The Midcoast Maine spans USDA hardiness zones 5b-6a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Maine's rocky-peninsula coast, where the Atlantic tempers winters into USDA zones 5b–6a and stretches the frost-free season to roughly 186–222 days — Knox County's 222-day window is the longest of any county in the state. These conditions suit potato, kale, blueberry, and apple — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
The Midcoast Maine spans Maine.
Your yard isn't all of the Midcoast Maine.
The Midcoast Maine spans USDA zones 5b-6a, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. 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 Midcoast Maine — soil, climate, flood, and parcel records. How we handle your address.
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The Midcoast Maine — the short answer
The Midcoast Maine: USDA zones 5b-6a, 186–222 frost-free days depending where in it you stand, in Maine.
- USDA zones
- 5b-6a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 186 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Sagadahoc County
- Counties
- 4
- US Census TIGER/Line 2025
- Region type
- County cluster
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. The season figure is this region's own record, measured across its 4 member counties, not a state or national average.
Hardiness Zone Range
The Midcoast Maine is not one growing season
One answer for the Midcoast Maine averages 4 counties whose growing seasons are 36 days apart — from 186 frost-free days in Sagadahoc County to 222 in Knox County. That is the same region, measured the same way, in the same years. Which end of it your land sits nearer decides what finishes before the first hard freeze.
The middle half of 4 counties runs 190–206 days, with a median of 196 days — a 36-day span end to end.
Measured across 4 member counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020. A member with no own record is absent from the range rather than counted as zero — nothing here is interpolated to the region. Your own site sits somewhere inside this range; a parcel report resolves where.
Where the line runs inside the Midcoast Maine
The middle half of the Midcoast Maine runs 190–206 frost-free days, and 2 of its 4 counties sit outside that — 1 on the short side, 1 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 190 frost-free days
1 county
- Sagadahoc County · 186 days
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
190–206 frost-free days
2 counties
0 of 2 shown
The middle half of the region, and the part a single regional season describes well.
Over 206 frost-free days
1 county
- Knox County · 222 days
Long enough for a second succession of a quick crop after the first comes out.
Each county is placed by its OWN 28°F frost-free normal (NOAA Regional Climate Centers ACIS, 1991-2020), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a site within its county as well — which is the part only your address resolves.
What Grows in the Midcoast Maine
Plants matched to the Midcoast Maine's USDA zones 5b-6a, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Midcoast Maine
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Midcoast Maine’s USDA zones 5b-6a — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Midcoast Maine
The USDA soil survey maps this ground county by county. These are those records weighted by land area across four member counties — this region’s own profile, not a state figure.
The ground is predominantly Spodosols, at 65% of mapped acres, followed by Inceptisols (29%), Histosols (5%) and Entisols (1%). The most extensive named soils are Peru, Lyman, and Boothbay.
25% of those acres are somewhat excessively drained, and another 20% moderately well drained, 14% well drained. Topsoil pH runs 4.2–5.5 between the lowest and the highest county on record. 7% of the footprint is classed prime farmland.
Soil order
Spodosols
Drainage
Somewhat excessively drained
Topsoil pH
4.2–5.5
Hydric soils
23%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Knox County holds the most wetland ground here, at 25% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Midcoast Maine
The soil survey reads this ground county by county, and the readings above are those records summed across the Midcoast Maine. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records25% of the mapped acres across the Midcoast Maine are somewhat excessively drained — ground that drains quickly. That is area-weighted across all four of its mapped counties.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Midcoast Maine runs pH 4.2–5.5 — acidic in all four of them.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Wet ground
From county recordsAbout 23% of the ground across the Midcoast Maine is mapped as hydric — wetland — soil. Knox County carries the most, at 25%.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across the Midcoast Maine — and how to grow with it.
Across the Midcoast Maine's 4 counties the federal record holds 919 documented sites, mostly Underground Storage Tanks (579), Brownfields (200) and Nitrate (54). The heaviest single county is Knox County, with 292.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Midcoast Maine to see which records sit where you actually grow.
Sources Checked
Summed across the 4 counties in the Midcoast Maine
A note from Gnorman
What an experienced grower watches for around here
In and around the Midcoast Maine, Underground Storage Tanks runs higher than the national average — 579 sites across the 4 counties in the Midcoast Maine. That's not a problem with your land — it's information about it.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Midcoast Maine
Everything above resolves to the Midcoast Maine as a whole — a footprint whose own counties record seasons 36 days apart, and hardiness across zones 5b-6a. Your parcel sits at one point in that range, not in the middle of it. 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 region 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 regional average.
