Yes — Strong Match
nigella (zones 2-10) covers every zone Wisconsin contains (3b-6a), so hardiness is not what limits it anywhere in the state.
Your yard isn't the whole zone.
Nigella is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Wisconsin site runs ~173 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 nigella against your land's actual frost dates, sun, and soil.
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Zone Comparison
Nigella Needs
- USDA Zones: 2-10
- Frost-Free Days: 100+
- Sun: Full Sun
- Mature size: 1.8 ft tall
- Picking window: ~60 days of harvest
- Drought tolerance: Medium
Wisconsin Has
- USDA Zones: 3b-6a
- Last Hard Freeze (28°F): Apr 17 - May 2
- First Hard Freeze (28°F): Oct 9 - Oct 21
- Annual Rainfall: 28-34 inches
- Common Soils: Silt loam, Clay loam, Sandy outwash
Plant Zone Range (zones 2-10)
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 Nigella in Wisconsin
The frost window
Across Wisconsin, the last spring hard freeze (28°F) clears between Apr 17 and May 2, and the first fall hard freeze lands between Oct 9 and Oct 21 (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 187 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
Nigella 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
Nigella is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Wisconsin'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 70 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 90 days to spare even in Wisconsin's tightest freeze scenario — room for a later start or a second sowing.
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 nigella survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Nigella wants 100+ frost-free days; a typical Wisconsin site sees ~173 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Nigella needs ~900 GDD (base 50°F) to ripen. The state median runs ~2102 GDD (from PRISM 1991-2020 climate normals), so Wisconsin'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
Nigella likes near-neutral soil (pH 6-8). That's the common-ground band across Wisconsin's silt loam and clay loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6.5 and 7.3 — worth knowing before you decide whether a Wisconsin soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Wisconsin site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH and drainage requirements from USDA PLANTS Database. Wisconsin soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Nigella in Wisconsin — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: 2-10 (USDA PLANTS Database)
- State Zones: 3b-6a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 17 - May 2 to Oct 9 - Oct 21 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 70 days
What Else to Consider for Nigella in Wisconsin
Zone compatibility tells you about winter cold survival — but Wisconsin growers also need to think about:
Cold winters (-30F in northern WI)
Short growing season (110-140 frost-free days)
Sandy central soils drain too quickly
What to actually do about these — and the constraints that apply to every Wisconsin grower, not just nigella — is covered on the Wisconsin growing guide.
Timing shifts within Wisconsin
Nigella needs about 100 days of frost-free season to complete its cycle. Even Florence County — Wisconsin’s shortest season at 140 frost-free days — clears that by 40 days, so season length isn’t the constraint anywhere in Wisconsin. What varies is your own parcel.
Across Wisconsin’s 72 counties the frost-free season runs from 140 days in Florence County to 217 days in Milwaukee County — a spread of 77 days, which is why a single statewide planting date misleads. The median Wisconsin county sees 173 frost-free days, leaving nigella about 73 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"). Nigella's 100-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Wisconsin Fits Best
Even within Wisconsin's zones 3b-6a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for nigella (USDA PHZM 2023):
Pollinator + Wildlife Value
Nigella draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, nigella can only work that bloom inside Wisconsin's frost window — roughly 173 days, opening after the last 28°F freeze (Apr 17 - May 2) and closing at the first (Oct 9 - Oct 21), per NOAA Regional Climate Centers ACIS, 1991-2020.
Wisconsin Cooperative Extension
For Wisconsin-specific cultivar recommendations, planting calendars, and pest pressure for nigella, the canonical source is UW–Madison Division of Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Nigella native to Wisconsin?
No — the USDA PLANTS Database lists Nigella as introduced rather than native in the Lower 48, so it is not part of Wisconsin's native flora. It grows here as a garden plant; pairing it with a few Wisconsin natives keeps local pollinators fed too.
Looking for plants that belong here? The Wisconsin 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 Nigella in Wisconsin
When can I plant Nigella in Wisconsin?
Wisconsin's last spring hard freeze (28°F) clears between Apr 17 and May 2, and the first fall hard freeze lands between Oct 9 and Oct 21 (NOAA Regional Climate Centers ACIS, 1991-2020). Nigella 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 Nigella mature before first frost in Wisconsin?
Yes — Nigella matures in 70 days (USDA PLANTS Database), and Wisconsin's dependable hard-freeze-free window runs 160 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 90 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 Nigella grown in across Wisconsin?
Wisconsin spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Nigella carries a range of zones 2-10, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Wisconsin site have?
A typical Wisconsin site sees ~173 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Nigella needs 100+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Nigella native to Wisconsin?
No — the USDA PLANTS Database lists Nigella as introduced rather than native in the Lower 48, so it is not part of Wisconsin's native flora. It grows here as a garden plant; pairing it with a few Wisconsin natives keeps local pollinators fed too.
How should I amend the soil for Nigella in Wisconsin?
Nigella prefers pH 6-8 and well (dry spells) drainage (FAO ECOCROP). That sits in the common-ground band across Wisconsin soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Nigella actually grow on my specific land in Wisconsin?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores nigella 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 Wisconsin
State-level data is a sketch. Your Growable Ground report scores nigella against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Wisconsin nigella averages can't show:
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