Clarkson Valley, Missouri, sits in USDA hardiness zone 7a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Crops well matched to these conditions include cabbage, hazelnut, california poppy, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Clarkson Valley, 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 Clarkson Valley 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 Clarkson Valley — soil, climate, flood, and parcel records. How we handle your address.
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Clarkson Valley — the short answer
Clarkson Valley, Missouri: USDA zone 7a, about 240 days between hard freezes, across 2K acres of city.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~240
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 2K 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 7a is Clarkson Valley's average, not your lot's — a low corner or a tree line moves it. Against Clarkson Valley's 240-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Clarkson Valley
Each reading below is measured for Clarkson Valley itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredClarkson Valley runs about 240 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
MeasuredClarkson Valley sits in USDA hardiness zone 7a.
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 Clarkson Valley is in
Clarkson Valley sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Clarkson Valley's own centroid rather than borrowed from St. Louis County.
What Grows in Clarkson Valley
Every plant below cleared Clarkson Valley's own zone 7a and its 240-day season. Each card opens that plant's Missouri profile. How we score.
Is it too late to plant in Clarkson Valley?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Feb 22; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 22 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 17 — long-season crops need about 90 days of runway, quick greens only 30. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
Documented around Clarkson Valley
Survey cells within 31 miles of Clarkson Valley checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 252 miles off. What to watch for.
What's on the federal record near Clarkson Valley
Closest first, within ~10 miles of Clarkson Valley. Listing isn't leaking, and distance isn't exposure.
- FOREST HILLS COUNTRY CLUBUnderground Storage Tanks · 2400 ft
- MARQUETTE HIGH SCHOOLBrownfields · 0.7 mi
- CVS PHARMACY #18036Brownfields · 0.7 mi
- TOM CAFFRAY SVCBrownfields · 0.9 mi
- T45N R04E 28BCC1Nitrate · 1.0 mi
- T45N R04E 21AAC1Nitrate · 1.2 mi
- CITICORP MORGAGE INCUnderground Storage Tanks · 1.4 mi
- ROCKWOOD SCHOOL DISTRICT GROUNDS BLDGBrownfields · 1.4 mi
- WALGREENS #11744Brownfields · 1.5 mi
- CLEANING PLUS-CLEANING PLUSBrownfields · 1.6 mi
- JAMPLASTToxics Release Inventory · 1.7 mi
- PETCO #1636Brownfields · 1.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Clarkson Valley'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 Clarkson Valley.
Sources Checked
within ~10 miles of Clarkson Valley
Severity Distribution
within ~10 miles of Clarkson Valley
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.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Clarkson Valley
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 Clarkson Valley average
Your land is one point inside Clarkson Valley
Everything above resolves to Clarkson Valley as a whole — one PHZM band and one 28°F frost record, read across 2K 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 Clarkson Valley Average
Clarkson Valley Average
- ●USDA Zones 7a, averaged across Clarkson Valley
- ●One soil character for all of Clarkson Valley
- ●Frost dates read at Clarkson Valley's scale: Mar 22 to Nov 17
YOUR Parcel
- ✓Your exact zone, not Clarkson Valley's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Clarkson Valley
Pull a site-specific report for your exact address in Clarkson Valley, Missouri — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Clarkson Valley averages can't show:
We read public map data around Clarkson Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Clarkson Valley average
How we know this about Clarkson Valley
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 Clarkson Valley’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 Clarkson Valley
When does frost risk typically end in Clarkson Valley?
The last hard freeze (28°F) in Clarkson Valley typically lands around Mar 22, 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 12.
When is the first frost in Clarkson Valley?
The first hard freeze (28°F) in Clarkson Valley typically arrives around Nov 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 3, so the watching starts about Oct 18 — about 240 days after the spring freeze cleared.
How long is the growing season in Clarkson Valley?
Measured between 28°F hard freezes, Clarkson Valley sees about 240 frost-free days — roughly Mar 22 through Nov 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 12 to Nov 3, about 205 days.
Is the soil safe to grow vegetables in Clarkson Valley?
The federal record around Clarkson Valley runs heavier than most — 1,191 documented sites, mostly Underground Storage Tanks entries (468), the nearest Underground Storage Tanks record about 0.5 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do I protect my plants from frost in Clarkson Valley?
From about Oct 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 Nov 17 (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 Nov 17. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Clarkson Valley's scale — its 7a band and its 240-day season. Your yard writes its own version of Clarkson Valley'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 Clarkson Valley’s own scale
7 of the readings below were taken at Clarkson Valley's own scale — its own ~240-day season between 28°F freezes, the 1,725 acres it covers and 1,191 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Clarkson Valley's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Clarkson Valley's own 28°F hard-freeze dates, about Mar 22 and Nov 17 and the ~240-day span between themNOAA 1991–2020 Climate Normals
- 1,191 documented contamination sites on the federal record near Clarkson Valley, the closest Underground Storage Tanks record about 0.5 miles out from the town centreFederal environmental registers
- Clarkson Valley's boundary and the 1,725 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~240-day seasonGrowable Ground crop-matching engine
- The ecoregion at Clarkson Valley's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
- Lanternfly survey cells around Clarkson Valley checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Clarkson Valley's 1,725 acres read through its county's SSURGO summaryfrom St. Louis County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom St. Louis County
- The growing challenges every Missouri grower plans around — written at state scale, so they stay on the state guidefrom Missouri
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom St. Louis County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Clarkson Valley's 1,725 acreswhy one lot differs from the next →
- Which side of Clarkson Valley you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,725 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.5 miles 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 Clarkson Valley-wide figureread your own land →
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