Cos Cob, Connecticut, 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.
Among the crops suited to this profile: cabbage, hazelnut, california poppy, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Cos Cob, 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 Cos Cob 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 Cos Cob — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Cos Cob — the short answer
Cos Cob, Connecticut: USDA zone 7a, about 243 days between hard freezes, across 1K acres of town.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 24
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~243
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 1K 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 Cos Cob's average, not your lot's — a low corner or a tree line moves it. Against Cos Cob's 243-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Cos Cob
Each reading below is measured for Cos Cob itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCos Cob runs about 243 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
MeasuredCos Cob 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 Cos Cob is in
Cos Cob sits in the Northeastern Coastal Zone — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Cos Cob's own centroid rather than borrowed from Western Connecticut Planning Region.
What Grows in Cos Cob
Every plant below cleared Cos Cob's own zone 7a and its 243-day season. Each card opens that plant's Connecticut profile. How we score.
Is it too late to plant in Cos Cob?
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 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 24 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
Documented around Cos Cob
Spotted lanternfly documented 4 miles from Cos Cob, first recorded 2020. What to watch for.
What's on the federal record near Cos Cob
Closest first, within ~10 miles of Cos Cob. Listing isn't leaking, and distance isn't exposure.
- MONTGOMERY PINETUM (MAINTENANCE SHED)Underground Storage Tanks · 2000 ft
- MIANUS EQUIPMENT GARAGEUnderground Storage Tanks · 2400 ft
- BALDUCCI'S 3603Brownfields · 0.6 mi
- LEMANS 24, INC.Underground Storage Tanks · 0.6 mi
- BUDGET DRY CLEANERSBrownfields · 0.6 mi
- MINUTE MEN CLEANERSBrownfields · 0.6 mi
- PMG #8681Underground Storage Tanks · 0.7 mi
- COS COB GULFBrownfields · 0.7 mi
- MOBILUnderground Storage Tanks · 0.7 mi
- MOBIL OIL CORP SERV STA F0XBrownfields · 0.7 mi
- SHORELINE POOLS, INC.Underground Storage Tanks · 0.7 mi
- RUDY'S LIMOUSINE SERVICE, INC.Underground Storage Tanks · 0.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Cos Cob'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 Cos Cob.
Total Sites
1,296
within ~10 miles of Cos Cob
Risk Level
Elevated
Highest-severity
8 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Cos Cob
Severity Distribution
within ~10 miles of Cos Cob
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Cos Cob, Brownfields runs higher than the national average — 646 sites within ~10 miles of Cos Cob. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in Cos Cob
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 Cos Cob average
Your land is one point inside Cos Cob
Everything above resolves to Cos Cob as a whole — one PHZM band and one 28°F frost record, read across 1K 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 town 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 Cos Cob Average
Cos Cob Average
- ●USDA Zones 7a, averaged across Cos Cob
- ●One soil character for all of Cos Cob
- ●Frost dates read at Cos Cob's scale: Mar 26 to Nov 24
YOUR Parcel
- ✓Your exact zone, not Cos Cob's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Cos Cob
Pull a site-specific report for your exact address in Cos Cob, Connecticut — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Cos Cob averages can't show:
We read public map data around Cos Cob — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Cos Cob average
How we know this about Cos Cob
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Cos Cob’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 town grain anywhere on this page — there is no town-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 Cos Cob
When does frost risk typically end in Cos Cob?
The last hard freeze (28°F) in Cos Cob typically lands around Mar 26, 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 16.
When is the first frost in Cos Cob?
The first hard freeze (28°F) in Cos Cob typically arrives around Nov 24, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 10, so the watching starts about Oct 25 — about 243 days after the spring freeze cleared.
How long is the growing season in Cos Cob?
Measured between 28°F hard freezes, Cos Cob sees about 243 frost-free days — roughly Mar 26 through Nov 24, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 16 to Nov 10, about 208 days.
Is the soil safe to grow vegetables in Cos Cob?
The federal record around Cos Cob is a meaningful one — 1,296 documented sites, mostly Brownfields entries (646), the nearest Underground Storage Tanks record about 0.4 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.
How do I protect my plants from frost in Cos Cob?
From about Oct 25 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 24 (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 24. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Cos Cob's scale — its 7a band and its 243-day season. Your yard writes its own version of Cos Cob'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 Cos Cob’s own scale
7 of the readings below were taken at Cos Cob's own scale — its own ~243-day season between 28°F freezes, the 1,377 acres it covers and 1,296 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Cos Cob's own USDA hardiness band, zones 7aUSDA PHZM 2023
- Cos Cob's own 28°F hard-freeze dates, about Mar 26 and Nov 24 and the ~243-day span between themNOAA 1991–2020 Climate Normals
- 1,296 documented contamination sites on the federal record near Cos Cob, the closest Underground Storage Tanks record about 0.4 miles out from the town centreFederal environmental registers
- Cos Cob's boundary and the 1,377 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~243-day seasonGrowable Ground crop-matching engine
- The ecoregion at Cos Cob's own centroid, the Northeastern Coastal ZoneUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Cos Coblydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Cos Cob's 1,377 acres read through its county's SSURGO summaryfrom Western Connecticut County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Western Connecticut County
- The growing challenges every Connecticut grower plans around — written at state scale, so they stay on the state guidefrom Connecticut
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Western Connecticut County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Cos Cob's 1,377 acreswhy one lot differs from the next →
- Which side of Cos Cob you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,377 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.4 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 Cos Cob-wide figureread your own land →
More in Connecticut
Wider growing context
What grows across ConnecticutCos Cob sits outside our named growing regions, so Connecticut as a whole is its closest context here.
Nearby growing guides