Your Lot vs the Midcoast Maine Average
Midcoast Maine Average
- ●USDA Zones 5b-6a, averaged across Midcoast Maine
- ●One soil character for all of Midcoast Maine
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Midcoast Maine's 5b-6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Midcoast Maine
Pull a site-specific report for your exact address in the Midcoast Maine — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Midcoast Maine averages can't show:
We read public map data around The Midcoast Maine — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Midcoast Maine average
How we know this about the Midcoast Maine
The boundary: a cluster of neighboring counties. Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Midcoast Maine
What hardiness zone is the Midcoast Maine?
The Midcoast Maine spans USDA hardiness zones 5b-6a, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Midcoast Maine?
Measured between 28°F hard freezes, the Midcoast Maine's counties mostly run 190 to 206 frost-free days, median 196 (NOAA Regional Climate Centers ACIS, 1991–2020, over 4 member counties). That 16-day spread is the honest read — no single season describes 4 counties, and each county guide below carries its own.
When does frost risk end in the Midcoast Maine?
Across the Midcoast Maine, the middle half of member counties see their last 28°F hard freeze between Apr 12 and Apr 17 (median Apr 15), and their first fall freeze between Oct 24 and Nov 4. Those are hard freezes, not the last light frost: tender transplants wait for about May 6, and elevation decides which end of a 5-day spread you garden in.
What grows well in the Midcoast Maine?
The Midcoast Maine's conditions suit plants such as Potato, Kale, Blueberry, Apple, White Pine. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Midcoast Maine defined?
The Midcoast Maine is defined here as a curated cluster of 4 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Midcoast Maine cover?
The Midcoast Maine spans Maine. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Casco Bay / Greater Portland, Down East Maine, Western Maine Mountains (High Peaks / Rangeley Lakes), Aroostook County, Greater Bangor / Penobscot Valley, and Kennebec Valley (Central Maine) share at least one state with the Midcoast Maine. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Midcoast Maine’s own scale
6 of the readings below were taken at the Midcoast Maine's own scale — the zone 5b-6a band across its footprint, a median 196-day season across its 4 counties and 919 documented federal contamination records across its 4 counties, 292 of them in Knox County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 5b-6a aggregated across all 4 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 4 counties this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 4 counties run 190 to 206 frost-free days, median 196NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 919 documented federal contamination records across its 4 counties, 292 of them in Knox County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 65% Spodosols, topsoil pH 4.2–5.5, area-weighted across its 4 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 5b-6afrom Maine
What this page can’t tell you
- Which end of the 16-day range your ground sits at — 190 days at one extreme, 206 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Midcoast Maine
State growing guides
Counties in this region
Other growing regions across Maine
Coastal southern Maine around Portland and Casco Bay — the three counties of the Census Portland-South Portland metro (Cumberland, Sagadahoc, York) all share USDA hardiness zone 5b and a growing season of roughly 166 to 188 frost-free days, the ocean holding the first fall freeze off until late October.
Down East Maine spans Hancock and Washington counties along the state's easternmost coast, where a maritime-tempered USDA zone 5b holds a short frost-free season of roughly 178 to 188 days.
The only true mountain regime in Maine. Franklin County runs just a 143-day growing season in zone 4b — the coldest, shortest-season part of the state outside Aroostook — because high elevation plus valley cold-air pooling in the High Peaks and Rangeley Lakes country pushes last frosts into late May and first frosts into early September. That is a short, sharp mountain season that neither Maine's milder coast nor Aroostook's flat lowland potato country shares, and it changes what you can start from seed, when you transplant, and which long-season crops need a head start indoors.
Northern Maine's vast potato country — hard winters, a short intense summer, and deep glacial loams behind one of the country's great seed-potato regions.
The Penobscot Valley's settled corridor — Bangor to Old Town river ground whose measured 177-187-day seasons run a solid week past the 2-million-acre northern-forest county around it.
Central Maine's inland exception to an all-coastal map. Where the Kennebec River threads Augusta, Waterville and Gardiner, the corridor holds Zone 5b with roughly 190 frost-free days — one of the warmer pockets of Maine's continental interior, and warmer than the 4b uplands that ring it. But "continental" is the operative word: with no Atlantic moderation like a Casco Bay parcel gets, growers here trade steadier summer heat for harder radiational-frost nights that can fall well below the nominal-zone number on a clear, still spring or fall evening. Read your own cold pockets off the river — not just the corridor's headline zone.