What is a USDA hardiness zone?

A USDA hardiness zone is a geographic area defined by the average annual minimum winter temperature. The USDA Plant Hardiness Zone Map divides North America into 13 zones, each representing a 10-degree Fahrenheit range. Gardeners use these zones to determine which perennial plants can survive winter in their area.

How do I find my hardiness zone?

You can find your hardiness zone using the USDA Plant Hardiness Zone Map at planthardiness.ars.usda.gov. Enter your ZIP code to see your zone. Many gardening websites and apps, including PlotMyGarden, can also detect your zone automatically using your location. Zone 6b, for example, indicates an average minimum winter temperature of -5 to 0 degrees Fahrenheit.

Can I grow plants rated for a different zone?

Yes, with some limitations. Plants rated for warmer zones may survive with winter protection like mulching, cold frames, or growing in containers that can be moved indoors. Plants rated for colder zones will generally grow well but may not experience enough cold hours for certain fruits. Microclimates within your garden can also create pockets a half-zone warmer or colder than your official designation.

What is a microclimate and why does it matter?

A microclimate is a small area where the climate differs from the surrounding region. South-facing walls absorb heat and create warmer pockets. Low areas collect cold air and frost. Urban areas are often warmer than rural ones due to heat from buildings and pavement. Understanding your garden's microclimates lets you push zone boundaries and grow plants that might not survive in exposed locations.

How accurate are hardiness zone maps?

Hardiness zone maps provide a useful baseline but have limitations. They are based on average minimum temperatures over 30 years, so extreme winters can still damage plants within their rated zone. They also don't account for soil drainage, snow cover, humidity, or summer heat. The USDA updates the map periodically, most recently in 2023, reflecting shifting climate patterns.

Do urban gardens have different hardiness zones?

Urban areas typically experience the heat island effect, where concrete, asphalt, and buildings absorb and retain heat. This can make city gardens effectively one half-zone warmer than surrounding rural areas. An urban gardener in zone 6b might successfully grow plants rated for zone 7a that would fail in nearby countryside gardens.

USDA Hardiness Zones

Understanding your climate zone

What Are Hardiness Zones?

The USDA Plant Hardiness Zone Map is the standard used by gardeners and growers to determine which plants are most likely to thrive at a given location. The map divides North America (and can be applied globally) into 13 zones based on the average annual minimum winter temperature.

Each zone represents a 10-degree Fahrenheit (approximately 5.5-degree Celsius) range, further divided into "a" (colder half) and "b" (warmer half) sub-zones. Knowing your zone helps you select perennials, trees, and shrubs that can survive your winters, and plan annual planting schedules effectively.

While hardiness zones focus on cold tolerance, successful gardening also depends on heat tolerance, rainfall patterns, soil type, and microclimates within your property. Use zone data as a starting point, then adjust based on your local conditions.

Sources: USDA Agricultural Research Service Plant Hardiness Zone Map (planthardiness.ars.usda.gov); American Horticultural Society heat zone resources; State Cooperative Extension Service publications on regional climate adaptation.

Find Your Zone

Detect your hardiness zone automatically using your device location, or select a zone manually below.

or select manually:

Tips for Gardening in Any Zone

Understand Microclimates

Your garden may contain several microclimates within a small area. South-facing walls absorb and radiate heat, creating warmer pockets. Low-lying areas collect cold air and frost. Mapping these differences lets you push the boundaries of your official zone by placing tender plants in protected spots.

Extend Your Season

Cold frames, row covers, and cloches can effectively move your garden one full zone warmer. A simple cold frame over a raised bed can let you start planting weeks earlier in spring and harvest well into winter, even in zones 4 and 5.

Urban Heat Islands

Cities are typically warmer than surrounding rural areas due to heat absorbed by concrete, asphalt, and buildings. Urban gardeners may find they can grow plants rated for one zone warmer than their official designation suggests.

Elevation Matters

Temperature drops roughly 1°C for every 150 meters of elevation gain. A garden on a hillside may be a full zone colder than one in the valley below, even if they share the same official zone designation on a broad-scale map.

All Zones at a Glance

Click any zone to see which plants from our database are suitable.

Vladimir Kusnezow

Gardener and Software Developer

Zone 6b gardener. Growing vegetables and fruits in soil and hydroponics for 6 years. I built PlotMyGarden to plan my own gardens.

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