When to plant Tomatoes in Jefferson County, CO
Plant Tomatoes in Jefferson County, between May 21 and June 11 — the only viable window. Zone 6a's short season (135 frost-free days) rules out a fall crop.
When to Plant Tomatoes in Jefferson County, CO
Tomatoes are the most popular home garden crop, available in thousands of varieties from tiny cherries to massive beefsteaks. They are warm-season plants needing full sun.
Jefferson County, Colorado is in USDA Zone 6a. The average last spring frost is May 14 and the first fall frost is September 26, giving you a growing season of approximately 135 days.
At an elevation of 5,376 feet, Jefferson County receives approximately 22.7 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Tomatoes to ensure they mature before fall.
Jefferson County Soil Profile
Soil Type
Loam
Soil pH
6.0-7.0
Drainage
Well Drained
How Much Tomatoes to Grow
For a family of 4, plant approximately 12 tomatoes plants in about 24 sq ft. In Jefferson County's 135-day season, you'll have plenty of time for a full harvest. Plan your garden layout →
Tomatoes Planting Timeline — Jefferson County, CO
Tomatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 19 | Mar 19 – Apr 2 |
| Transplant Outdoors | May 28 | May 28 – Jun 11 |
| Direct Sow | May 21 | May 21 – Jun 11 |
| Harvest | July 30 | Jul 30 – Oct 8 |
Plant 0.5" deep · 24" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
60–85 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 6a
📆 Growing Season
135 days in Jefferson County
Growing Tips for Jefferson County
Start seeds indoors 6-8 weeks before last frost. Bury transplants deep to encourage rooting along the stem. Provide consistent moisture to prevent blossom end rot and cracking.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 25 ft between varieties for purity. Use open-pollinated varieties for true-to-type seeds.
Tomatoes in Other Locations
Frequently Asked Questions
When should I plant Tomatoes in Jefferson County, CO?
Jefferson County is in Zone 6a with an average last frost of May 14. Plan your Tomatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is Jefferson County, CO?
Jefferson County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 14 and first fall frost is September 26.
When should I plant Tomatoes in Jefferson County, CO?
In Jefferson County, CO, plant Tomatoes after the last frost (around May 14) and before the first frost (around September 26). Best results when soil holds above 50°F.
What growing zone is Jefferson County, CO for Tomatoes?
Jefferson County sits in USDA Zone 6a. Tomatoes grows reliably in zones 3a through 11b, so it's a good fit here.
Can Tomatoes grow in Jefferson County's climate?
Yes — Tomatoes grows well in Jefferson County's temperate climate. Jefferson County averages a 135-day frost-free season, with last frost around May 14 and first frost around September 26.
Your Jefferson County Garden Planner — Free
A 22-page printable planner built for Jefferson County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.