Generally — Most Areas
mustard cover crop is grown in zones 3-10, and zones 3-9 of Alaska (1a-9a) are in range — most of the state, with the rest the exception.
Mustard Cover Crop in Alaska — the short answer
Mustard Cover Crop in Alaska: grown in zones 3–10, full sun, against a state median of ~147 frost-free days.
- Plant zones
- Grown as an annual — see the growing season
- Growing season, not a hardiness zone
- Alaska zones
- 1a-9a
- USDA PHZM 2023
- Frost window
- Apr 16 - May 15 – Sep 24 - Oct 29
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 85 days
- NOAA Regional Climate Centers ACIS station record, 1991-2020, county 28°F killing freeze
- Days to maturity
- 50 days
- Growable Ground Plant Database
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.
Mustard Cover Crop is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Alaska site runs ~147 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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Alaska is not one climate
A single Alaska answer averages 28 counties whose growing seasons are 155 days apart — from 85 frost-free days in Southeast Fairbanks County to 240 in Sitka County. Which end of that your land sits nearer changes what mustard cover crop can finish before the first hard freeze.
The middle half of 28 counties runs 118–196 days, with a median of 145 days — a 155-day span end to end.
Measured across 28 Alaska counties. NOAA Regional Climate Centers ACIS station record, 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 in Alaska Fits Best
Mustard Cover Crop is rated for zones 3–10 — a cold floor USDA puts at -40 to -30°F. Against Alaska’s 30 counties that band holds in 21 of them, and the line runs at Copper River County (zone 3a), the coldest county still inside it.
Inside zones 3–10
21 counties
- Dillingham County · zone 3a-5a
- Kusilvak County · zone 3a-4b
- Kenai Peninsula County · zone 3b-7a
3 of 21 shown
Below the zone 3 floor
9 counties
- Yukon-Koyukuk County · zone 1a-4a
- North Slope County · zone 1b-4a
- Northwest Arctic County · zone 1b-4a
3 of 9 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.
Even within Alaska's zones 1a-9a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for mustard cover crop (USDA PHZM 2023):
Zone Comparison
Mustard Cover Crop Needs
- USDA Zones: 3-10
- Frost-Free Days: 110+
- Sun: Full Sun
- Mature size: 4 ft tallWe haven't confirmed this against a published source yet.
- Drought tolerance: MediumWe haven't confirmed this against a published source yet.
Alaska Has
- USDA Zones: 1a-9a
- Last Hard Freeze (28°F): Apr 16 - May 15
- First Hard Freeze (28°F): Sep 24 - Oct 29
- Annual Rainfall: 10-160 inches
- Common Soils: Permafrost, Glacial silt, Volcanic ash
Plant Zone Range (zones 3-10)
Preferred Soil pH
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 Mustard Cover Crop in Alaska
The frost window
Across Alaska, the last spring hard freeze (28°F) clears between Apr 16 and May 15, and the first fall hard freeze lands between Sep 24 and Oct 29 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 132-day window you can count on — up to 196 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 hardiness
Mustard Cover Crop takes cold down to about 25°F before a freeze kills it, so you can plant on the early side of Alaska's window — even a few weeks before the final hard freeze. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you. We haven't confirmed this against a published source yet.
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 — Alaska'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 (Growable Ground Plant Database), counting from the last hard freeze it ripens with 82 days to spare even in Alaska's tightest freeze scenario — room for a later start or a second sowing.
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.
Growing Season Fit
Mustard Cover Crop is grown in zones 3–10, which covers part of Alaska (1a-9a), not all of it. It is grown as a summer crop, so season length decides it here. Alaska's typical season runs ~147 frost-free days against the ~110 mustard cover crop needs.
