Glen Ellen, CA planting calendar
- USDA zone
- 9b25 to 30 °F
- Last frost
- Mar 2avg, 32°F
- First frost
- Nov 27avg, 32°F
- Growing season
- 270days
Glen Ellen, California is in USDA plant hardiness zone 9b. Its average last spring frost is around March 2 and the first fall frost around November 27, giving a growing season of about 270 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.
Glen Ellen planting calendar
Each crop's windows are counted from Glen Ellen'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 | Jan 5 – Jan 19 | Mar 9 – Mar 16 | May 8 – May 28 | — |
| Pepper | Very tender | Jan 1 – Jan 5 | Mar 16 – Mar 23 | May 15 – Jun 14 | — |
| Cucumber | Tender | Feb 2 – Feb 9 | Mar 9 – Mar 16 | Apr 28 – May 18 | — |
| Summer squash / zucchini | Tender | — | Mar 9 – Mar 16 | Apr 23 – May 8 | — |
| Bush bean | Tender | — | Mar 9 – Mar 16 | Apr 28 – May 8 | Sep 28 – Oct 8 |
| Sweet corn | Tender | — | Mar 2 – Mar 16 | May 1 – May 31 | — |
| Basil | Very tender | Jan 19 – Feb 2 | Mar 9 – Mar 16 | Apr 8 – Apr 23 | — |
| Lettuce | Half-hardy | Jan 19 – Feb 2 | Feb 2 – Feb 16 | Mar 19 – Apr 3 | Sep 14 – Sep 29 |
| Pea | Hardy | — | Jan 19 – Feb 2 | Mar 15 – Mar 30 | Sep 4 – Sep 19 |
| Spinach | Hardy | — | Jan 19 – Feb 2 | Feb 28 – Mar 10 | Sep 24 – Oct 4 |
| Carrot | Half-hardy | — | Feb 9 – Feb 16 | Apr 10 – Apr 30 | Aug 25 – Sep 14 |
| Broccoli | Half-hardy | Jan 5 – Jan 19 | Feb 2 – Feb 16 | Mar 29 – Apr 18 | Aug 30 – Sep 19 |
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 USC00048351. 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 | Apr 8 | Apr 29 | Nov 8 | Nov 26 | 214 |
| 32°F (freeze) | Mar 2 | Apr 5 | Nov 27 | Dec 21 | 270 |
| 28°F | Jan 20 | Feb 22 | Dec 14 | Jan 17 | 334 |
| 24°F | Jan 1 | Jan 29 | Dec 28 | Jan 23 | 365 |
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) | 3,608 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 6,965 | cool-season crops (brassicas, greens) |
Hardiness zone 9b
Glen Ellen sits in USDA plant hardiness zone 9b on the 2023 map — meaning its average annual extreme minimum winter temperature is about 25 to 30 °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 9b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Glen Ellen?
- Glen Ellen, California is in USDA plant hardiness zone 9b on the 2023 map (average annual extreme minimum temperature 25 to 30 °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 Glen Ellen?
- The average (median) last spring frost at 32°F is around March 2, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as April 5, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Glen Ellen?
- The average first fall frost at 32°F is around November 27. That leaves a growing season of about 270 days between the average last spring and first fall frosts.
- When should I start tomatoes in Glen Ellen?
- Start tomato seeds indoors about Jan 5 – Jan 19 and transplant them outside about Mar 9 – Mar 16, once the danger of frost has passed. Estimated first harvest is around May 8 – May 28.
- How long is the growing season in Glen Ellen?
- About 270 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~March 2) and the average first fall frost (~November 27). 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 USC00048351 (Sonoma, 4.8 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.