Parker, CO planting zone & frost dates
Parker is in USDA hardiness zone 5b. The last spring frost usually comes around May 9 and the first fall frost around October 3, for a growing season of about 145 days.
Planting calendar for Parker
Dates are counted from the average last spring frost (May 9) 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: Mar 14 – Mar 28 Transplant outdoors: May 16 – May 23 |
| Peppers | Start seeds indoors: Feb 28 – Mar 14 Transplant outdoors: May 23 – May 30 |
| Eggplant | Start seeds indoors: Feb 28 – Mar 14 Transplant outdoors: May 23 – May 30 |
| Broccoli | Start seeds indoors: Feb 28 – Mar 14 Transplant outdoors: Apr 11 – Apr 25 |
| Cabbage | Start seeds indoors: Feb 28 – Mar 14 Transplant outdoors: Apr 11 – Apr 25 |
| Onions (sets) | Plant outdoors: Apr 11 – Apr 25 |
| Peas | Sow outdoors: Mar 28 – Apr 11 |
| Spinach | Sow outdoors: Mar 28 – Apr 11 |
| Lettuce | Sow outdoors: Apr 11 – Apr 25 |
| Carrots | Sow outdoors: Apr 11 – Apr 25 |
| Potatoes | Plant outdoors: Apr 11 – Apr 25 |
| Beans | Sow outdoors: May 16 – May 23 |
| Sweet corn | Sow outdoors: May 16 – May 23 |
| Cucumbers | Sow outdoors: May 16 – May 23 |
| Squash & zucchini | Sow outdoors: May 16 – May 23 |
| Basil | Start seeds indoors: Mar 28 – Apr 11 Transplant outdoors: May 16 – May 23 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 8 (8 weeks before the average first fall frost on Oct 3).
Useful for zone 5b 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
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 27 | May 9 | May 23 |
| First 32°F frost in fall is before | Oct 15 | Oct 3 | Sep 21 |
How to read it: in spring there is a 10% chance of a frost after May 23, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 21. A hard freeze (28°F) usually ends around April 29.
Hardiness zone by ZIP code in Parker
- 80134 zone 5b
- 80138 zone 5b
Nearby cities
- The Pinery zone 5b, last frost May 9
- Lone Tree zone 6a, last frost May 5
- Centennial zone 6a, last frost May 5
- Cherry Creek zone 6a, last frost May 7
- Castle Pines North zone 5b, last frost May 9
- Castle Rock zone 5b, last frost May 9
- Highlands Ranch zone 6a, last frost May 5
- Greenwood Village zone 6a, last frost May 2
Questions
What growing zone is Parker, CO?
Parker is in USDA Plant Hardiness Zone 5b (average extreme winter low -15°F to -10°F), according to the USDA 2023 map.
When is the last frost in Parker?
The average last spring frost (32°F) in Parker is May 9. There is still a 10% chance of frost until May 23.
When can I plant tomatoes in Parker?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 16 – May 23. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Parker, CO (USC00056323), 1.1 km (0.7 mi) from the city center, elevation 1800 m, based on 16 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.