Unlikely — Zone Mismatch
ranunculus (zones 8-10) does not overlap with Maine's zone range (3b-7a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Ranunculus is hardy to zone 8, and the warmest ground in Maine is zone 6 — 2 zones short. Planted in open ground it will not survive a Maine winter. To grow it here, grow ranunculus in an earth-sheltered greenhouse — its modeled 2.5-zone lift covers this gap.
An earth-sheltered greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 8-10 (plant) against 3-6 (Maine). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['earth_sheltered'] (+2.5 zones) via api/fast_sections.py Unlock Engine v2.
Ranunculus in Maine — the short answer
Ranunculus in Maine: hardy in zones 8–10, part sun, against a state median of ~182 frost-free days.
- Plant zones
- 8-10
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Maine zones
- 3b-7a
- USDA PHZM 2023
- Frost window
- Apr 16 - May 3 – Oct 10 - Oct 24
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 143 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Maine spans zones 3b-7a, but your yard has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score ranunculus against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Maine is not one climate
A single Maine answer averages 16 counties whose growing seasons are 79 days apart — from 143 frost-free days in Franklin County to 222 in Knox County. Which end of that your land sits nearer changes what ranunculus can finish before the first hard freeze.
The middle half of 16 counties runs 154–191 days, with a median of 178 days — a 79-day span end to end.
Measured across 16 Maine counties. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where Ranunculus Stands in Maine
Ranunculus is rated for zones 8–10 — a cold floor USDA puts at 10 to 20°F. No Maine county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Maine winters, not about ranunculus.
Below the zone 8 floor
16 counties
- Aroostook County · zone 4a
- Franklin County · zone 4b
- Piscataquis County · zone 4b
3 of 16 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Zone Comparison
Ranunculus Needs
- USDA Zones: 8-10
- Sun: Part Sun
- Mature size: 1.5 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: Low
Maine Has
- USDA Zones: 3b-7a
- Last Hard Freeze (28°F): Apr 16 - May 3
- First Hard Freeze (28°F): Oct 10 - Oct 24
- Annual Rainfall: 36-50 inches
- Common Soils: Glacial till, Sandy loam, Rocky loam
Plant Zone Range (zones 8-10)
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Ranunculus in Maine
The frost window
Across Maine, the last spring hard freeze (28°F) clears between Apr 16 and May 3, and the first fall hard freeze lands between Oct 10 and Oct 24 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 160-day window you can count on — up to 191 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Timing tuned to sub-state frost dates — Piscataquis County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
What Else to Consider for Ranunculus in Maine
Zone compatibility tells you about winter cold survival — but Maine growers also need to think about:
Very short growing season (100-140 frost-free days)
Rocky glacial soils require significant clearing
Harsh winters with heavy snow and ice
Growing ranunculus here specifically
Ranunculus wilts without steady moisture and rates to zones 8–10; roughly 21.7% of Maine sits on sandy, excessively-drained ground (SSURGO) that sheds water almost as fast as it falls.
Hold moisture for ranunculus with deep mulch and drip lines, especially on the droughtiest parcels. How to handle it →
What to actually do about these — and the constraints that apply to every Maine grower, not just ranunculus — is covered on the Maine growing guide.
Timing shifts within Maine
Maine isn't one climate. In Piscataquis County, the last hard freeze (28°F) holds until about May 15 — roughly 23 days later than the recorded state median — so plant ranunculus to your county's window, not the statewide date.
County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). A parcel report resolves your address's own frost dates.
Where in Maine Ranunculus Is Zone-Hardy
Ranunculus is rated for USDA zones 8–10. No Maine county reaches it. Even Lincoln County, the state’s mildest winter at zone 6a, sits below the plant’s zone 8 floor — so in open ground this one needs winter protection here, or a container that comes under cover.
Across those 16 counties Maine’s winter-low ladder runs from zone 4a in Aroostook County to zone 6a in Lincoln County — 2 USDA zones of spread, which is 20°F between the two counties’ average coldest night of the year. None of that range reaches the band ranunculus needs, so here the statewide answer really is the answer.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. Ranunculus’s zone 8–10 band: USDA PLANTS / Growable Ground plant database. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Ranunculus draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, ranunculus can only work that bloom inside Maine's frost window — roughly 182 days, opening after the last 28°F freeze (Apr 16 - May 3) and closing at the first (Oct 10 - Oct 24), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant Ranunculus
Ranunculus is listed as toxic to dogs, cats (all) at a mild level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Maine this is a one-season plant and the first hard freeze (Oct 10 - Oct 24) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Ranunculus Varieties for Maine
Maine publishes no state variety trial for ranunculus, so we won't invent a "best for Maine" list. Choose types rated to your USDA hardiness zone (3b-7a), and confirm winter survival and drainage against your own parcel.
Maine Cooperative Extension
For Maine-specific cultivar recommendations, planting calendars, and pest pressure for ranunculus, the canonical source is UMaine Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Ranunculus in Maine
When can I plant Ranunculus in Maine?
Maine's last spring hard freeze (28°F) clears between Apr 16 and May 3, and the first fall hard freeze lands between Oct 10 and Oct 24 (NOAA Regional Climate Centers ACIS, 1991-2020). Time outdoor planting to after the last hard freeze for your specific site — a further two to three weeks for anything tender — and count back from those dates for transplant scheduling.
What hardiness zone is Ranunculus grown in across Maine?
Maine spans USDA hardiness zones 3b-7a (USDA ARS PHZM 2023). Ranunculus carries a range of zones 8-10, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Maine site have?
A typical Maine site sees ~182 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Ranunculus should be matched against that window, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Piscataquis, the freeze-free season runs shorter than the state average, so verify your own county's window.
Will Ranunculus actually grow on my specific land in Maine?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores ranunculus against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Maine
State-level data is a sketch. Your Growable Ground report scores ranunculus against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Maine ranunculus averages can't show:
We read public map data around Maine — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Maine ranunculus average
Explore More
Growing guides for ranunculus
Explore Maine county by county
Maine carries 16 counties with their own USDA zone — a sample of the growing pages for ranunculus there:
Where else ranunculus grows
Ranunculus's zone band crosses state lines — these are the states closest to Maine in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Maine
Maine has a growing page for 806 plants — a rotating sample of the rest of the shelf.
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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