Petersburg Borough, in Alaska, sits in USDA hardiness zones 3a-4b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
On paper, cabbage, cranberry, turkish rocket, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Petersburg Borough lies within the Southeast Alaska / Inside Passage Panhandle — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Petersburg Borough holds more than one microclimate.
Soils and elevations shift across Petersburg Borough, so your frost dates and drainage aren't the county average. 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 Borough — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Petersburg Borough — the short answer
Petersburg Borough, Alaska: USDA zones 3a-4b, about 196 days between hard freezes, across 1.9M acres.
- USDA zones
- 3a-4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 16
- PETERSBURG 1 station, 107 ft — 34 km away, 21 yr record
- First hard freeze (28°F)
- Oct 29
- PETERSBURG 1 station, 107 ft — 34 km away, 21 yr record
- Days between freezes
- ~196
- PETERSBURG 1 station, 107 ft — 34 km away, 21 yr record
- County area
- 1.9M acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 3a-4b is Petersburg Borough's average, not your lot's — a low corner or a tree line moves it. Against Petersburg Borough's 196-day season, see what your own ground reads.
Soil in Petersburg County
Detailed USDA soil-survey (SSURGO) mapping is limited across Petersburg County, so there isn't a reliable county-wide soil summary to show here yet — a gap in the national survey, not in the ground itself.
Soil still varies lot by lot — soil types explained.
What this means for growing in Petersburg Borough
Each reading below is measured for Petersburg Borough itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPetersburg Borough runs about 196 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
MeasuredPetersburg Borough sits in USDA hardiness zones 3a-4b.
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 Borough
We scored all 1,086 plants against Petersburg Borough's own USDA zone 3a-4b and its own 196-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Alaska profile.
Is it too late to plant in Petersburg Borough?
For most of the year, no — what changes is which crops still fit the days remaining. 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. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
Safe to Grow Here?
What the federal record shows across Petersburg County — and how to grow with it.
We checked the federal record across Petersburg County — 118 documented sites across 5 of the 9 source types we track.
The most significant on record: 5 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Petersburg Borough carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Petersburg Borough
Closest first, across Petersburg County. Listing isn't leaking, and distance isn't exposure.
- Colp & Lee Gold-Copper-Lead-Zinc ProspectMining · 7.5 mi
- Colp and LeeMining · 7.6 mi
- CascadeMining · 11.6 mi
- Unnamed (on Thomas Bay)Mining · 11.7 mi
- Unnamed Copper-Silver OccurrenceMining · 14.0 mi
- Port Houghton Copper ProspectMining · 14.1 mi
- Louise GroupMining · 15.2 mi
- Admiral GroupMining · 15.8 mi
- Northern Copper CompanyMining · 19.8 mi
- Wastewater Utility Pump Station#4Underground Storage Tanks · 20.1 mi
- Portage MountainMining · 20.2 mi
- Portage Mountain GroupMining · 20.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Petersburg Borough'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 Borough.
Total Sites
118
across Petersburg County
Risk Level
High
Highest-severity
5 Superfund sites (none NPL-listed)
Sources Checked
across Petersburg County
Severity Distribution
across Petersburg County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Petersburg Borough, two things run higher than the national average across Petersburg County — Mining (82 sites) and Superfund (5 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around 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 Petersburg Borough
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 Borough average
Your land is one point inside Petersburg Borough
Everything above resolves to Petersburg Borough as a whole — one PHZM band and one county frost record, read across 1.9M 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 county 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 county average.
Your Lot vs the Petersburg Borough Average
Petersburg Borough Average
- ●USDA Zones 3a-4b, averaged across Petersburg Borough
- ●One soil character for all of Petersburg Borough
- ●Frost dates read at Petersburg Borough's scale: Apr 16 to Oct 29
YOUR Parcel
- ✓Your exact zone, not Petersburg Borough's 3a-4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Petersburg Borough
Pull a site-specific report for your exact address in Petersburg Borough, Alaska — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Petersburg Borough averages can't show:
We read public map data around Petersburg Borough — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Petersburg Borough average
How we know this about Petersburg Borough
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Petersburg Borough carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Petersburg Borough
When does frost risk typically end in Petersburg Borough?
The last hard freeze (28°F) in Petersburg Borough 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.
How long is the growing season in Petersburg Borough?
Measured between 28°F hard freezes, Petersburg Borough 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 Borough?
The federal record around Petersburg Borough runs heavier than most — 118 documented sites, mostly Mining entries (82), the nearest Mining record about 7.5 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.
Everything above is measured at Petersburg Borough's scale — its 3a-4b band and its 196-day season. Your yard writes its own version of Petersburg Borough's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Alaska's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Petersburg Borough’s own scale
5 of the readings below were taken at Petersburg Borough's own scale — its own ~196-day span between 28°F freezes and 118 documented sites inside its boundary; 2 are borrowed from a wider read, named and linked below.
Measured here
- Petersburg Borough's own USDA hardiness band, zones 3a-4bUSDA PHZM 2023
- Petersburg Borough's own 28°F hard-freeze dates and its ~196-day span between themNOAA 1991–2020 Climate Normals
- 118 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Mining record about 7.5 miles outFederal environmental registers
- Petersburg Borough's boundary and the 1,856,568 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 3a-4b and a ~196-day seasonGrowable Ground crop-matching engine
Inherited from a wider read
What this page can’t tell you
- How the season shifts across Petersburg Borough — the ~196 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Petersburg Borough's 1,856,568 acreswhy one lot differs from the next →
- Which of those 118 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Petersburg Boroughread your own land →