Northglenn, Colorado, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
The conditions favor cabbage, hazelnut, lavender, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Northglenn, 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 Northglenn 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 Northglenn — soil, climate, flood, and parcel records. How we handle your address.
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Northglenn — the short answer
Northglenn, Colorado: USDA zone 6a, about 183 days between hard freezes, across 5K acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~183
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 5K 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 6a is Northglenn's average, not your lot's — a low corner or a tree line moves it. Against Northglenn's 183-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Northglenn
Each reading below is measured for Northglenn itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredNorthglenn 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
MeasuredNorthglenn sits in USDA hardiness zone 6a.
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 Northglenn is in
Northglenn sits in the High Plains — EPA Level III, inside the wider Great Plains. That is read at Northglenn's own centroid rather than borrowed from Adams County.
What Grows in Northglenn
Every plant below cleared Northglenn's own zone 6a and its 183-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Northglenn?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 22; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 19 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 19 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
What's on the federal record near Northglenn
Closest first, within ~10 miles of Northglenn. Listing isn't leaking, and distance isn't exposure.
- PETCO STORE #920Brownfields · 900 ft
- SAFEWAY 881Brownfields · 900 ft
- GENERAL PARTS DISTRIBUTION LLC DBA CARQUEST AUTO PARTS #3918Brownfields · 1100 ft
- SCL-HEALTH SAINT JOSEPH EMERGENCY DEPARTMENT-NORTHGLENNBrownfields · 1200 ft
- NORTHGLENN ENDOSCOPY CENTER LLCBrownfields · 1200 ft
- SCL HEALTH COMMUNITY HOSPITAL - NORTHGLENNBrownfields · 1200 ft
- CRASH CHAMPIONS LLCBrownfields · 1300 ft
- ECONO LUBE N TUNE #226Brownfields · 1300 ft
- Gasamat #102Underground Storage Tanks · 1300 ft
- CST Metro LLC DBA Corner Store #1139Underground Storage Tanks · 1300 ft
- Pit Stop ConocoUnderground Storage Tanks · 1400 ft
- My Goods Market #6533Underground Storage Tanks · 1400 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Northglenn'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 Northglenn.
Sources Checked
within ~10 miles of Northglenn
Severity Distribution
within ~10 miles of Northglenn
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Northglenn, Toxics Release Inventory runs higher than the national average — 171 sites within ~10 miles of Northglenn. That's not a problem with your land — it's information about it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Northglenn
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 Northglenn average
Your land is one point inside Northglenn
Everything above resolves to Northglenn as a whole — one PHZM band and one 28°F frost record, read across 5K 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 Northglenn Average
Northglenn Average
- ●USDA Zones 6a, averaged across Northglenn
- ●One soil character for all of Northglenn
- ●Frost dates read at Northglenn's scale: Apr 19 to Oct 19
YOUR Parcel
- ✓Your exact zone, not Northglenn's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Northglenn
Pull a site-specific report for your exact address in Northglenn, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Northglenn averages can't show:
We read public map data around Northglenn — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Northglenn average
How we know this about Northglenn
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 Northglenn’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 Northglenn
When does frost risk typically end in Northglenn?
The last hard freeze (28°F) in Northglenn typically lands around Apr 19, 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 10.
When is the first frost in Northglenn?
The first hard freeze (28°F) in Northglenn typically arrives around Oct 19, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 5, so the watching starts about Sep 19 — about 183 days after the spring freeze cleared.
How long is the growing season in Northglenn?
Measured between 28°F hard freezes, Northglenn sees about 183 frost-free days — roughly Apr 19 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 10 to Oct 5, about 148 days.
Is the soil safe to grow vegetables in Northglenn?
The federal record around Northglenn runs heavier than most — 2,622 documented sites, mostly Underground Storage Tanks entries (1,304), the nearest Brownfields record about 0.2 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 Northglenn?
From about Sep 19 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 19 (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 19. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Northglenn's scale — its 6a band and its 183-day season. Your yard writes its own version of Northglenn'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 Northglenn’s own scale
6 of the readings below were taken at Northglenn's own scale — its own ~183-day season between 28°F freezes, the 4,710 acres it covers and 2,622 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Northglenn's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Northglenn's own 28°F hard-freeze dates, about Apr 19 and Oct 19 and the ~183-day span between themNOAA 1991–2020 Climate Normals
- 2,622 documented contamination sites on the federal record near Northglenn, the closest Brownfields record about 0.2 miles out from the town centreFederal environmental registers
- Northglenn's boundary and the 4,710 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 ecoregion at Northglenn's own centroid, the High PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Northglenn's 4,710 acres read through its county's SSURGO summaryfrom Adams County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Adams County
- The growing challenges every Colorado grower plans around — written at state scale, so they stay on the state guidefrom Colorado
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Adams County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Northglenn's 4,710 acreswhy one lot differs from the next →
- Which side of Northglenn you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 4,710 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.2 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 Northglenn-wide figureread your own land →