Southern Maine primarily falls into USDA plant hardiness zones 5a to 6a, with some small areas reaching as warm as Zone 6b and even 7a in the warmest microclimates off the coast in the Penobscot Bay area.
Here’s what you need to know about southern Maine’s planting zones and what they mean for your backyard decisions.
Planting zone map of southern Maine
Are you interested in learning more about the zones of Maine or other parts of the state? Here are our detailed guides to planting zones in Maine:
Planting zones by city
Biddeford: Hardiness zone 6a
Brunswick: Hardiness zones 5b and 6a
Kennebunkport: Hardiness zone 6a
Kittery: Hardiness zone 6a
Old Orchard Beach: Hardiness zones 6a and 6b
Portland: Hardiness zones 5b, 6a and 6b
Saco: Hardiness zones 5b, 6a and 6b
Sanford: Hardiness zone 5b
Scarborough: Hardiness zones 5b and 6a
South Berwick: Hardiness zones 5b and 6a
South Portland: Hardiness zone 6a
Wells: Hardiness zones 5b and 6a
Westbrook: Hardiness zones 5b and 6a
Windham: Hardiness zone 5b
York: Hardiness zones 6a and 6b
Southern Maine’s planting zones explained
Surely, you might think the concept of observing planting zones is somewhat hocus-pocus. After all, aren’t seeds destined to sprout when you give them soil, water, and a pinch of sunlight? Well…it turns out there’s a little more science to it.
Different plants and crops have varying needs for sunlight, temperature, and rainfall. Plant hardiness zones help in determining which plants would flourish best in certain regions. It can affect the grass seed planting windows and what specific grass types are suitable for your zone.
Note: It’s important to understand that these planting zones are based on the average annual minimum winter temperatures in a given area.
Zone 5a (-20°F to -15°F)
Parts of Oxford County in western Maine fall into Zone 5a. This zone experiences cold winters but is slightly milder than the colder zones further north.
Best grass types:
- Kentucky bluegrass
- Fine fescues
- Tall fescue
- Perennial ryegrass
Shrubs:
- Highbush blueberry
- Lilac
- Hydrangea
- Azalea
- Roses
Perennials:
- Astilbe
- Black-eyed Susans
- Delphinium
- Hollyhock
Trees:
- American elder
- Black cherry
- Common chokecherry
Zone 5b (-15°F to -10°F)
Cities like Sanford, Scarborough, Westbrook, Windham, South Berwick, and Portland fall into Zone 5b. This zone has relatively cold winters but is warmer than Zone 5a.
Best grass types:
- Kentucky bluegrass
- Fine fescues
- Tall fescue
- Perennial ryegrass
Shrubs:
- Butterfly bush
- Forsythia
- Spirea
- Viburnum
- Weigela
Perennials:
- Coneflowers
- Coreopsis
- Phlox
- Rudbeckia
- Sedum
Trees:
- Kousa dogwood
- Japanese maple
- Redbud
Zone 6a (-10°F to -5°F)
Coastal cities and towns like Portland, Biddeford, Saco, Kennebunkport, Kittery, and Old Orchard Beach fall into the milder Zone 6a due to their proximity to the ocean.
Best grass types:
- Kentucky bluegrass
- Fine fescues
- Tall fescue
- Perennial ryegrass
Shrubs:
- Boxwood
- Camellia
- Daphne
- Rhododendron
- Yew
Perennials:
- Ageratum
- Campanula
- Foxglove
- Lavender
- Snapdragon
Trees:
- Birch
- Honey locust
- Linden
- Red maple
- Tulip tree
Zone 6b (-5°F to 0°F)
Some areas right along the coast like parts of Portland, Saco, and York are in the even warmer Zone 6b, experiencing some of the mildest winters in the region.
Best grass types:
- Kentucky bluegrass
- Fine fescues
- Tall fescue
- Perennial ryegrass
Shrubs:
- Winterberry
- Northern Bayberry
- Gray Dogwood
- Ninebark
Perennials:
- Bee balm
- Coneflowers
- Hostas
- Daylilies
Trees:
- Shadbush
- American hornbeam
- Striped maple
- Pagoda dogwood
Zone 7a (0°F to 5°F)
The only location in southern Maine that reaches Zone 7a is Matinicus Island, which benefits from the warming influence of the surrounding ocean waters.
Best grass types:
- Kentucky bluegrass
- Fine fescues
- Tall fescue
- Perennial ryegrass
Shrubs:
- Bigleaf maple
- Atlas cedar
- English holly
- Hydrangea
- Lilac
Perennials:
- Bleeding heart
- Columbine
- Daylily
- Hosta
- Salvia
Trees:
- American holly
- Japanese maple
- Red maple
- River birch
- Weeping willow
Call a lawn care pro for help
Sometimes, the best approach to understanding your planting zone is to consult with a seasoned professional. They have years of experience observing the local weather patterns and soil conditions, which can give them a distinct edge in determining what plants and grass types will thrive and under what circumstances.
We can help you connect with experienced local pros who can provide valuable advice and guidance.
Main Image Credit: John Phelan | Wikimedia Commons | CC BY-SA 3.0
