Portland, Colorado, sits in USDA hardiness zone 6a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect cabbage, blackberry, california poppy, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Portland, 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 Portland 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 Portland — soil, climate, flood, and parcel records. How we handle your address.
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Portland — the short answer
Portland, Colorado: USDA zone 6a, about 135 days between hard freezes, across 2K acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 30
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~135
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town 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 6a is Portland's average, not your lot's — a low corner or a tree line moves it. Against Portland's 135-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Portland
Each reading below is measured for Portland itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPortland runs about 135 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredPortland 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 Portland is in
Portland sits in the Southern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Portland's own centroid rather than borrowed from Ouray County.
What Grows in Portland
Every plant below cleared Portland's own zone 6a and its 135-day season. Each card opens that plant's Colorado profile. How we score.
Is it too late to plant in Portland?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 18 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 30 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
What's on the federal record near Portland
Closest first, within ~10 miles of Portland. Listing isn't leaking, and distance isn't exposure.
- SenioritaMining · 0.8 mi
- SC04400802CBB00Nitrate · 1.2 mi
- News BoyMining · 1.2 mi
- American Lead/Zinc MillMining · 2.4 mi
- UnknownMining · 2.4 mi
- NasbyMining · 2.4 mi
- AMERICAN LEAD AND ZINC MILLSuperfund · 2.4 mi
- NeodeshaMining · 2.4 mi
- Pony Express MineMining · 2.5 mi
- WedgeMining · 2.6 mi
- Bachelor MillMining · 2.7 mi
- Bachelor MineMining · 2.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Portland'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 Portland.
Total Sites
148
within ~10 miles of Portland
Risk Level
High
Highest-severity
3 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Portland
Severity Distribution
within ~10 miles of Portland
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Portland, two things run higher than the national average within ~10 miles of Portland — Mining (103 sites) and Superfund (3 sites). That's not a problem with your land — it's information about it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Portland
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 Portland average
Your land is one point inside Portland
Everything above resolves to Portland 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 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 Portland Average
Portland Average
- ●USDA Zones 6a, averaged across Portland
- ●One soil character for all of Portland
- ●Frost dates read at Portland's scale: May 18 to Sep 30
YOUR Parcel
- ✓Your exact zone, not Portland's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Portland
Pull a site-specific report for your exact address in Portland, Colorado — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Portland averages can't show:
We read public map data around Portland — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Portland average
How we know this about Portland
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 Portland’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 Portland
When does frost risk typically end in Portland?
The last hard freeze (28°F) in Portland typically lands around May 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 Jun 8.
When is the first frost in Portland?
The first hard freeze (28°F) in Portland typically arrives around Sep 30, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 16, so the watching starts about Aug 31 — about 135 days after the spring freeze cleared.
How long is the growing season in Portland?
Measured between 28°F hard freezes, Portland sees about 135 frost-free days — roughly May 18 through Sep 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 8 to Sep 16, about 100 days.
Is the soil safe to grow vegetables in Portland?
The federal record around Portland runs heavier than most — 148 documented sites, mostly Mining entries (103), the nearest Mining record about 0.8 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 gardeners stretch the season in Portland?
With about 135 frost-free days between hard freezes, Portland rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 163 to 191 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 18 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Portland's scale — its 6a band and its 135-day season. Your yard writes its own version of Portland'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 Portland’s own scale
6 of the readings below were taken at Portland's own scale — its own ~135-day season between 28°F freezes, the 2,049 acres it covers and 148 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Portland's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Portland's own 28°F hard-freeze dates, about May 18 and Sep 30 and the ~135-day span between themNOAA 1991–2020 Climate Normals
- 148 documented contamination sites on the federal record near Portland, the closest Mining record about 0.8 miles out from the town centreFederal environmental registers
- Portland's boundary and the 2,049 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~135-day seasonGrowable Ground crop-matching engine
- The ecoregion at Portland's own centroid, the Southern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Portland's 2,049 acres read through its county's SSURGO summaryfrom Ouray County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Ouray 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 Ouray County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Portland's 2,049 acreswhy one lot differs from the next →
- Which side of Portland you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 2,049 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Mining record about 0.8 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 Portland-wide figureread your own land →
More in Colorado
Wider growing context
What grows across ColoradoPortland sits outside our named growing regions, so Colorado as a whole is its closest context here.
Nearby growing guides