Hopkinton, Iowa, sits in USDA hardiness zone 5a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Hopkinton, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Hopkinton lot. 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 Hopkinton — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Hopkinton — the short answer
Hopkinton, Iowa: USDA zone 5a, about 183 days between hard freezes, across 411 acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~183
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 411 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 5a is Hopkinton's average, not your lot's — a low corner or a tree line moves it. Against Hopkinton's 183-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Hopkinton
Each reading below is measured for Hopkinton itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHopkinton 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
Winter hardiness
MeasuredHopkinton sits in USDA hardiness zone 5a.
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 Hopkinton is in
Hopkinton sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Hopkinton's own centroid rather than borrowed from Delaware County.
What Grows in Hopkinton
Every plant below cleared Hopkinton's own zone 5a and its 183-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Hopkinton?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 21; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 18 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 18 — 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.
What's on the federal record near Hopkinton
Closest first, within ~10 miles of Hopkinton. Listing isn't leaking, and distance isn't exposure.
- HOPKINTON MUNICIPAL UTILITIESUnderground Storage Tanks · 450 ft
- SCHUMAN''S TRUCK & AUTOUnderground Storage Tanks · 500 ft
- SWISS VALLEY FARMS COToxics Release Inventory · 600 ft
- DETTBARN DXUnderground Storage Tanks · 700 ft
- HARRIS ELECTRICAL SERVICE INCUnderground Storage Tanks · 700 ft
- DAVID W BUCHHEITUnderground Storage Tanks · 700 ft
- MAURICE KIRKWOODUnderground Storage Tanks · 700 ft
- CROP MATE COMPANYUnderground Storage Tanks · 700 ft
- DELAWARE COUNTY ENGINEERUnderground Storage Tanks · 800 ft
- HOPKINGON PROPERTYUnderground Storage Tanks · 950 ft
- BREMER COUNTY HIGHWAY DEPTUnderground Storage Tanks · 1800 ft
- SWISS VALLEY AG SERVICEUnderground Storage Tanks · 1800 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Hopkinton'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 Hopkinton.
Total Sites
123
within ~10 miles of Hopkinton
Risk Level
Moderate
Highest-severity
6 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Hopkinton
Severity Distribution
within ~10 miles of Hopkinton
Highest-Severity Sites
Know Before You Grow
- •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.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
Check your specific parcel in Hopkinton
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 Hopkinton average
Your land is one point inside Hopkinton
Everything above resolves to Hopkinton as a whole — one PHZM band and one 28°F frost record, read across 411 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 city 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 local average.
Your Lot vs the Hopkinton Average
Hopkinton Average
- ●USDA Zones 5a, averaged across Hopkinton
- ●One soil character for all of Hopkinton
- ●Frost dates read at Hopkinton's scale: Apr 18 to Oct 18
YOUR Parcel
- ✓Your exact zone, not Hopkinton's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Hopkinton
Pull a site-specific report for your exact address in Hopkinton, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hopkinton averages can't show:
We read public map data around Hopkinton — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hopkinton average
How we know this about Hopkinton
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Hopkinton’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Hopkinton
When does frost risk typically end in Hopkinton?
The last hard freeze (28°F) in Hopkinton typically lands around Apr 18, 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 9.
When is the first frost in Hopkinton?
The first hard freeze (28°F) in Hopkinton typically arrives around Oct 18, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 4, so the watching starts about Sep 18 — about 183 days after the spring freeze cleared.
How long is the growing season in Hopkinton?
Measured between 28°F hard freezes, Hopkinton sees about 183 frost-free days — roughly Apr 18 through Oct 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 9 to Oct 4, about 148 days.
Is the soil safe to grow vegetables in Hopkinton?
The federal record around Hopkinton shows 123 documented sites, mostly Underground Storage Tanks entries (69), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Hopkinton?
From about Sep 18 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 18 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 18. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hopkinton's scale — its 5a band and its 183-day season. Your yard writes its own version of Hopkinton's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Hopkinton’s own scale
6 of the readings below were taken at Hopkinton's own scale — its own ~183-day season between 28°F freezes, the 411 acres it covers and 123 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Hopkinton's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Hopkinton's own 28°F hard-freeze dates, about Apr 18 and Oct 18 and the ~183-day span between themNOAA 1991–2020 Climate Normals
- 123 documented contamination sites on the federal record near Hopkinton, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Hopkinton's boundary and the 411 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~183-day seasonGrowable Ground crop-matching engine
- The ecoregion at Hopkinton's own centroid, the Western Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Hopkinton's 411 acres read through its county's SSURGO summaryfrom Delaware County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Delaware County
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Delaware County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hopkinton's 411 acreswhy one lot differs from the next →
- Which side of Hopkinton you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 411 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Hopkinton-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaHopkinton sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides