Bluffton, IN planting calendar
- USDA zone
- 6a−10 to −5 °F
- Last frost
- Apr 24avg, 32°F
- First frost
- Oct 20avg, 32°F
- Growing season
- 179days
Bluffton, Indiana is in USDA plant hardiness zone 6a. Its average last spring frost is around April 24 and the first fall frost around October 20, giving a growing season of about 179 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Bluffton planting calendar
Each crop's windows are counted from Bluffton's average frost dates. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Feb 27 – Mar 13 | May 1 – May 8 | Jun 30 – Jul 20 | — |
| Pepper | Very tender | Feb 13 – Feb 27 | May 8 – May 15 | Jul 7 – Aug 6 | — |
| Cucumber | Tender | Mar 27 – Apr 3 | May 1 – May 8 | Jun 20 – Jul 10 | — |
| Summer squash / zucchini | Tender | — | May 1 – May 8 | Jun 15 – Jun 30 | — |
| Bush bean | Tender | — | May 1 – May 8 | Jun 20 – Jun 30 | Aug 21 – Aug 31 |
| Sweet corn | Tender | — | Apr 24 – May 8 | Jun 23 – Jul 23 | — |
| Basil | Very tender | Mar 13 – Mar 27 | May 1 – May 8 | May 31 – Jun 15 | — |
| Lettuce | Half-hardy | Mar 13 – Mar 27 | Mar 27 – Apr 10 | May 11 – May 26 | Aug 7 – Aug 22 |
| Pea | Hardy | — | Mar 13 – Mar 27 | May 7 – May 22 | Jul 28 – Aug 12 |
| Spinach | Hardy | — | Mar 13 – Mar 27 | Apr 22 – May 2 | Aug 17 – Aug 27 |
| Carrot | Half-hardy | — | Apr 3 – Apr 10 | Jun 2 – Jun 22 | Jul 18 – Aug 7 |
| Broccoli | Half-hardy | Feb 27 – Mar 13 | Mar 27 – Apr 10 | May 21 – Jun 10 | Jul 23 – Aug 12 |
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USC00120830. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 (p10 for spring, p90 for fall) — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | May 3 | May 18 | Oct 10 | Oct 22 | 157 |
| 32°F (freeze) | Apr 24 | May 9 | Oct 20 | Nov 3 | 179 |
| 28°F | Apr 12 | Apr 27 | Nov 1 | Nov 15 | 202 |
| 24°F | Apr 1 | Apr 15 | Nov 13 | Dec 1 | 225 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 3,091 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 5,270 | cool-season crops (brassicas, greens) |
Hardiness zone 6a
Bluffton sits in USDA plant hardiness zone 6a on the 2023 map — meaning its average annual extreme minimum winter temperature is about −10 to −5 °F. That number tells you which perennials, shrubs, and trees reliably survive an average winter here; it does not set your planting dates, which come from the frost calendar above.
Explore more places in zone 6a, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Bluffton?
- Bluffton, Indiana is in USDA plant hardiness zone 6a on the 2023 map (average annual extreme minimum temperature −10 to −5 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Bluffton?
- The average (median) last spring frost at 32°F is around April 24, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as May 9, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Bluffton?
- The average first fall frost at 32°F is around October 20. That leaves a growing season of about 179 days between the average last spring and first fall frosts.
- When should I start tomatoes in Bluffton?
- Start tomato seeds indoors about Feb 27 – Mar 13 and transplant them outside about May 1 – May 8, once the danger of frost has passed. Estimated first harvest is around Jun 30 – Jul 20.
- How long is the growing season in Bluffton?
- About 179 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~April 24) and the average first fall frost (~October 20). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USC00120830 (Bluffton 6n, 5.2 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.