Greater Pittsburgh / Three Rivers spans USDA hardiness zone 6b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Where three rivers meet and the city's heat pools, Pittsburgh gardens run a season the 6b label understates. Allegheny County averages 229 frost-free days — roughly a month longer than the surrounding southwestern-PA counties (Washington 198, Westmoreland 201) and a world apart from the cold Laurel Highlands just to the east. This is the warm river-valley core: Allegheny plus the Ohio-valley suburbs of Beaver (218 frost-free days), where the Allegheny-Monongahela-Ohio confluence and the urban heat island stretch tomato-and-pepper weather well past what the zone map alone implies. Expect tomato, apple, mountain laurel, and grape to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Greater Pittsburgh / Three Rivers spans Pennsylvania.
Your yard isn't all of Greater Pittsburgh / Three Rivers.
Greater Pittsburgh / Three Rivers spans USDA zones 6b, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Greater Pittsburgh / Three Rivers — soil, climate, flood, and parcel records. How we handle your address.
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Greater Pittsburgh / Three Rivers — the short answer
Greater Pittsburgh / Three Rivers: USDA zones 6b, 218–229 frost-free days, in Pennsylvania.
- USDA zones
- 6b
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 218–229 days
- NOAA Regional Climate Centers ACIS, 1991-2020
- Counties
- 2
- US Census TIGER/Line 2025
- Region type
- County cluster
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. Where a region publishes no measured season, no season figure is shown.
Hardiness Zone Range
What Grows in Greater Pittsburgh / Three Rivers
Plants matched to Greater Pittsburgh / Three Rivers' USDA zones 6b, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of Greater Pittsburgh / Three Rivers
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets Greater Pittsburgh / Three Rivers’s USDA zones 6b — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across Greater Pittsburgh / Three Rivers
The USDA soil survey maps this ground county by county. These are those records weighted by land area across two member counties — this region’s own profile, not a state figure.
The ground is predominantly Ultisols, at 47% of mapped acres, followed by Alfisols (33%), Inceptisols (14%) and Entisols (5%). Five soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Gilpin, Culleoka, and Wharton.
51% of those acres are well drained, and another 25% moderately well drained, 3% somewhat poorly drained. Topsoil pH runs 5.0–6.2 between the lowest and the highest county on record. 11% of the footprint is classed prime farmland.
Soil order
Ultisols
Drainage
Well drained
Topsoil pH
5.0–6.2
Hydric soils
3%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Beaver County holds the most wetland ground here, at 4% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in Greater Pittsburgh / Three Rivers
The soil survey reads this ground county by county, and the readings above are those records summed across Greater Pittsburgh / Three Rivers. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records51% of the mapped acres across Greater Pittsburgh / Three Rivers are well drained — ground that drains quickly. That is area-weighted across all two of its mapped counties.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across Greater Pittsburgh / Three Rivers runs pH 5.0–6.2 — acidic in all two of them.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across Greater Pittsburgh / Three Rivers — and how to grow with it.
Across Greater Pittsburgh / Three Rivers' 2 counties the federal record holds 5,661 documented sites, mostly Underground Storage Tanks (2,722), Brownfields (2,434) and Toxics Release Inventory (336). The heaviest single county is Allegheny County, with 4,863.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to Greater Pittsburgh / Three Rivers to see which records sit where you actually grow.
Sources Checked
Summed across the 2 counties in Greater Pittsburgh / Three Rivers
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •TRI facilities report what they release. Check the wind — downwind beds catch more of it.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside Greater Pittsburgh / Three Rivers
Everything above resolves to Greater Pittsburgh / Three Rivers as a whole — a footprint spanning USDA zones 6b. Your parcel sits in exactly one of them. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at region scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better regional average.
Your Lot vs Greater Pittsburgh / Three Rivers Average
Greater Pittsburgh / Three Rivers Average
- ●USDA Zones 6b, averaged across Greater Pittsburgh / Three Rivers
- ●One soil character for all of Greater Pittsburgh / Three Rivers
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Greater Pittsburgh / Three Rivers' 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Greater Pittsburgh / Three Rivers
Pull a site-specific report for your exact address in Greater Pittsburgh / Three Rivers — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Greater Pittsburgh / Three Rivers averages can't show:
We read public map data around Greater Pittsburgh / Three Rivers — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not Greater Pittsburgh / Three Rivers average
How we know this about Greater Pittsburgh / Three Rivers
The boundary: a cluster of neighboring counties. Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about Greater Pittsburgh / Three Rivers
What hardiness zone is Greater Pittsburgh / Three Rivers?
Greater Pittsburgh / Three Rivers spans USDA hardiness zones 6b, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in Greater Pittsburgh / Three Rivers?