Frost-free days
Mustard Cover Crop wants 110+ frost-free days; a typical Alaska site sees ~147 (NOAA Regional Climate Centers ACIS station record, 1991-2020). That leaves a workable window — start indoors to bank time.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS station record, 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 Alaska. 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 Alaska soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Alaska site is heavier clay or sits in a low spot, a raised bed lifts the roots above wet ground, or work in compost.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Alaska soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Mustard Cover Crop in Alaska
The zone range tells you where mustard cover crop is grown — but Alaska growers also need to think about:
Extremely short growing season (70-110 frost-free days)
Permafrost prevents deep root growth in many areas
Limited soil development in glacial terrain
What to actually do about these — and the constraints that apply to every Alaska grower, not just mustard cover crop — is covered on the Alaska growing guide.
Timing shifts within Alaska
Mustard Cover Crop needs about 110 days of frost-free season to complete its cycle. 25 of Alaska’s 28 counties give it that outright. The tightest that does is Fairbanks North Star County at 114 frost-free days — 4 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Alaska’s 28 counties the frost-free season runs from 85 days in Southeast Fairbanks County to 240 days in Sitka County — a spread of 155 days, which is why a single statewide planting date misleads. The median Alaska county sees 147 frost-free days, leaving mustard cover crop about 37 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.
Pollinator + Wildlife Value
Mustard Cover Crop draws honeybees and native bees (moderate value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, mustard cover crop can only work that bloom inside Alaska's frost window — roughly 147 days, opening after the last 28°F freeze (Apr 16 - May 15) and closing at the first (Sep 24 - Oct 29), per NOAA Regional Climate Centers ACIS station record, 1991-2020. Pollinator value: We haven't confirmed this against a published source yet.
Alaska Cooperative Extension
For Alaska-specific cultivar recommendations, planting calendars, and pest pressure for mustard cover crop, the canonical source is UAF Cooperative Extension Service. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Mustard Cover Crop native to Alaska?
No — the USDA PLANTS Database lists Mustard Cover Crop as introduced rather than native in the Lower 48, so it is not part of Alaska's native flora. It grows here as a garden plant; pairing it with a few Alaska natives keeps local pollinators fed too.
Looking for plants that belong here? The Alaska growing guide lists plants that USDA PLANTS records growing in Alaska and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.
State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.
Common Questions About Growing Mustard Cover Crop in Alaska
When can I plant Mustard Cover Crop in Alaska?
Alaska's last spring hard freeze (28°F) clears between Apr 16 and May 15, and the first fall hard freeze lands between Sep 24 and Oct 29 (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.
Can Mustard Cover Crop mature before first frost in Alaska?
Yes — Mustard Cover Crop matures in 50 days (Growable Ground Plant Database), and Alaska's dependable hard-freeze-free window runs 132 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 82 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 Alaska?
Alaska spans USDA hardiness zones 1a-9a (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 Alaska site have?
A typical Alaska site sees ~147 frost-free days per year (derived from NOAA Regional Climate Centers ACIS station record, 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.
Is Mustard Cover Crop native to Alaska?
No — the USDA PLANTS Database lists Mustard Cover Crop as introduced rather than native in the Lower 48, so it is not part of Alaska's native flora. It grows here as a garden plant; pairing it with a few Alaska natives keeps local pollinators fed too.
How should I amend the soil for Mustard Cover Crop in Alaska?
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 Alaska site — amend for drainage and organic matter first.
Will Mustard Cover Crop actually grow on my specific land in Alaska?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores mustard cover crop against your address's mapped soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Alaska
State-level data is a sketch. Your Growable Ground report scores mustard cover crop against your land's mapped soil, modelled sun, drainage, and frost data — not zone averages.
Three things about your lot that Alaska mustard cover crop averages can't show:
We read public map data around Alaska — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Alaska mustard cover crop average
Explore More
Growing guides for mustard cover crop
Explore Alaska county by county
Alaska carries 30 counties with their own USDA zone — a sample of the growing pages for mustard cover crop there:
Where else mustard cover crop grows
Mustard Cover Crop's zone band crosses state lines — these are the states closest to Alaska 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 Alaska
Alaska has a growing page for 1,011 plants — a rotating sample of the rest of the shelf.
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