USDA Hardiness Zones in Pennsylvania Explained

Pennsylvania covers three full USDA hardiness zones — from 5a in the mountains to 7a around Philadelphia. Your zone tells you the coldest temperature your area typically hits in winter, which determines what plants can survive year-round in your yard.

If you’ve ever bought a perennial, fruit tree, or shrub and watched it die the first winter, there’s a good chance it wasn’t rated for your zone. Getting this right saves you money and frustration.

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What USDA Hardiness Zones Actually Mean

The USDA Plant Hardiness Zone Map divides North America into zones based on average annual extreme minimum winter temperature. Each zone spans a 10°F range, and each half-zone (a/b) spans 5°F.

In plain English: your zone number tells you the coldest it typically gets in your area during winter. That’s it. It doesn’t account for summer heat, humidity, rainfall, or soil type — but it’s the single best shortcut for knowing whether a plant will survive your winters.

Here’s what the zones mean in degrees:

When a plant tag says “hardy to zone 6,” it means the plant can survive winter lows down to -10°F. If you’re in zone 5a where it hits -20°F, that plant probably won’t make it.

Pennsylvania’s Zone Map by Region

You can look up your exact zone by zip code on the USDA Plant Hardiness Zone Map, but here’s the big picture for PA:

Zone 5a — Northern Mountains and Poconos

Coldest part of the state. Winter lows regularly dip to -20°F. This includes Bradford, parts of Potter and Tioga counties, the highest elevations of the Poconos, and scattered mountain ridgetops.

Gardening here means shorter seasons and tougher plant selection. You need varieties that can handle serious cold — and even then, a polar vortex year can push temps below the zone 5a floor.

What grows well in zone 5a: – Cold-hardy fruit trees: apple (Honeycrisp, Liberty), sour cherry, cold-hardy pear – Berries: blueberries, raspberries, currants, gooseberries – Vegetables: anything, but start indoors early and use season extension – Trees: sugar maple, red oak, white pine, blue spruce, hemlock – Perennials: coneflower, black-eyed Susan, daylily, hosta, sedum

Zone 5b — Western PA Highlands and Northern Tier

Covers much of the rural western half of the state — Indiana, Clearfield, Elk, and Cameron counties, plus the Scranton/Wilkes-Barre area and much of the northern tier. Winter lows reach -15°F to -10°F.

This is where most of PA’s “it depends” answers live. You can grow a wider range than zone 5a, but you still need to pay attention to variety selection and be realistic about what will survive December through February.

What grows well in zone 5b: – Everything from 5a, plus: peach trees (with care), sweet cherry (sheltered spots), grape vines (cold-hardy varieties like Concord) – More hydrangea options — panicle hydrangeas (like Limelight) do great here – A wider range of ornamental grasses and native perennials

Zone 6a — Pittsburgh, Harrisburg, and Suburban Valleys

This is the most common zone in Pennsylvania. It covers the Pittsburgh metro, Harrisburg, Lancaster, much of the Lehigh Valley, and the lower-elevation valleys throughout central PA. Winter lows range from -10°F to -5°F.

Zone 6a is the sweet spot for PA gardening — cold enough for good dormancy periods (which fruit trees need), warm enough for a solid 180+ day growing season in most spots.

What grows well in zone 6a: – Fruit trees: apples, pears, peaches, plums, cherries (sweet and sour) – Berries: everything — blueberries, strawberries, raspberries, blackberries – Expanded perennial options: lavender (with good drainage), more rose varieties, butterfly bush – Native trees: tulip poplar, American beech, red maple, flowering dogwood – Lawn: cool-season grasses thrive here — tall fescue and Kentucky bluegrass are the go-to mix

Zone 6b — Eastern Suburbs and Warmer Valleys

Covers the Philadelphia suburbs, Reading, Allentown, York, and warmer pockets of central PA. Winter lows only reach -5°F to 0°F. You get more planting options and a longer season here.

