Yes — Strong Match
viola is grown as an annual, so season length decides it here, not a winter zone — and North Dakota's typical season runs ~157 frost-free days against the ~70 viola needs.
Sow by about Jul 28
Viola is grown as an annual, so what decides it here is season length, not a winter zone. It needs about 70 days from sowing to finish and a typical North Dakota season runs ~157 frost-free days, leaving 87 days of slack. That is room to sow as late as about Jul 28 and still finish before the usual first freeze (Oct 6).
Want more weeks at either end of that window? How to buy the weeks →
70 days to maturity against North Dakota’s ~157-day season. NOAA Regional Climate Centers ACIS 1991-2020 (28°F killing freeze), state median across counties, via stateClimateData.ts.
Your yard isn't the whole zone.
Viola is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical North Dakota site runs ~157 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 viola against your land's actual frost dates, sun, and soil.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Zone Comparison
Viola Needs
- USDA Zones: Data pending
- Sun: Part Sun
- Mature size: 9 in tall
- Picking window: ~90 days of harvest
- Drought tolerance: Low
North Dakota Has
- USDA Zones: 3b-4b
- Last Hard Freeze (28°F): Apr 30 - May 6
- First Hard Freeze (28°F): Oct 4 - Oct 9
- Annual Rainfall: 14-22 inches
- Common Soils: Prairie loam, Clay (Red River Valley), Sandy loam
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 Viola in North Dakota
The frost window
Across North Dakota, the last spring hard freeze (28°F) clears between Apr 30 and May 6, and the first fall hard freeze lands between Oct 4 and Oct 9 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 151-day window you can count on — up to 162 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.
When to start the seed
Those dates are when viola goes out, not when it starts. It is sown under cover about 10 weeks ahead, so counting back from North Dakota's late-side last freeze of May 6 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Days to maturity vs. the window
At 70 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 81 days to spare even in North Dakota'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
Days to maturity
Viola matures in ~70 days (Growable Ground Plant Database). A typical North Dakota site has ~157 frost-free days, so plenty of room for a second succession.
Growing degree days
Viola needs ~600 GDD (base 50°F) to ripen. The state median runs ~1913 GDD (from PRISM 1991-2020 climate normals), so North Dakota'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
Viola likes near-neutral soil (pH 5.4-6.5). That's the common-ground band across North Dakota's prairie loam and clay (red river valley) — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 5.4 and 5.8 — worth knowing before you decide whether a North Dakota soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your North Dakota site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
North Dakota soil pH runs about 7.0–7.5, and that sits above viola's tolerated 5.4–6.5, so the typical North Dakota parcel needs sulfur to bring it down. SSURGO maps it swinging by full points parcel to parcel, so your map unit, not the state number, decides whether viola needs lime or sulfur.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. North Dakota soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Viola in North Dakota — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: Data pending (USDA PLANTS Database)
- State Zones: 3b-4b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 30 - May 6 to Oct 4 - Oct 9 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 70 days
What Else to Consider for Viola in North Dakota
Zone compatibility tells you about winter cold survival — but North Dakota growers also need to think about:
Extreme cold (-40F) and short growing season
Persistent wind desiccates plants
Low rainfall in western ND
Growing viola here specifically
Viola does best acidic (pH 5.4–6.5); North Dakota soils average near pH 7.2, alkaline enough to yellow its leaves as micronutrients lock away.
Work in elemental sulfur or acidic organic matter to pull your parcel toward pH 5.4–6.5, then retest. How to handle it →
What to actually do about these — and the constraints that apply to every North Dakota grower, not just viola — is covered on the North Dakota growing guide.
Timing shifts within North Dakota
Viola needs about 70 days of frost-free season from planting to harvest. Even Bottineau County — North Dakota’s shortest season at 141 frost-free days — clears that by 71 days, so season length isn’t the constraint anywhere in North Dakota. What varies is your own parcel.
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"). Viola's 70-day requirement: USDA PLANTS / Growable Ground plant database (days to maturity). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Viola draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, viola can only work that bloom inside North Dakota's frost window — roughly 157 days, opening after the last 28°F freeze (Apr 30 - May 6) and closing at the first (Oct 4 - Oct 9), per NOAA Regional Climate Centers ACIS, 1991-2020.
Recommended Viola Varieties for North Dakota
North Dakota publishes no state variety trial for viola, so we won't invent a "best for North Dakota" list. Choose types rated to your USDA hardiness zone (3b-4b), and confirm winter survival and drainage against your own parcel.
North Dakota Cooperative Extension
For North Dakota-specific cultivar recommendations, planting calendars, and pest pressure for viola, the canonical source is NDSU Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Viola native to North Dakota?
No — the USDA PLANTS Database lists Viola as introduced rather than native in the Lower 48, so it is not part of North Dakota's native flora. It grows here as a garden plant; pairing it with a few North Dakota natives keeps local pollinators fed too.
Looking for plants that belong here? The North Dakota 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 Viola in North Dakota
When can I plant Viola in North Dakota?
North Dakota's last spring hard freeze (28°F) clears between Apr 30 and May 6, and the first fall hard freeze lands between Oct 4 and Oct 9 (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 Viola mature before first frost in North Dakota?
Yes — Viola matures in 70 days (USDA PLANTS Database), and North Dakota's dependable hard-freeze-free window runs 151 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 81 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 Viola grown in across North Dakota?
North Dakota spans USDA hardiness zones 3b-4b (USDA ARS PHZM 2023). Viola carries a range of zones Data pending, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical North Dakota site have?
A typical North Dakota site sees ~157 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Viola 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.
Is Viola native to North Dakota?
No — the USDA PLANTS Database lists Viola as introduced rather than native in the Lower 48, so it is not part of North Dakota's native flora. It grows here as a garden plant; pairing it with a few North Dakota natives keeps local pollinators fed too.
How should I amend the soil for Viola in North Dakota?
Viola prefers pH 5.4-6.5 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across North Dakota soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Viola actually grow on my specific land in North Dakota?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores viola 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 North Dakota
State-level data is a sketch. Your Growable Ground report scores viola against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that North Dakota viola averages can't show:
We read public map data around North Dakota — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the North Dakota viola average
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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