Casa de Oro-Mount Helix, CA planting zone & frost dates
Casa de Oro-Mount Helix is in USDA hardiness zone 10b. The last spring frost usually comes around January 6 and the first fall frost around December 21, for a growing season of about 350 days.
Planting calendar for Casa de Oro-Mount Helix
Dates are counted from the average last spring frost (January 6) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Nov 11 – Nov 25 Transplant outdoors: Jan 13 – Jan 20 |
| Peppers | Start seeds indoors: Oct 28 – Nov 11 Transplant outdoors: Jan 20 – Jan 27 |
| Eggplant | Start seeds indoors: Oct 28 – Nov 11 Transplant outdoors: Jan 20 – Jan 27 |
| Broccoli | Start seeds indoors: Oct 28 – Nov 11 Transplant outdoors: Dec 9 – Dec 23 |
| Cabbage | Start seeds indoors: Oct 28 – Nov 11 Transplant outdoors: Dec 9 – Dec 23 |
| Onions (sets) | Plant outdoors: Dec 9 – Dec 23 |
| Peas | Sow outdoors: Nov 25 – Dec 9 |
| Spinach | Sow outdoors: Nov 25 – Dec 9 |
| Lettuce | Sow outdoors: Dec 9 – Dec 23 |
| Carrots | Sow outdoors: Dec 9 – Dec 23 |
| Potatoes | Plant outdoors: Dec 9 – Dec 23 |
| Beans | Sow outdoors: Jan 13 – Jan 20 |
| Sweet corn | Sow outdoors: Jan 13 – Jan 20 |
| Cucumbers | Sow outdoors: Jan 13 – Jan 20 |
| Squash & zucchini | Sow outdoors: Jan 13 – Jan 20 |
| Basil | Start seeds indoors: Nov 25 – Dec 9 Transplant outdoors: Jan 13 – Jan 20 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Oct 26 (8 weeks before the average first fall frost on Dec 21).
Useful for zone 10b gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Shade cloth — for hot summers
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Dec 13 | Jan 6 | Feb 7 |
| First 32°F frost in fall is before | Jan 15 | Dec 21 | Dec 1 |
How to read it: in spring there is a 10% chance of a frost after February 7, so that is a safe date for tender plants. In fall there is a 10% chance of frost before December 1. A hard freeze (28°F) usually ends around December 31.
Nearby cities
- El Cajon zone 10a, last frost Jan 6
- Spring Valley zone 10b, last frost Jan 6
- Rancho San Diego zone 10b, last frost Jan 6
- La Mesa zone 10b, last frost Jan 6
- Bostonia zone 10a, last frost Jan 6
- La Presa zone 10b
- Lemon Grove zone 10b, last frost Jan 6
- Santee zone 10a, last frost Jan 6
Questions
What growing zone is Casa de Oro-Mount Helix, CA?
Casa de Oro-Mount Helix is in USDA Plant Hardiness Zone 10b (average extreme winter low 35°F to 40°F), according to the USDA 2023 map.
When is the last frost in Casa de Oro-Mount Helix?
The average last spring frost (32°F) in Casa de Oro-Mount Helix is January 6. There is still a 10% chance of frost until February 7.
When can I plant tomatoes in Casa de Oro-Mount Helix?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Jan 13 – Jan 20. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station El Cajon, CA (USC00042706), 5.6 km (3.5 mi) from the city center, elevation 151 m, based on 27 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.