The growing zone for Western New York is highly localized. Understanding the growing zone is the first step toward successful gardening, as it determines which perennial plants can survive the region’s winter temperatures. Western New York, encompassing areas along Lake Erie and Lake Ontario, is characterized by a range of plant hardiness classifications defined by the United States Department of Agriculture (USDA) system.
Understanding the USDA Plant Hardiness Zone System
The USDA Plant Hardiness Zone Map is the standard reference tool for assessing a plant’s ability to survive winter. This system is based entirely on the average annual minimum winter temperature, which is the most important factor for perennial survival. The map divides North America into 13 zones, each representing a 10-degree Fahrenheit range of extreme low temperatures.
Each major zone is broken down into two sub-zones, ‘a’ and ‘b,’ narrowing the temperature range to 5 degrees Fahrenheit. This provides a more precise measure of cold tolerance. For example, Zone 6 has an average annual minimum temperature range of -10°F to 0°F.
The colder half, Zone 6a, signifies a minimum range of -10°F to -5°F, while the warmer half, Zone 6b, indicates a range of -5°F to 0°F. The hardiness zone helps gardeners select plants that can withstand the coldest expected temperature. The system does not account for factors like summer heat, rainfall, or the length of the growing season.
The Specific Zones of Western New York
Western New York contains a distinct gradient of plant hardiness zones, primarily ranging from 5b to 6b. The most populated areas immediately bordering the Great Lakes benefit from the warmest classifications. Cities like Buffalo and Rochester, along with the immediate shoreline counties of Erie, Niagara, and Monroe, are predominantly situated in the milder Zone 6b.
This Zone 6b classification means the average annual extreme low temperature is between -5°F and 0°F, allowing for a wider selection of ornamental plants and certain fruit trees to survive the winter. For instance, some varieties of reblooming azaleas or specific roses are rated to survive in the 6b range. Moving inland, the zones quickly transition to cooler classifications.
The interior and southern-tier counties, such as Allegany, Cattaraugus, and Wyoming, fall into the colder Zone 5b. Zone 5b indicates the average annual minimum temperature drops to between -15°F and -10°F, requiring greater cold hardiness. Perennials like New England aster and American black elderberry are resilient in this colder range. Areas between the lakeshore and high elevations, particularly in the Finger Lakes region, are classified as Zone 6a (-10°F to -5°F).
Key Climate Factors Creating Local Zone Variation
The variation in hardiness zones across Western New York results from several localized climate factors. The most influential factor is the Great Lakes Effect, where the vast thermal mass of Lake Erie and Lake Ontario moderates the local climate. During winter, the water remains warmer than the air, releasing heat that prevents shore temperatures from plummeting to the extreme lows seen inland.
This heat exchange creates a narrow band of warmer air that buffers lakeshore communities against cold snaps, contributing to the Zone 6a and 6b classifications. The same effect is responsible for lake-effect snow bands, though snowfall does not change the minimum temperature calculation. A second significant factor is elevation and topography, which affects inland areas.
The higher elevations of the Allegany Plateau, which forms the southern boundary, cool more rapidly and hold cold air masses. Areas above 1,000 feet in counties like Allegany and Cattaraugus lose the lakes’ moderating influence and experience lower minimum temperatures, resulting in the colder Zone 5b designation. Another element is the Urban Heat Island effect, which contributes to slightly warmer zones within major metropolitan centers. Cities like Buffalo and Rochester retain heat more effectively than surrounding rural areas, subtly elevating the minimum winter temperature in the urban core.