What grows well in zone 6b: – Everything from 6a, plus: fig trees (with winter protection), some borderline zone 7 plants – Larger hydrangea variety selection — bigleaf hydrangeas (mopheads) are more reliable here than in 5b/6a – Crape myrtle (some cold-hardy varieties survive here with mulching) – Longer-season vegetables like sweet potatoes and melons do better here than in western PA

Zone 7a — Philadelphia Metro

The warmest zone in Pennsylvania, covering Philadelphia proper and the immediate southeastern suburbs. Winter lows only reach 0°F to 5°F. You’re essentially gardening in a mid-Atlantic climate with a growing season that can stretch past 230 days.

What grows well in zone 7a: – Everything from 6b, plus: fig trees (often without winter protection), southern magnolia, crape myrtle more reliably – Longer-season warm crops like okra, sweet potatoes, and peanuts have enough time to mature here – More ornamental options: camellias (fall-blooming varieties), some gardenias with protection – Fall planting can continue later into the year — you’ve got until late November before it gets truly cold

How to Find Your Exact Zone

The general regional breakdown above gets you close, but microclimates can shift your effective zone by a half-zone or more. A hilltop garden in “zone 6a” might functionally be 5b, while a south-facing yard against a brick wall in the same zip code might behave like 6b.

The best way to find your zone:

1. Check the official USDA map at planthardiness.ars.usda.gov — enter your zip code for the most precise reading.
2. Cross-reference with your frost dates. Your frost dates (covered in our Pennsylvania frost dates guide) give you the other half of the picture — not just how cold it gets, but how long your growing window is.
3. Observe your own yard. If plants rated for your zone keep dying in the same spot, you might have a colder microclimate. If zone-pushing plants keep surviving, you might be warmer than the map says.

What Your Zone Doesn’t Tell You

The USDA zone map is useful, but it only measures one thing: winter cold. It doesn’t account for several factors that matter a lot in PA:

• Summer heat. A zone 6a garden in Pittsburgh has very different summers than a zone 6a garden in Harrisburg. Penn State’s agricultural climate data tracks heat and humidity patterns across the state.
• Clay soil. Most of PA sits on clay-heavy soil regardless of zone. This affects drainage, root health, and which plants actually thrive versus merely survive. A plant that’s “hardy to zone 6” might still struggle if it needs well-drained soil and you’ve got compacted clay.
• Rainfall. PA averages 38–45 inches per year, but it varies by region. The mountains get more, the southeast gets less. Some plants that are cold-hardy enough for your zone may still fail if they need drier conditions.
• Frost pocket risk. Valleys and low-lying areas can be a full zone colder on clear, calm nights than surrounding hills — even if the USDA map shows them as the same zone.

This is why experienced PA gardeners use zone as a starting point, not the whole answer. Pair it with your frost dates, soil type, and microclimate observations for the full picture.

Buying Plants: How to Read Zone Labels

Every plant tag or nursery listing shows a hardiness zone range like “Zones 4–8” or “Zones 6–9.” Here’s how to read it:

• The first number is the coldest zone where the plant survives winter. If it says “Zone 5,” the plant handles -20°F.
• The second number is the warmest zone where the plant does well. Plants need a certain amount of winter chill — if your zone is too warm, they might not flower or fruit properly.
• Pick plants rated for your zone or one zone colder. If you’re in zone 6a, plants rated “Zone 5–8” are a safer bet than “Zone 6–9.” That extra zone of cold hardiness gives you insurance against harsh winters.

A quick soil thermometer or min/max thermometer in your garden gives you real data about your yard’s actual conditions — way more useful than relying on the USDA map alone.

Common Zone Mistakes PA Gardeners Make

Buying by the picture, not the tag. That gorgeous crape myrtle at the garden center might be rated zone 7–9. If you’re in zone 6a Pittsburgh, it’s probably not going to make it past January. Always check the zone rating before you get attached.

Ignoring the “b” in your zone. There’s a meaningful difference between 6a and 6b — that 5°F gap determines whether borderline plants like bigleaf hydrangeas and fig trees survive your winters. Know which half-zone you’re in.

Treating the whole yard as one zone. The south side of your house against a brick wall might be a full zone warmer than the north-facing bed on the shady side. Map your yard’s microclimates and plant accordingly — it’s one of the easiest ways to grow things the zone map says you can’t.

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