones tell you if a plant can survive winter, ecoregions tell you if a plant will truly thrive year-round, considering all the other environmental factors. Pairing these two tools provides a powerful understanding of your local environment. For example, a plant might be hardy in your zone, but if it requires consistently moist, acidic soil and your ecoregion is characterized by dry, alkaline conditions, it will struggle. Using both ensures you're selecting plants that are adapted to your specific climate, soil, and moisture conditions, leading to healthier plants, less maintenance, and greater success, particularly when aiming to plant native species.

Finding Your Zones and Ecoregions

**USDA Plant Hardiness Zones:** Easily found by entering your zip code on the official USDA Agricultural Research Service website.
**Ecoregion Maps:** The U.S. Environmental Protection Agency (EPA) provides detailed interactive maps and descriptions of ecoregions across the country. State agencies and university extension offices are also excellent resources.

Can I only grow plants native to my specific ecoregion?

While native plants from your ecoregion are often the best choice for thriving with minimal intervention, you can certainly grow other plants. However, understanding your ecoregion helps you anticipate challenges like unsuitable soil pH, drainage, or summer heat/humidity, allowing you to amend your garden or choose more adaptable non-native species wisely.

What if my hardiness zone changes?

The USDA updates its hardiness zone map periodically as climate data changes. If your zone shifts, it means the average extreme minimum winter temperature has changed. This might allow you to grow some previously marginal plants, but also indicates broader climate shifts that could impact other aspects of your ecoregion, like rainfall or summer temperatures.

Are there other factors to consider besides these maps?

Yes, absolutely. Local microclimates within your own yard (e.g., shady spots, south-facing walls, areas protected from wind), soil test results, sun exposure, and drainage are all critical details that influence plant success. These maps provide a regional baseline, but your specific site conditions are the final determinant.

Do these maps apply to all types of plants?

USDA Hardiness Zones are primarily for perennial plants, trees, and shrubs that must survive winter outdoors. Ecoregion maps apply to all plants as they describe the general environmental conditions. Annuals typically aren't rated by hardiness zone as they complete their life cycle in one growing season.

Sources

USDA Plant Hardiness Zone Map
U.S. Environmental Protection Agency (EPA) Ecoregions