Gardening in Pennsylvania

Hardiness zones in Pennsylvania

Pennsylvania spans USDA hardiness zones 5b through 8a, based on data from 159 weather stations across the state. A hardiness zone number describes one thing only: the average coldest temperature a location reaches each winter. It does not describe summer heat, rainfall, or soil type. Zone 5b is the coldest zone found in the state, and zone 8a is the mildest. Most of Pennsylvania falls somewhere between these two extremes, in zones 6a through 7b. Check which zone covers your location before you choose perennials, shrubs, or trees meant to survive the winter outdoors. A plant rated for your zone, or a colder one, should survive a typical winter low in your area. A plant rated only for a warmer zone may need shelter or indoor care.

• Zone 5b
• Zone 6a
• Zone 6b
• Zone 7a
• Zone 7b
• Zone 8a

Frost dates

Frost dates mark the start and end of your safe outdoor growing window. Across Pennsylvania, the last spring frost falls as early as March 30 in the mildest spots. In the coldest spots, it can linger as late as May 24. The first fall frost arrives as early as September 27 in colder areas and as late as November 17 in milder ones. These are 50 percent probability dates, meaning frost has about an even chance of happening on or after that date. Your own risk could run earlier or later than a statewide figure. Pennsylvania's frost dates vary by more than seven weeks from one station to another. Wait until after your local last frost date before you move tender seedlings and warm-season vegetables outdoors. Plan to harvest, cover, or bring in frost-sensitive plants before your local first frost date in fall. Check a frost date calculator or your local extension office for the figure specific to your town. A single statewide range cannot tell you the exact date for your yard.

Climate

The growing season in Pennsylvania, measured from last spring frost to first fall frost, ranges widely across the state. Some locations see as few as 126 frost-free days a year, while others see as many as 232. That is a gap of more than three months between the shortest and longest season recorded in the state's climate data. This spread comes from data gathered across 159 weather stations, so it reflects real differences between towns rather than a single average. A short growing season favors fast-maturing crops and cold-hardy perennials. A long one gives slower vegetables and tender plants more time to finish before frost. This page's figures cover only hardiness zones, frost dates, and season length. They do not cover summer heat, humidity, rainfall, or soil type, so check those separately for your area before you plan a garden. Because Pennsylvania's zones run from 5b to 8a and its frost-free season spans 126 to 232 days, no single climate description fits the whole state. Use the zone and frost figures for your own location, not a statewide average, when you decide what to plant and when.

Season length

The frost-free growing season in this state runs from 126 days in its shortest locations to 232 days in its longest. That span comes directly from the last and first frost dates recorded across the state's 159 weather stations. A gardener in a short-season spot needs to pick quick-maturing varieties and may want to start seeds indoors before the last frost. A gardener in a long-season spot has more room to grow crops that need a full summer. That includes late melons or long-season peppers. Count the days between your own local last and first frost dates to find your real planting window. Don't just rely on the statewide range alone.