Seward, Alaska, sits in USDA hardiness zone 7a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Crops well matched to these conditions include cabbage, blackberry, california poppy, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Seward, 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 Seward 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 Seward — soil, climate, flood, and parcel records. How we handle your address.
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Seward — the short answer
Seward, Alaska: USDA zone 7a, about 148 days between hard freezes, across 9K acres of city.
- USDA zone
- 7a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 2
- Kenai Peninsula Borough normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Sep 27
- Kenai Peninsula Borough normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~148
- Kenai Peninsula Borough normal — NOAA 1991–2020, nearest to this town
- City area
- 9K 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 Kenai Peninsula Borough’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 7a is Seward's average, not your lot's — a low corner or a tree line moves it. Against Seward's 148-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Seward
Each reading below is measured for Seward itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsSeward runs about 148 days between hard freezes (read from Kenai Peninsula Borough, the closest normal to Seward) — 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
MeasuredSeward 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 Seward
Every plant below cleared Seward's own zone 7a and its 148-day season. Each card opens that plant's Alaska profile. How we score.
Is it too late to plant in Seward?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Apr 4; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 2 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 27 — 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 Seward
Closest first, within ~10 miles of Seward. Listing isn't leaking, and distance isn't exposure.
- HDR MARINE LLCBrownfields · 1.0 mi
- ALASKA LOGISTICS LLCBrownfields · 1.2 mi
- Seward Fisheries Main PlantUnderground Storage Tanks · 1.2 mi
- MARINE SPECIALTIES OF ALASKABrownfields · 1.3 mi
- Seward FisheriesUnderground Storage Tanks · 1.4 mi
- Alaska Vocational Technical CenterUnderground Storage Tanks · 1.4 mi
- RAIBOW FIBERGLASS AND BOAT REPAIR LLCBrownfields · 1.4 mi
- SHORESIDE PETROLEUM SEWARDBrownfields · 1.5 mi
- MEEHAN BY PRODUCTSBrownfields · 1.5 mi
- USARMY FT WAINWRIGHT SEWARD ARMY RECREATION CENTERBrownfields · 1.5 mi
- SB00100134CADA1 001Nitrate · 1.5 mi
- SAFEWAY STORE #2728Brownfields · 1.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Seward'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 Seward.
Total Sites
78
within ~10 miles of Seward
Risk Level
Moderate
Highest-severity
11 mining sites (prospects, none worked)
Sources Checked
within ~10 miles of Seward
Severity Distribution
within ~10 miles of Seward
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Seward, Mining runs higher than the national average — 11 sites within ~10 miles of Seward. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Seward
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 Seward average
Your land is one point inside Seward
Everything above resolves to Seward as a whole — one PHZM band, read across 9K acres, with hard-freeze dates borrowed from Kenai Peninsula Borough’s record because no 30-year normal resolves at this city’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 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 Seward Average
Seward Average
- ●USDA Zones 7a, averaged across Seward
- ●One soil character for all of Seward
- ●Frost dates read at Seward's scale: May 2 to Sep 27
YOUR Parcel
- ✓Your exact zone, not Seward's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Seward
Pull a site-specific report for your exact address in Seward, Alaska — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Seward averages can't show:
We read public map data around Seward — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Seward average
How we know this about Seward
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 Kenai Peninsula 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 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 Seward
When does frost risk typically end in Seward?
The last hard freeze (28°F) in Seward typically lands around May 2, 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 23.
When is the first frost in Seward?
The first hard freeze (28°F) in Seward typically arrives around Sep 27, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 13, so the watching starts about Aug 28 — about 148 days after the spring freeze cleared.
How long is the growing season in Seward?
Measured between 28°F hard freezes, Seward sees about 148 frost-free days — roughly May 2 through Sep 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 23 to Sep 13, about 113 days.
Is the soil safe to grow vegetables in Seward?
The federal record around Seward shows 78 documented sites, mostly Underground Storage Tanks entries (27), the nearest Brownfields record about 1.0 miles out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do gardeners stretch the season in Seward?
With about 148 frost-free days between hard freezes, Seward 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 176 to 204 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 2 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Seward's scale — its 7a band and its 148-day season. Your yard writes its own version of Seward'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 Seward’s own scale
4 of the readings below were taken at Seward's own scale — the 8,934 acres it covers and 78 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Seward's own USDA hardiness band, zones 7aUSDA PHZM 2023
- 78 documented contamination sites on the federal record near Seward, the closest Brownfields record about 1.0 miles out from the town centreFederal environmental registers
- Seward's boundary and the 8,934 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7a and a ~148-day seasonGrowable Ground crop-matching engine
Inherited from a wider read
- The 28°F hard-freeze dates — Seward has no normal of its own, so its county's is the closest measured readfrom Kenai Peninsula Borough
- Soil character — no town-scale survey exists, so Seward's 8,934 acres read through its county's SSURGO summaryfrom Kenai Peninsula County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Kenai Peninsula 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 Kenai Peninsula County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Seward's 8,934 acreswhy one lot differs from the next →
- Which side of Seward you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 8,934 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 1.0 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 Seward-wide figureread your own land →