Yes — Strong Match
mustard cover crop (zones 3-10) covers every zone Maine contains (3b-7a), so hardiness is not what limits it anywhere in the state.
Your yard isn't the whole zone.
Mustard Cover Crop is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Maine site runs ~182 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score mustard cover crop against your land's actual frost dates, sun, and soil.
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Zone Comparison
Mustard Cover Crop Needs
- USDA Zones: 3-10
- Frost-Free Days: 110+
- Sun: Full Sun
- Mature size: 4 ft tall
- Drought tolerance: Medium
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 3-10)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Mustard Cover Crop 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.
Frost tenderness
Mustard Cover Crop is frost-tender — its listed minimum temperature is 41°F (USDA PLANTS Database) — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does.
When to start the seed
Mustard Cover Crop is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Maine's dates above are the whole calendar for it. That makes the last-freeze date the binding constraint, and a warmer pocket of your own yard is worth more to this crop than it is to a transplanted one.
Days to maturity vs. the window
At 50 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 110 days to spare even in Maine's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Piscataquis County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says mustard cover crop survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Mustard Cover Crop wants 110+ frost-free days; a typical Maine site sees ~182 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Mustard Cover Crop needs ~900 GDD (base 50°F) to ripen. The state median runs ~1450 GDD (from PRISM 1991-2020 climate normals), so Maine's typical season clears that easily.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Mustard Cover Crop tolerates a wide pH range (pH 5.5-8.5) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in Maine. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 6.5 and 7.5 — worth knowing before you decide whether a Maine soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Maine site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Whether mustard cover crop is safe to eat from Maine soil is a block-by-block question, not a town-wide one — 10,103 documented contamination sites mean levels spike on some parcels and not the one next door. Mustard Cover Crop roots to about 19 inches, so it is the top 19 inches under your address that decide what it takes up, so only a test on your address settles it.
Check your parcel → Source: USDA NRCS SSURGO + EPA/state contamination databases.
Plant pH and drainage requirements from USDA PLANTS Database. Maine soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Mustard Cover Crop in Maine — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: 3-10 (USDA PLANTS Database)
- State Zones: 3b-7a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 16 - May 3 to Oct 10 - Oct 24 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 50 days
What Else to Consider for Mustard Cover Crop 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 mustard cover crop here specifically
Mustard Cover Crop grows its edible leaves in the soil itself, so on any of Maine's 10,103 documented contamination sites it can carry up lead you'd then eat.
Keep mustard cover crop in raised beds of screened clean soil and confirm your parcel's lead level before the first crop. How to handle it →
What to actually do about these — and the constraints that apply to every Maine grower, not just mustard cover crop — 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 mustard cover crop to your county's window, not the statewide date.
Mustard Cover Crop needs about 110 days of frost-free season to complete its cycle. Even Franklin County — Maine’s shortest season at 143 frost-free days — clears that by 33 days, so season length isn’t the constraint anywhere in Maine. What varies is your own parcel.
Across Maine’s 16 counties the frost-free season runs from 143 days in Franklin County to 222 days in Knox County — a spread of 79 days, which is why a single statewide planting date misleads. The median Maine county sees 182 frost-free days, leaving mustard cover crop about 72 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Mustard Cover Crop's 110-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Maine Fits Best
Even within Maine's zones 3b-7a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for mustard cover crop (USDA PHZM 2023):
Pollinator + Wildlife Value
Mustard Cover Crop draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, mustard cover crop 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.
Maine Cooperative Extension
For Maine-specific cultivar recommendations, planting calendars, and pest pressure for mustard cover crop, the canonical source is UMaine Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Mustard Cover Crop native to Maine?
No — the USDA PLANTS Database lists Mustard Cover Crop as introduced rather than native in the Lower 48, so it is not part of Maine's native flora. It grows here as a garden plant; pairing it with a few Maine natives keeps local pollinators fed too.
Looking for plants that belong here? The Maine growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Mustard Cover Crop in Maine
When can I plant Mustard Cover Crop 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). Mustard Cover Crop is frost-tender — its listed minimum temperature is 41°F (USDA PLANTS Database) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Mustard Cover Crop mature before first frost in Maine?
Yes — Mustard Cover Crop matures in 50 days (USDA PLANTS Database), and Maine's dependable hard-freeze-free window runs 160 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 110 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Mustard Cover Crop grown in across Maine?
Maine spans USDA hardiness zones 3b-7a (USDA ARS PHZM 2023). Mustard Cover Crop carries a range of zones 3-10, 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). Mustard Cover Crop needs 110+ frost-free days, 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.
Is Mustard Cover Crop native to Maine?
No — the USDA PLANTS Database lists Mustard Cover Crop as introduced rather than native in the Lower 48, so it is not part of Maine's native flora. It grows here as a garden plant; pairing it with a few Maine natives keeps local pollinators fed too.
How should I amend the soil for Mustard Cover Crop in Maine?
Mustard Cover Crop tolerates pH 5.5-8.5 and well (dry spells) drainage (FAO ECOCROP). That is a 3-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Maine site — amend for drainage and organic matter first.
Will Mustard Cover Crop actually grow on my specific land in Maine?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores mustard cover crop 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 mustard cover crop against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Maine mustard cover crop 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 mustard cover crop average
Explore More
Growing guides for mustard cover crop
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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