Measured between 28°F hard freezes, Greater Pittsburgh / Three Rivers' counties mostly run 221 to 226 frost-free days, median 224 (NOAA Regional Climate Centers ACIS, 1991–2020, over 2 member counties). That 5-day spread is the honest read — no single season describes 2 counties, and each county guide below carries its own.
When does frost risk end in Greater Pittsburgh / Three Rivers?
Across Greater Pittsburgh / Three Rivers, the middle half of member counties see their last 28°F hard freeze between Apr 2 and Apr 6 (median Apr 4), and their first fall freeze between Nov 13 and Nov 14. Those are hard freezes, not the last light frost: tender transplants wait for about Apr 25, and elevation decides which end of a 4-day spread you garden in.
What grows well in Greater Pittsburgh / Three Rivers?
Greater Pittsburgh / Three Rivers' conditions suit plants such as Tomato, Apple, Mountain Laurel, Grape, Mushroom. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is Greater Pittsburgh / Three Rivers defined?
Greater Pittsburgh / Three Rivers is defined here as a curated cluster of 2 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does Greater Pittsburgh / Three Rivers cover?
Greater Pittsburgh / Three Rivers spans Pennsylvania. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Appalachia, Northern Tier (north-central Pennsylvania high plateau), The Poconos, Cumberland Valley, Brandywine Valley, and Greater Philadelphia share at least one state with Greater Pittsburgh / Three Rivers. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at Greater Pittsburgh / Three Rivers’s own scale
6 of the readings below were taken at Greater Pittsburgh / Three Rivers' own scale — the zone 6b band across its footprint, a median 224-day season across its 2 counties and 5,661 documented federal contamination records across its 2 counties, 4,863 of them in Allegheny County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 6b aggregated across all 2 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 2 counties this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 2 counties run 221 to 226 frost-free days, median 224NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 5,661 documented federal contamination records across its 2 counties, 4,863 of them in Allegheny County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 47% Ultisols, topsoil pH 5.0–6.2, area-weighted across its 2 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 6bfrom Pennsylvania
What this page can’t tell you
- Which end of the 5-day range your ground sits at — 221 days at one extreme, 226 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore Greater Pittsburgh / Three Rivers
State growing guides
Counties in this region
Other growing regions across Pennsylvania
The vast eastern mountain region of steep hollows, thin acidic soils, and short upland seasons — apples, brambles, ramps, and forest crops on hard-won ground. (Union of the core Appalachian ecoregions.)
Pennsylvania's coldest, shortest-season ground: the glaciated high plateau of the North Central Appalachians (EPA Level III ecoregion 62), where Potter, Tioga, McKean, and Cameron counties all sit in USDA zone 5b with only 160-166 frost-free days — Potter's 160 is the state minimum, roughly five weeks shorter than Pennsylvania's median season. This is the "PA Wilds" / "God's Country" cold pocket: cold-air-pooling ridges and hollows, thin acidic plateau soils, and a last frost that holds into the first week of May. The generic multi-state Appalachia region spans a far milder 5b-8b across a 211-day median season and never resolves this plateau's short, cold window.
The Pocono Mountains of northeastern Pennsylvania — Carbon, Monroe, Pike, and Wayne counties — span USDA hardiness zones 6a to 6b with frost-free growing seasons of roughly 167 to 198 days.
The Cumberland Valley is the Great Valley's northern anchor — the same limestone floor that runs south into the Shenandoah, but colder-wintered and shorter-seasoned, and split by the Mason-Dixon line across Cumberland and Franklin counties in Pennsylvania and Washington County in Maryland. Scoped to just those three, the picture tightens to a uniform USDA zone 7a and a 215-to-219-day frost-free season — last frost in early April, first in early November — steadier than the wide 5b-8b range the broader Appalachian page has to average across. The valley reads in two halves: a flat limestone floor where cold air pools on clear spring nights, long given over to dairy pasture, hay, and grain, and the elevated Blue Ridge benches of South Mountain along the eastern edge, where good cold-air drainage has kept apple and peach orchards in business for generations. Those same well-drained slopes carry the federally recognized Cumberland Valley AVA's wine grapes.
The Brandywine Valley traces the Brandywine Creek watershed (USGS hydrologic unit 02040205) from Chester County, Pennsylvania into New Castle County, Delaware, spanning USDA zones 7a to 7b and a frost-free season of roughly 213 to 241 days.
Pennsylvania's only USDA zone 7b ground — the warmest, longest-season corner of the state. Philadelphia County runs about 250 frost-free days and Delaware County about 239, against a statewide county median of 197, so the tidal Delaware–Schuylkill corridor and the city's urban heat island buy growers here a full zone and roughly a month of extra season over the 7a suburbs just north. Last frost typically clears by mid-to-late March and first frost holds off until late November.