Fairfax County, in Virginia, sits in USDA hardiness zone 7b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
The conditions favor cabbage, prickly pear, california poppy, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Fairfax County lies within the Northern Virginia (DC Metro) and the Piedmont — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Fairfax County holds more than one microclimate.
Soils and elevations shift across Fairfax County, so your frost dates and drainage aren't the county average. 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 Fairfax County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Fairfax County — the short answer
Fairfax County, Virginia: USDA zone 7b, about 227 days between hard freezes, across 250K acres.
- USDA zone
- 7b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 29
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 11
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~227
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 250K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 7b is Fairfax County's average, not your lot's — a low corner or a tree line moves it. Against Fairfax County's 227-day season, see what your own ground reads.
Heat in Fairfax County
Across a year, Fairfax County accumulates about 3,659 growing degree days above 50°F, about 75 fewer than the middle Virginia county — ahead of 53 of Virginia’s 133 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Fairfax County
Across Fairfax County, the ground is predominantly Ultisols, where Glenelg, Wheaton, and Codorus are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 4.7–5.5, strongly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Ultisols
Drainage
Well drained
Prime farmland
11%
Hydric soils
5%
Soil still varies lot by lot — soil types explained.
How the ground varies across Fairfax County
The USDA soil survey maps 62% of Fairfax County as well drained — but another 17% drains differently: 10% somewhat poorly drained, 6% moderately well drained.
Glenelg is the most extensive named soil at 23% of mapped acres, then Wheaton (16%) and Codorus (6%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Fairfax County
Each reading below is measured for Fairfax County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Fairfax County are well drained, in hydrologic group C — ground that drains quickly.
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
MeasuredTopsoil across Fairfax County runs about pH 4.7–5.5, on the acidic side.
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
Season length
MeasuredFairfax County runs about 227 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredFairfax County sits in USDA hardiness zone 7b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Fairfax County is in
Fairfax County spans 3 EPA Level III ecoregions — Piedmont (41%), Northern Piedmont (40%) and Southeastern Plains (20%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Fairfax County
We scored all 1,086 plants against Fairfax County's own USDA zone 7b and its own 227-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Virginia profile.
Is it too late to plant in Fairfax County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 29 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 11 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
Documented around Fairfax County
Spotted lanternfly documented 1 miles from Fairfax County, first recorded 2022. What to watch for.
- Japanese beetle101 documented records
- monarch butterfly713 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Fairfax County
USGS estimates 142 lb of Glyphosate on Fairfax County farmland in 2019, its largest by weight, ahead of Dicamba (68 lb) and Triclopyr (39 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Fairfax County — and how to grow with it.
We checked the federal record across Fairfax County — 2,423 documented sites across 7 of the 9 source types we track.
The most significant on record: 8 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Fairfax County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Fairfax County
Closest first, across Fairfax County. Listing isn't leaking, and distance isn't exposure.
- VAARNG-ARMORY-FAIRFAXBrownfields · 0.6 mi
- VSP - DIVISION 7 HEADQUARTERSUnderground Storage Tanks · 0.6 mi
- WOODSON HIGH SCHOOLBrownfields · 0.7 mi
- NORTHERN VA TRAINING CENTERUnderground Storage Tanks · 0.8 mi
- FAIRFAX BAPTIST TEMPLEUnderground Storage Tanks · 0.8 mi
- SAFEWAY STORE #1365Brownfields · 0.8 mi
- T.L.C. DRY CLEANERS INCBrownfields · 0.8 mi
- WOODSON SUPPORT CENTERBrownfields · 0.8 mi
- Fairfax County Woodson Fuel SiteUnderground Storage Tanks · 0.8 mi
- MIKE WERNIGUnderground Storage Tanks · 0.8 mi
- WOODSON HIGH SCHOOLUnderground Storage Tanks · 0.8 mi
- FAIRFAX MEMORIAL PARKUnderground Storage Tanks · 0.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Fairfax County's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Fairfax County.
Total Sites
2,423
across Fairfax County
Risk Level
Elevated
Highest-severity
8 Superfund sites (none NPL-listed)
Sources Checked
across Fairfax County
Severity Distribution
across Fairfax County
Highest-Severity Sites
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.
Check your specific parcel in Fairfax County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Fairfax County average
Your land is one point inside Fairfax County
Everything above resolves to Fairfax County as a whole — one PHZM band and one county frost record, read across 250K acres. Your parcel is one point inside that footprint. 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 county 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 county average.
Your Lot vs the Fairfax County Average
Fairfax County Average
- ●USDA Zones 7b, averaged across Fairfax County
- ●One soil character for all of Fairfax County
- ●Frost dates read at Fairfax County's scale: Mar 29 to Nov 11
YOUR Parcel
- ✓Your exact zone, not Fairfax County's 7b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Fairfax County
Pull a site-specific report for your exact address in Fairfax County, Virginia — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Fairfax County averages can't show:
We read public map data around Fairfax County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Fairfax County average
How we know this about Fairfax County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Fairfax County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Fairfax County
When does frost risk typically end in Fairfax County?
The last hard freeze (28°F) in Fairfax County typically lands around Mar 29, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Apr 19.
How long is the growing season in Fairfax County?
Measured between 28°F hard freezes, Fairfax County sees about 227 frost-free days — roughly Mar 29 through Nov 11, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 19 to Oct 28, about 192 days.
Is the soil safe to grow vegetables in Fairfax County?
The federal record around Fairfax County is a meaningful one — 2,423 documented sites, mostly Underground Storage Tanks entries (1,302), the nearest Brownfields record about 0.6 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Everything above is measured at Fairfax County's scale — its 7b band and its 227-day season. Your yard writes its own version of Fairfax County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Virginia's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Fairfax County’s own scale
9 of the readings below were taken at Fairfax County's own scale — its own ~227-day span between 28°F freezes, the 3 most extensive soil series mapped here and 2,423 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Fairfax County's own USDA hardiness band, zones 7bUSDA PHZM 2023
- Fairfax County's own 28°F hard-freeze dates and its ~227-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Fairfax CountyUSDA NRCS SSURGO
- 2,423 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 0.6 miles outFederal environmental registers
- Fairfax County's boundary and the 250,253 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7b and a ~227-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions Fairfax County spans, Piedmont the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Fairfax County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Fairfax County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Virginia grower plans around — written at state scale, so they stay on the state guidefrom Virginia
What this page can’t tell you
- How the season shifts across Fairfax County — the ~227 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Fairfax County's 250,253 acreswhy one lot differs from the next →
- Which of those 2,423 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Fairfax Countyread your own land →