Petersburg, Alaska, sits in USDA hardiness zone 7a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
These conditions suit cabbage, pawpaw, california poppy, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in Petersburg, 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 Petersburg 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 Petersburg — soil, climate, flood, and parcel records. How we handle your address.
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Petersburg — the short answer
Petersburg, Alaska: USDA zone 7a, about 196 days between hard freezes, across 28K acres of town.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 16
- Petersburg Borough normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Oct 29
- Petersburg Borough normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~196
- Petersburg Borough normal — NOAA 1991–2020, nearest to this town
- Town area
- 28K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Petersburg Borough’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 7a is Petersburg's average, not your lot's — a low corner or a tree line moves it. Against Petersburg's 196-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Petersburg
Each reading below is measured for Petersburg itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsPetersburg runs about 196 days between hard freezes (read from Petersburg Borough, the closest normal to Petersburg) — 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
MeasuredPetersburg 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
What Grows in Petersburg
Every plant below cleared Petersburg's own zone 7a and its 196-day season. Each card opens that plant's Alaska profile. How we score.
Is it too late to plant in Petersburg?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 19; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 16 (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. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
What's on the federal record near Petersburg
Closest first, within ~10 miles of Petersburg. Listing isn't leaking, and distance isn't exposure.
- PETERSBURG CY OF LANDFILL & BALING FCLTYBrownfields · 2.6 mi
- West Wrangle NarrowsMining · 4.0 mi
- USDOT FAA PETERSBURG FACSuperfund · 4.0 mi
- Temsco Helicopters, Inc.Underground Storage Tanks · 4.1 mi
- Kupreanof Flying ServiceUnderground Storage Tanks · 4.1 mi
- LITUYA FREIGHT RUNNERSBrownfields · 4.1 mi
- ALASKA DOT&PFBrownfields · 4.1 mi
- PETERSBURG JAMES A JOHNNSON AIRPORTBrownfields · 4.2 mi
- FAA Duncan CanalUnderground Storage Tanks · 4.4 mi
- Petersburg TerminalUnderground Storage Tanks · 4.4 mi
- FAA Level IslandUnderground Storage Tanks · 4.4 mi
- BOAT R BBrownfields · 4.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Petersburg'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 Petersburg.
Total Sites
32
within ~10 miles of Petersburg
Risk Level
Elevated
Highest-severity
2 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Petersburg
Severity Distribution
within ~10 miles of Petersburg
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.
- •A Superfund listing means federally documented contamination. Test soil and water before planting edibles nearby.
Check your specific parcel in Petersburg
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 Petersburg average
Your land is one point inside Petersburg
Everything above resolves to Petersburg as a whole — one PHZM band, read across 28K acres, with hard-freeze dates borrowed from Petersburg Borough’s record because no 30-year normal resolves at this town’s own centroid. 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 Petersburg Average
Petersburg Average
- ●USDA Zones 7a, averaged across Petersburg
- ●One soil character for all of Petersburg
- ●Frost dates read at Petersburg's scale: Apr 16 to Oct 29
YOUR Parcel
- ✓Your exact zone, not Petersburg's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Petersburg
Pull a site-specific report for your exact address in Petersburg, Alaska — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Petersburg averages can't show:
We read public map data around Petersburg — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Petersburg average
How we know this about Petersburg
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 Petersburg Borough’s record, because none resolves here; 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 Petersburg
When does frost risk typically end in Petersburg?
The last hard freeze (28°F) in Petersburg typically lands around Apr 16, 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 7.
When is the first frost in Petersburg?
The first hard freeze (28°F) in Petersburg 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 196 days after the spring freeze cleared.
How long is the growing season in Petersburg?
Measured between 28°F hard freezes, Petersburg sees about 196 frost-free days — roughly Apr 16 through Oct 29, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 7 to Oct 15, about 161 days.
Is the soil safe to grow vegetables in Petersburg?
The federal record around Petersburg is a meaningful one — 32 documented sites, mostly Underground Storage Tanks entries (15), the nearest Brownfields record about 2.6 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 Petersburg?
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 Petersburg's scale — its 7a band and its 196-day season. Your yard writes its own version of Petersburg'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 Petersburg’s own scale
4 of the readings below were taken at Petersburg's own scale — the 28,273 acres it covers and 32 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Petersburg's own USDA hardiness band, zones 7aUSDA PHZM 2023
- 32 documented contamination sites on the federal record near Petersburg, the closest Brownfields record about 2.6 miles out from the town centreFederal environmental registers
- Petersburg's boundary and the 28,273 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~196-day seasonGrowable Ground crop-matching engine
Inherited from a wider read
- The 28°F hard-freeze dates — Petersburg has no normal of its own, so its county's is the closest measured readfrom Petersburg Borough
- Soil character — no town-scale survey exists, so Petersburg's 28,273 acres read through its county's SSURGO summaryfrom Petersburg County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Petersburg County
- The growing challenges every Alaska grower plans around — written at state scale, so they stay on the state guidefrom Alaska
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Petersburg County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Petersburg's 28,273 acreswhy one lot differs from the next →
- Which side of Petersburg you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 28,273 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 2.6 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 Petersburg-wide figureread your own land →