South Portland, Maine, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Growers here do well with cabbage, hazelnut, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in South 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 South 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 South Portland — soil, climate, flood, and parcel records. How we handle your address.
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South Portland — the short answer
South Portland, Maine: USDA zone 6a, about 201 days between hard freezes, across 8K acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 11
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 29
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~201
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 8K 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 South Portland's average, not your lot's — a low corner or a tree line moves it. Against South Portland's 201-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in South Portland
Each reading below is measured for South Portland itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSouth Portland runs about 201 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
MeasuredSouth Portland 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 South Portland is in
South Portland sits in the Northeastern Coastal Zone — EPA Level III, inside the wider Eastern Temperate Forests. That is read at South Portland's own centroid rather than borrowed from Cumberland County.
What Grows in South Portland
Every plant below cleared South Portland's own zone 6a and its 201-day season. Each card opens that plant's Maine profile. How we score.
Is it too late to plant in South Portland?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 14; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 11 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 29 — 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 South Portland
Survey cells within 31 miles of South Portland checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 56 miles off. What to watch for.
What's on the federal record near South Portland
Closest first, within ~10 miles of South Portland. Listing isn't leaking, and distance isn't exposure.
- CARON & WALTZ COMPANYUnderground Storage Tanks · 850 ft
- WAMCO, LLCUnderground Storage Tanks · 1000 ft
- FOREST CITY CEMETERYUnderground Storage Tanks · 1200 ft
- HANDYMAN EQUIP RENTAL CO INCUnderground Storage Tanks · 1300 ft
- GETTY PROP 28221Underground Storage Tanks · 1300 ft
- AUTOZONE #3213Brownfields · 1400 ft
- GLOBAL PETROLEUM TERMINALToxics Release Inventory · 1400 ft
- GLOBAL PETROLEUM TERMINALBrownfields · 1400 ft
- OLSEN, FREDRICK JUnderground Storage Tanks · 1400 ft
- SOUTH PORTLAND TERMINALUnderground Storage Tanks · 1600 ft
- WALGREENS 19678Brownfields · 1600 ft
- ENPRO SERVICES OF MAINE INCBrownfields · 1700 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from South 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 South Portland.
Total Sites
1,033
within ~10 miles of South Portland
Risk Level
Elevated
Highest-severity
16 Superfund sites
Sources Checked
within ~10 miles of South Portland
Severity Distribution
within ~10 miles of South Portland
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around South Portland, Superfund runs higher than the national average — 16 sites within ~10 miles of South Portland. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in South 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 South Portland average
Your land is one point inside South Portland
Everything above resolves to South Portland as a whole — one PHZM band and one 28°F frost record, read across 8K 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 South Portland Average
South Portland Average
- ●USDA Zones 6a, averaged across South Portland
- ●One soil character for all of South Portland
- ●Frost dates read at South Portland's scale: Apr 11 to Oct 29
YOUR Parcel
- ✓Your exact zone, not South Portland's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in South Portland
Pull a site-specific report for your exact address in South Portland, Maine — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that South Portland averages can't show:
We read public map data around South Portland — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the South Portland average
How we know this about South Portland
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 South 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 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 South Portland
When does frost risk typically end in South Portland?
The last hard freeze (28°F) in South Portland typically lands around Apr 11, 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 2.
When is the first frost in South Portland?
The first hard freeze (28°F) in South Portland typically arrives around Oct 29, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 15, so the watching starts about Sep 29 — about 201 days after the spring freeze cleared.
How long is the growing season in South Portland?
Measured between 28°F hard freezes, South Portland sees about 201 frost-free days — roughly Apr 11 through Oct 29, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 2 to Oct 15, about 166 days.
Is the soil safe to grow vegetables in South Portland?
The federal record around South Portland is a meaningful one — 1,033 documented sites, mostly Underground Storage Tanks entries (543), the nearest Underground Storage Tanks record about 0.2 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 South Portland?
From about Sep 29 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 29 (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 29. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at South Portland's scale — its 6a band and its 201-day season. Your yard writes its own version of South 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 South Portland’s own scale
7 of the readings below were taken at South Portland's own scale — its own ~201-day season between 28°F freezes, the 7,709 acres it covers and 1,033 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- South Portland's own USDA hardiness band, zones 6aUSDA PHZM 2023
- South Portland's own 28°F hard-freeze dates, about Apr 11 and Oct 29 and the ~201-day span between themNOAA 1991–2020 Climate Normals
- 1,033 documented contamination sites on the federal record near South Portland, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- South Portland's boundary and the 7,709 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~201-day seasonGrowable Ground crop-matching engine
- The ecoregion at South Portland's own centroid, the Northeastern Coastal ZoneUS EPA Level III Ecoregions
- Lanternfly survey cells around South Portland 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 South Portland's 7,709 acres read through its county's SSURGO summaryfrom Cumberland County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Cumberland County
- The growing challenges every Maine grower plans around — written at state scale, so they stay on the state guidefrom Maine
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Cumberland County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among South Portland's 7,709 acreswhy one lot differs from the next →
- Which side of South 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 7,709 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 South Portland-wide figureread your own land →
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