Prospect, OR 97604 planting calendar
- USDA zone
- 6b−5 to 0 °F
- Last frost
- May 19avg, 32°F
- First frost
- Oct 3avg, 32°F
- Growing season
- 136days
Prospect, Oregon is in USDA plant hardiness zone 6b. Its average last spring frost is around May 19 and the first fall frost around October 3, giving a growing season of about 136 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.
Prospect planting calendar
Each crop's windows are counted from Prospect'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 | Mar 24 – Apr 7 | May 26 – Jun 2 | Jul 25 – Aug 14 | — |
| Pepper | Very tender | Mar 10 – Mar 24 | Jun 2 – Jun 9 | Aug 1 – Aug 31 | — |
| Cucumber | Tender | Apr 21 – Apr 28 | May 26 – Jun 2 | Jul 15 – Aug 4 | — |
| Summer squash / zucchini | Tender | — | May 26 – Jun 2 | Jul 10 – Jul 25 | — |
| Bush bean | Tender | — | May 26 – Jun 2 | Jul 15 – Jul 25 | Aug 4 – Aug 14 |
| Sweet corn | Tender | — | May 19 – Jun 2 | Jul 18 – Aug 17 | — |
| Basil | Very tender | Apr 7 – Apr 21 | May 26 – Jun 2 | Jun 25 – Jul 10 | — |
| Lettuce | Half-hardy | Apr 7 – Apr 21 | Apr 21 – May 5 | Jun 5 – Jun 20 | Jul 21 – Aug 5 |
| Pea | Hardy | — | Apr 7 – Apr 21 | Jun 1 – Jun 16 | Jul 11 – Jul 26 |
| Spinach | Hardy | — | Apr 7 – Apr 21 | May 17 – May 27 | Jul 31 – Aug 10 |
| Carrot | Half-hardy | — | Apr 28 – May 5 | Jun 27 – Jul 17 | Jul 1 – Jul 21 |
| Broccoli | Half-hardy | Mar 24 – Apr 7 | Apr 21 – May 5 | Jun 15 – Jul 5 | Jul 6 – Jul 26 |
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 USC00356907. 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 | Jun 11 | Jun 28 | Sep 14 | Oct 1 | 95 |
| 32°F (freeze) | May 19 | Jun 9 | Oct 3 | Oct 20 | 136 |
| 28°F | Apr 26 | May 16 | Oct 24 | Nov 18 | 182 |
| 24°F | Mar 17 | Apr 21 | Nov 17 | Dec 14 | 243 |
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) | 2,429 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 4,908 | cool-season crops (brassicas, greens) |
Hardiness zone 6b
Prospect sits in USDA plant hardiness zone 6b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −5 to 0 °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 6b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Prospect?
- Prospect, Oregon is in USDA plant hardiness zone 6b on the 2023 map (average annual extreme minimum temperature −5 to 0 °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 Prospect?
- The average (median) last spring frost at 32°F is around May 19, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as June 9, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Prospect?
- The average first fall frost at 32°F is around October 3. That leaves a growing season of about 136 days between the average last spring and first fall frosts.
- When should I start tomatoes in Prospect?
- Start tomato seeds indoors about Mar 24 – Apr 7 and transplant them outside about May 26 – Jun 2, once the danger of frost has passed. Estimated first harvest is around Jul 25 – Aug 14.
- How long is the growing season in Prospect?
- About 136 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~May 19) and the average first fall frost (~October 3). 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 USC00356907 (Prospect 2 Sw, 37 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.