Washtenaw County, in Michigan, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Expect cabbage, hazelnut, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Washtenaw County lies within Metro Detroit & Southeast Michigan — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Washtenaw County holds more than one microclimate.
Soils and elevations shift across Washtenaw 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 Washtenaw County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Washtenaw County — the short answer
Washtenaw County, Michigan: USDA zone 6a, about 183 days between hard freezes, across 452K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 20
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~183
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 452K 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 6a is Washtenaw County's average, not your lot's — a low corner or a tree line moves it. Against Washtenaw County's 183-day season, see what your own ground reads.
Heat in Washtenaw County
Across a year, Washtenaw County accumulates about 2,509 growing degree days above 50°F, about 409 more than the middle Michigan county — ahead of 72 of Michigan’s 83 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 Washtenaw County
Across Washtenaw County, the ground is predominantly Alfisols, where Wawasee, Fox, and Spinks are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.3–6.5, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
21%
Hydric soils
24%
Soil still varies lot by lot — soil types explained.
How the ground varies across Washtenaw County
The USDA soil survey maps 46% of Washtenaw County as well drained — but another 51% drains differently: 19% somewhat poorly drained, 15% very poorly drained.
Wawasee is the most extensive named soil at 13% of mapped acres, then Fox (7%) and Spinks (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 Washtenaw County
Each reading below is measured for Washtenaw 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 Washtenaw County are well drained, in hydrologic group B — 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 Washtenaw County runs about pH 6.3–6.5, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Wet ground
MeasuredAbout 24% of Washtenaw County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Season length
MeasuredWashtenaw County runs about 183 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
The kind of country Washtenaw County is in
Washtenaw County spans 3 EPA Level III ecoregions — Eastern Corn Belt Plains (69%), Southern Michigan/Northern Indiana Drift Plains (18%) and Huron/Erie Lake Plains (13%). 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 Washtenaw County
We scored all 1,086 plants against Washtenaw County's own USDA zone 6a and its own 183-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 Michigan profile.
Is it too late to plant in Washtenaw County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Mar 23; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 20 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 20 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
Documented around Washtenaw County
Survey cells within 31 miles of Washtenaw County checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 34 miles off. What to watch for.
- Japanese beetle36 documented records
- monarch butterfly103 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Washtenaw County
USGS estimates 94,532 lb of Glyphosate on Washtenaw County farmland in 2019, its largest by weight, ahead of Atrazine (19,774 lb) and Metolachlor & Metolachlor-s (15,626 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 Washtenaw County — and how to grow with it.
We checked the federal record across Washtenaw County — 2,082 documented sites across 6 of the 9 source types we track.
The most significant on record: 17 Superfund sites. 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 Washtenaw 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 Washtenaw County
Closest first, across Washtenaw County. Listing isn't leaking, and distance isn't exposure.
- SCIO TOWNSHIPPFAS · 0.6 mi
- 03S05E09BBAA01Nitrate · 0.9 mi
- 02S05E34BDDB01Nitrate · 1.1 mi
- SCIO TOWNSHIP HERBICIDE SPILLSuperfund · 1.2 mi
- 03S05E02CCCB01Nitrate · 1.5 mi
- 02S05E29DCCD01Nitrate · 1.6 mi
- SUS161-33Nitrate · 1.8 mi
- Alfred RentschlerUnderground Storage Tanks · 2.0 mi
- UNIVERSITY OF MICHIGANBrownfields · 2.3 mi
- DANMAR PRODUCTS INCBrownfields · 2.3 mi
- INTERNATIONAL TRANSMISSION COMPANY LLCBrownfields · 2.3 mi
- DETROIT EDISON COBrownfields · 2.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Washtenaw 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 Washtenaw County.
Sources Checked
across Washtenaw County
Severity Distribution
across Washtenaw County
Highest-Severity Sites
Know Before You Grow
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Washtenaw 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 Washtenaw County average
Your land is one point inside Washtenaw County
Everything above resolves to Washtenaw County as a whole — one PHZM band and one county frost record, read across 452K 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 Washtenaw County Average
Washtenaw County Average
- ●USDA Zones 6a, averaged across Washtenaw County
- ●One soil character for all of Washtenaw County
- ●Frost dates read at Washtenaw County's scale: Apr 20 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Washtenaw County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Washtenaw County
Pull a site-specific report for your exact address in Washtenaw County, Michigan — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Washtenaw County averages can't show:
We read public map data around Washtenaw County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Washtenaw County average
How we know this about Washtenaw 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 Washtenaw County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Washtenaw County
When does frost risk typically end in Washtenaw County?
The last hard freeze (28°F) in Washtenaw County typically lands around Apr 20, 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 May 11.
How long is the growing season in Washtenaw County?
Measured between 28°F hard freezes, Washtenaw County sees about 183 frost-free days — roughly Apr 20 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 11 to Oct 6, about 148 days.
Is the soil safe to grow vegetables in Washtenaw County?
The federal record around Washtenaw County is a meaningful one — 2,082 documented sites, mostly Brownfields entries (933), the nearest PFAS 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 Washtenaw County's scale — its 6a band and its 183-day season. Your yard writes its own version of Washtenaw 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 Michigan's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Washtenaw County’s own scale
9 of the readings below were taken at Washtenaw County's own scale — its own ~183-day span between 28°F freezes, the 3 most extensive soil series mapped here and 2,082 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Washtenaw County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Washtenaw County's own 28°F hard-freeze dates and its ~183-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Washtenaw CountyUSDA NRCS SSURGO
- 2,082 documented contamination sites inside the county boundary, distance-sorted from its center — the closest PFAS record about 0.6 miles outFederal environmental registers
- Washtenaw County's boundary and the 451,849 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~183-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions Washtenaw County spans, Eastern Corn Belt Plains the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Washtenaw County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Washtenaw County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Michigan grower plans around — written at state scale, so they stay on the state guidefrom Michigan
What this page can’t tell you
- How the season shifts across Washtenaw County — the ~183 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 Washtenaw County's 451,849 acreswhy one lot differs from the next →
- Which of those 2,082 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 Washtenaw Countyread your own land →